Convert from 8V-92 to Series 60

I am considering swapping our 8V-92TA to a series 60. Our coach is a 1990 40' Liberty Prevost. The throttle is by wire, not sure if it is the same as series 60. Does anyone know if the HT750 trans will mate ? Does the Allison HT750 ATEC system mate with the series 60 DDEC 4 ? Will the harness from the DDEC 3 on the 8V-92 work with the DDEC 4 series 60 ? Is the 8V-92 rotation the same as the truck Series 60 ?
Lots of questions, not sure if someone here knows the answers or I need to check with Detroit Allison.

I have seen 40' Prevost with the series 60 so I assume the clearance is there. There is a panel that can be removed in the floor behind the bed that looks like it would allow the clearance.

I know we will get some "why don't you just trade up to a series 60". But we love the floor plan, Liberty quality, colors and real wood bleached oak cabinets. All the newer coaches seem to have the laminates. Just not what we want. Also we have a series 60 engine available.

The 8V-92 runs great and has had the 500 HP upgrade. It runs circles around the series 60 coaches I have tested. Just concerned with the MPG and would like to swap engines prior to some lengthy travel.

Hi Robert,

This is a great set of questions to post on http://www.dieselenginetrader.com/di...es.cfm?catid=9.

Robert,

You need to drive a few more Series 60 coaches. I've had two since I had the 40' with the 8V92 and either one of them would hammer the 92 in every category - except sounding cool. Between the low end torque and the big fuel mileage improvement I would be hard pressed to own anything else.

As for the swap, I have to think you'll need to break out the chainsaw for the back closet.

Prevost was unable to install the Series 60 into a 40 footer until the shorter "World" transmission (the 6 speed) became available due to the increased length of the engine / transmission duo.

I also believe the tag axle geometry had to change, but I am not sure of that.

My reaction is that must be one hell of a Liberty that makes the swap justified compared to just going out and buying one with the Series 60 already in place. You should run the numbers. I am not sure you will escape interior changes as Jerry suggests. Our 87 Liberty had a north/south bed and the only impact of the higher Series 60 would have been to change the flat access cover under the bed to a "dog house", but if you have an east / west bed the cabintery across the back may also be affected.

I am not sure I buy into the theory that the Series 60 is a more powerful engine. It has more low end torque, but once the 8V92 comes alive (over about 1500 RPM) if does quite well. That may be attributable to the 5 speed transmission hanging in gear to 2100 compared to the 6 speed which will shift long before the engine is wound out unless you manually shift it. The only advantage I can see with the Series 60 apart from the low end torque getting you moving quicker from a stop is the fuel mileage, but the cost of converting will require a lot of miles of fuel savings to before those savings are realized.

Robert,

I know some "Bus Nuts" who have converted seated coaches to motor homes. Some of these bus nuts are incredibly talented. I have seen old buses turned into works of art. I have seen old 6V's and 8V's replaced with Series 50 and 60 engines and with Big cat engines. In every case, the owner said it was a lot of work and expensive to covert the engine over. Cooling, wiring, engine and transmission mounts, custom fabrication, possible vibration issues if not mounted correctly, the list goes on. I'm sure it can be done, I even saw one that used a manual transmission, if I remember correctly had 9 gears. But in every case the owner said it cost more then they had planned and took a lot longer to finish the job then they ever thought. Just a thought, how about having a "Hot Rod" 8V built and replace the engine you have now? Simple remove and replace, add water misters to the radiator to remove extra heat. Drive it like you stole it, and put the original engine back in when the hot rod engine melts down. That last line was "tongue in check":)

Whatever you decide, I sure it will be an interesting project,. Take lots of pictures and post often so we can follow along.

Robert, I am a long, long way from being very knowledgeable concerning Diesel engines, etc. but, in this change out you are contemplating, the knowledgeable guys are mentioning cooling. I replaced (recored) my radiator this past fall on my 8V92T and got by very cheap at $2000 final. If that gives you an idea on the associated costs, let alone the cost of the S60, then good luck.

Thanks for all the input, the 8V92 that is in it now is 500 HP and only has a little over 25000 miles. It was replaced by Detoit Allison by the previous owner because of a rear main leak and is a Reman, runs like new. All is documented. We would like to put alot of miles on the coach in the next few years and it looks like fuel is on a steady rise. The best mileage we have achieved is 6. And that was with a bit of a tail wind. Usually around
4-5. I keep hearing of 7-8 with S60 in a 40 footer. Does this sound accurate ?
I have a S60 470 HP which helps with the $$ part. The radiator is in excellent shape and oversized for a S60 according to what I read. I have a fab and machine shop at home. The bed is crossways so there would be a higher floor height behind it but the cabinet base starts at the top of the floor removal piece so I think they would remain untouched. I looked at a similar coach with a S60 and the floor is not an issue. My only hold up is the transmission concern, and wiring harness.
John mentioned a length difference between HT750 and World 6. If this is true then that would be the stumbling point untill I can find a trans.
The amount of work is not an issue since I am retired, we have some heavy dirt equipment and have built several street rods and hot boats. I have the equipment to handle lifting and positioning the heavy engines and trans.
As I said before, we love the coach, and also love the 40' length. We have looked at several 40 footers with S60's, the last one was at Parliament. Paul offered me a hell of a deal on it, but the interior was dark laminate and the conversion was different from our Liberty. We just have not found another 40' Liberty S60 that suits our taste. I know the engine swap is not like dropping a small block chevy in a 32 hiboy, but I think it would be a nice project if the trans and wiring can be figured out.

I do not know this to be a fact, but since Robert has the 500 HP 8V92 it is probable if the HP increase was a factory increase his cooling system has ample capacity. Detroit will not approve an engine installation (read that to mean stand behind any warranty coverage) unless they have approved the installation with respect to cooling.

My guess is the heat transferred to the cooling system from a Series 60 of similar HP is the equivalent of what the 8V92 puts out. The key to doing the swap, before any costs are considered is the physical space required for a taller, longer engine, and if the engine can be paired with a 6 speed transmission to make the fit. My brain is still wrapped around the tag axle configuration needing to change also, but I cannot be sure that is the gospel.

Thanks Jon, and sorry for the mis spelling earlier.
I appreciate the reply, you sound like you have had a lot of experience and that is what I was hoping to tap here. I never thought about the tag being an issue. I may have to crawl under the coach at Parliament.
The 500 HP upgrade was done by Jacksonville Detroit Allison and you are right, that was as high as the factory would allow for that configuration. They were the folks that told me the radiator for an 8V92TA actually had more cooling capacity than for a S60. I guess the 92 series create more heat because of firing each revolution ? I know they are more heat sensitive and have always kept a close eye on the pyrometers.
The front compartment in our coach has two boxes and ports for checking the ADEC and DDEC systems and the harness runs to the rear. I need to know if this harness will plug into a world trans and a DDEC4 ? I am thinking as I am typing this, I can check the DDEC4 on the S60 in my yard now and compare to the DDEC 2 on the 8V92.
I am searching online for a world trans to see what is available and what the plug looks like. Will also visit Detroit Allison tomorrow morning to see what they have to say. Maybe an adaptor or rewire new plugs if wires are the same.
I will also call Prevost in Jacksonville tomorrow to check on the tag axle issue.

As to your question about fuel consumption. I have heard some of the claims of 7-8 mpg, which sounds amazing to me. My S60 regularly performs at about 6.2 mpg. I have tried driving slower and several use combinations to see if I could improve this and found that I really couldn't, within a margin of error. I have a friend with the same basic coach as mine and regularly gets about 5.5 mpg. When you consider the thousands of gallons of fuel that you'll have to use to make up the difference I am not sure that it will pencil out.................

Tony,
I wondered about that, if the mileage is that close it would not be worth it. And I quite frankly love the sound and performance of the 8V92. Your coach is probably a 45' which may make some difference. I assume you flat tow your Jeep Liberty which should be next to nothing in weight and wind. Our Liberty weighs 43000 lbs. and with the smaller trailer and our diesel beetle we can get about 5 mpg. We need the enclosed trailer because we put the Harley in front, but we sometimes tow a stacked trailer that adds another 9000 lbs. If we travel out West we plan on taking the stacked trailer so we can take the toys. That drops the mileage to 3-4 which is where the S60 would maybe help with its torque. I would like to see what a 40' prevost S60 pulling a stacked trailer gets for mileage.

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Originally Posted by antioch01

The front compartment in our coach has two boxes and ports for checking the ADEC and DDEC systems and the harness runs to the rear. I need to know if this harness will plug into a world trans and a DDEC4 ? I am thinking as I am typing this, I can check the DDEC4 on the S60 in my yard now and compare to the DDEC 2 on the 8V92.

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Robert,

There's a bunch of very knowledgable DD folks over at: www.dieselenginetrader.com. Go to the DETROIT subforum. There's a man there who goes by the name of gonefishen. He's a wealth of knowledge as are many other folks over there. They can answer your questions related to ECM and wiring harness compatibilites, etc.

Headed there now, thanks

Robert, I will let the experts address the DDEC issues. When you look at your underside. compare the length of the driveshaft between the U joints on your 8V92 and a Series 60 40 footer. Also see if the tag axle has been modified. I think it is very important to maintain the geometry Prevost built into the 40 footer with Series 60 to avoid vibrations and the damage than can ensue.

As to the mileage, why don't you run some numbers. For example, let's say you drive 15,000 miles. My 8V92 was geared so top speed was 69 MPH, 72 downhill. I drove it at around 60 MPH and I got 5.6 MPG. My Series 60 coach is 5000 pounds heavier, and I drive it 62 MPH and originally got around 8 MPG, but since the change in fuel to the low sulfur I more consistently get 7.5 MPG. These are not guesstimates, but actual numbers since I record every gallon of fuel ever put into the coaches. How you drive will have a substantial impact on your fuel economy.

So lets pretend fuel costs $5.00, which is much higher than it is today. On my 8V92 my fuel cost would have been $13,393. On my Series 60 my fuel cost $10,000 for a savings of $3,393. Now that is not chump change, but if you drive less than the 15,000 miles the savings, even at $5 per gallon is not so significant. Only you can decide if the cost and effort to swap engines and transmissions will be justified based on fuel savings. In today's dollars the savings, even at 15,000 miles per year is down to $2375.

If you are right about fuel going out of sight, maybe you can justify it, but your biggest expense even with a coach of your vintage is still going to be depreciation. Personally, we loved our 87 Liberty and had no intent to replace it, but when it was damaged by a fire and we faced 9 months without it, we bought our current 97 45 footer and will never go back to a 40 footer. The changes Liberty made in the 10 model years was significant and despite how much we liked our 87, it just could not compare.

I second the notion that you may not see the increase in mileage you are looking for. My S60 usually gets around 5.50 to 5.75 mpg. I have only seen it better if I drive much slower than I the speed limit. If you have a working 8v92, I would think you would be hard pressed to ever recover any of the costs involved in a swap just in fuel. FYI, my 45' weighs in at just under 51000 lbs. and I flat pull a 2010 Tahoe.

Hi Mark,

As I'm sure you're aware, the emissions controls on the later S-60's do have a cost in terms of fuel mileage; nonetheless, Robert made it very clear in his earlier posts that he's a talented fabricator with a complete fabrication shop at his disposal and that he likes his bus and wants to keep it. This is great project and will provide a wealth of information and expertise to the forum. I'm looking forward to lots of pics. Robert, good luck!

Thanks to all for the great input. I am definately looking at this project with eyes wide open. Having the S60 for 0 $$ is a plus but if I have to swap trannies to a world the cost could be prohibitive. After reading several threads from the Diesel Talk forum it sounds like the world trans is needed. I did some measuring today and the clearance is not an issue. The length of the S60 to the trans looks like it needs about 3 to 4 more inches, like Jon said earlier.
As a plus though the engine rotations are the same.
Another issue I noticed today was the intercooler needed for the S60. More to think about.
I am going to raise it up tomorrow and look at the drive shaft, tag and trans mounts.

This may have some real information you need. Scroll down to "HardHeadKens" post.

http://www.busconversions.com/bbs/in...topic=12909.15

I forgot to mention my Series 60 is DDEC III. Mileage figures you should rely on are for those who have DDEC !V. Later versions had different mileage. It may in fact turn out the improvement in mileage may not be so great, but with the Series 60 there is one distinct advantage. While a guy is waiting for the 8V92 turbo to spool up the Series 60 with its low end torque will get the bus and that stacker off the line and moving.

And welcome to POG. I hope you know by now we will always answer your questions, and on certain rare occasions we may actually offer the correct answer. If you don't take any of us too seriously, and don't mind hanging out in this asylum we call POG you will fit right in.

Jon,
I have run some numbers and if I pulled my small enclosed trailer with diesel VW beetle, I can get about 5.5 MPG and I would not be as interested in the swap. My concern is when I load my stacker (which is what we would like to take out West) my MPG drops to 4 at best. I do run 60 - 65 MPH. If I can pull that trailer and get 7-7.5 MPG I would be happy and say it was worth it. Not to mention the value of the coach would be better. If I do the conversion I intend to make the S60 look factory or better. The issue with the 45' in my mind is the extra 5000 lbs. My stacker is 9000 lbs. but only adds 4000 lbs. if I deduct the extra 5000 lbs of a 45'. So I should be able to get the same mileage and performance as a 45' pulling a 4000 lbs. vehicle.

The hills out west will not allow you to get 7-7.5 unless you are willing to slow down.

Speed equates to a headwind and with headwinds or speed the mileage goes in the dumper. Add in hills and no matter how much fuel you save going downhill, it never makes up for what you burn going up. Exactly how much impact depends solely on how fast you are trying to go. I have a retarder, so on my downhill runs I dropped it down to 4th and held the speed to 55 because the steeper grades would have been tough on the brakes. That may have impacted my mileage also. Going up those same hills in the opposite direction I was lucky to see 55 so you have some idea of the grades that were impacting my mileage.

Your OTR will take a few tenths of your MPG, so the bottom line is when we travel in the west with our 46,600 pound coach towing our H2 Hummer we weight 53,000 plus and are lucky if we can get 7 MPG. When we went west on our last trip not towing, we got 7.3 for the approximately 4000 mile round trip.

As much as I hate paying for fuel, I just accept the fact that whatever it is there is not much I can do about it, and not using the coach as much as we want to compensate doesn't make sense.

Thanks Andre,
That was quite a discussion and alot of info. We use to subscribe to Bus Conversions when we converted our first Eagle. I thought they went out of business. Sounds like my tag axle is going to prevent the B500 trans from fitting. Guess I will scrub the idea for now until I can figure something out.

Jon, thanks for the welcome, I am very happy with the content of this site. I look forward to enjoying the discussions.

Maybe keep the 8v and install a two speed rear end, just sayin.

JIM

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Originally Posted by travelite

Hi Mark,

As I'm sure you're aware, the emissions controls on the later S-60's do have a cost in terms of fuel mileage; nonetheless, Robert made it very clear in his earlier posts that he's a talented fabricator with a complete fabrication shop at his disposal and that he likes his bus and wants to keep it. This is great project and will provide a wealth of information and expertise to the forum. I'm looking forward to lots of pics. Robert, good luck!

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Yep, I too think it would be pretty neat *but* if Robert is planning on a big fuel gain, I wanted to let him know it *may* not happen. Lots of variables in this equation that are not clear.

Robert,

I suspect your bus is your hobby because you are a gear head like me. I won't get into it to the extent that it sounds you are willing, but I like taking on various projects on the bus, each one being a learning session.

Don't misinterpret any of my remarks as negative concerning the swap you are contemplating. I think you would get a lot of pleasure and satisfaction doing it, and even if the economics don't make much sense today you will have gained a wealth of knowledge. Yes you will have to deal with a lot of issues, ranging from the small ones like making sure the accessories and their belts are lined up and your new dimensions don't force you to start relocating things like the compressor or the fan drive to line up with the engine pulleys, to changing out the cooling fan to a 2 speed fan to fitting the intercooler, to possibly changing out the rear doors to those with cooling slots. Lots of work, probably lots of Lewbucks, hours of effort, but an end result that would make anyone proud.

Some of us not only drive our buses, but we spend hours working on them.

I lean towards Jon's last post as far as what you will reap in satisfaction & knowledge enhancements. Just one last thought not brought up, what cha gonna do while the bus is down? Sounds like you enjoy time spent traveling, any idea how long this will take to bring to fruition once begun?

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Originally Posted by Mark3101

Yep, I too think it would be pretty neat *but* if Robert is planning on a big fuel gain, I wanted to let him know it *may* not happen. Lots of variables in this equation that are not clear.

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Mark, after re-reading my post this morning I see that I may have come across a bit strong, sorry.

Over on the Wanderlodge forum, WOG, we have members contemplating swapping their two-strokers for S-60's. We have one thread happening now where a 6V92 is being swapped for a Cummins 8.3.

Have friend that is in process of installing S 60 in 87 prevost. Hes very knowledgeable on the matter. His name is Ken Arnold and he said he would be glad to answer any questions you might have. 615 2104963. I also told him he needed to join POG> He said that he was. Im 1 yr old on POG> Have a good day.

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Originally Posted by travelite

Mark, after re-reading my post this morning I see that I may have come across a bit strong, sorry.

Over on the Wanderlodge forum, WOG, we have members contemplating swapping their two-strokers for S-60's. We have one thread happening now where a 6V92 is being swapped for a Cummins 8.3.

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No problem...I like to see what everyone else is thinking on things like this. Whatever he does, I hope he has good luck!

Well, I made some calls today and it seems that the tag axle is the deciding factor. Prevost Jacksonville pretty much echoed Jons thoughts about the 6 speed world trans size, and the tag axle configuration preventing installation. There is an "auto shift" trans that would work but it does not have the performance of the B500 world trans. Also the wiring harness would have to be modified with new plugs. My axle ratio is too low and would need to be replaced if not using the O/D world trans. All in all I am a bit dissapointed, but then again it is not like the 8V92 is tired or needing work. Quite the opposite, it runs like a new one. So for the time being we will run as is and make a trip out West to see just how bad or good the mileage is.
If anyone comes across a nice 40' Liberty 96 - 97 let me know. I would hope many folks would like to trade up to a 45' and let their 40' go. We would prefer light oak cabinets but I know most of them are the laminates and we may have to settle for that.
Thanks again for all the support and info, I appreciate the negative as well as the positive comments, that helps me look at things from many perspectives.

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Originally Posted by Jeff Moody

Have friend that is in process of installing S 60 in 87 prevost. Hes very knowledgeable on the matter. His name is Ken Arnold and he said he would be glad to answer any questions you might have. 615 2104963. I also told him he needed to join POG> He said that he was. Im 1 yr old on POG> Have a good day.

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Thanks Jeff, I am going to call him in the morning just to see if he agrees with the info I have so far. Maybe he has figured something else out.

Hi Robert. i was just going to say it would be a lot less money and trouble to Purchase a newer Coach with the Engine ,and drive trane you want and do a remodel to the interior to get what you like.
As far as mileage, Mike Simmons was getting 8 MPG towing his car going out to Kerville last year. He has a 45 foot , 1999 Marathon.

We have looked into a newer coach, unfortunately the only 40 footers are 96-97 models and very few of them available, which means limited features we want. Remodeling the interior is cost prohibitive. The rest are 45 footers and we do not want the length and additional weight. Still looking though.

Jeff, I did call Ken Arnold. What a wealth of knowledge. He is using an "Auto-shift" trans and is almost finished. Should be on the road in a couple of weeks. Waiting to see his results.
Thanks much for the resource. We talked for almost an hour.

I am sure you have seen it but Ken Robertson has a 99 XL40 and its a Liberty. Surprised he hasn't chimed in. Although it is a laminate interior it is a nice color.

Hey Jeff Moody: In case you didn't see the Oysterfest Post I/we need more Tennessee boys to show up at Bella Terra to help eat oysters. We got some coming from east Tennessee, need at least one from the Mid Tenn area!

L.A. (lower Alabama) should be warm (warmer) by mid March than Rockvale.

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Originally Posted by antioch01

We have looked into a newer coach, unfortunately the only 40 footers are 96-97 models and very few of them available, which means limited features we want. Remodeling the interior is cost prohibitive. The rest are 45 footers and we do not want the length and additional weight. Still looking though.

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That's exactly how I felt. I even built my bus garage with a pit based on our 40 footer. Nothing will ever make us go back to a 40 footer even though my garage is now cramped and it is a pain getting into the pit. That extra 5 feet makes a world of difference, and the Series 60 makes up for whatever extra weight I am dragging around.

Lee - Thanks for the post, but the '99 Liberty is sold and just delivered this week - Got to update my website today - I do just happen to have the nicest 40' Royale in the country, and it's owners want to resign their membership in the TBC. ( make an offer !!! )

Ken

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Originally Posted by antioch01

We have looked into a newer coach, unfortunately the only 40 footers are 96-97 models and very few of them available, which means limited features we want. Remodeling the interior is cost prohibitive. The rest are 45 footers and we do not want the length and additional weight. Still looking though.

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How about one of these two? They are at Panterra Coach, where we bought our 01 American XLII. Great folks to deal with. Talk to Bob Makin, tell him I sent you.


http://www.panterracoach.com/index.php?id=36&data=20

http://www.panterracoach.com/index.php?id=36&data=30