Allison Transmission Problems HELP!

[GSwaim]

Prevost pulled the HD4000MH today for a front seal leaking to find what I would call one's worst nightmare. The more they looking inside the tranny the worse it got. By the time they got the torque converter apart it was obvious, a remanufacturered transmission was needed. Someone had taken this unit apart that didn't know what they were doing and didn't put it back together right. Consequently all the parts wore heavily and spread metal throguhtout the entire transmission.

I'm looking for a reman for a good price delivered to Prevost Nashville, Anyone know someone with a unit ready to deliver at a good price?

Model - HD4000MH
Part # E004560
Serial# 6610065896

[Jon Wehrenberg]

Here's my free advice based on the presumption you will keep your coach.

Allison rebuilds transmissions and they are warranted as a new one. The advantage of a factory remanufactured transmission is it comes with all the current upgrades. I cannot tell you if the pricing on those is negotiable, but surely Prevost as an OEM can get a good deal on one.

This advice is worth every cent you pay for it.

[GSwaim]

Jon,
Thanks for the advice. I ordered a certified remanufactured Allison from Weller this morning. They seem to have the best network of dealers to take care of any warranty issues if one arises later on. The new Prevost facility here in Goodlettsville is putting it in and "Heavy" thier Allison mechanic appears to be one of the best Allison techs in the nation. He's using his 28+ years of Allison/Prevost experience to ensure all the prevost wire harness, hoses and such are in the best possible condition while we wait for the new tranny to get here.

I haven't found out who but I will, had this tranny out & apart before. They left several signs such as goobered up sensor connectors and galded bolts and such that they had no idea what they were doing. To make matters worse they didn't have the proper knowledge to have this transmission apart and made novice mistakes that destroyed the tranny. It sure is ashame with so few of miles on the original transmission that it was destroyed by this so called mechanic. I guess I should count my blessings that they punctured the front seal while installing the Torque Converter making me remove it and find the tranny was a ticking roadside breakdown. Although I wasn't prepared to hear "this tranny has been ruined," it would have been worse if I had to be brought to the shop on a hook and then told the bad news. all in all, I now know it will be right and can forget this part of the bus for quite some time.

[Jon Wehrenberg]

I think you are doing the right thing.

Your new transmission will have to be programmed (or maybe its the bus that has to be programmed) so the DDEC and ATEC talk to one another and are compatible.

I do not know if you are aware, but you can check the health of your transmission (you cannot, but the Allison mechanics can) to determine all sorts of things, and the diagnostics can be printed out in graphics form. You will have some harsh shifts until you "teach" the transmission your driving style. That will take a number of cycles to smooth everything out, but once that is done you will have a hard time telling when the bus shifts without looking at the tach or keypad.

[GSwaim]

Thanks Jon for the vote of confidence. The new Allison is in place and it is working flawlessly. I’ve learned a lot and one lesson that I will always perform with a purchase of a vehicle is to check the drain plug magnet on all reservoirs. I’ve always examined them when changing oil but not when inspecting vehicles I want to purchase. That would have shown me that the old tranny had troubles and saved me some major dollars. Maybe that should be on the how to buy a Prevost list.

[Jon Wehrenberg]

Gary and others,

Buying a Prevost is not a case where you kick the tires and see if you like the colors. It is a complex event that only begins when you and the seller strike a deal on the price. I think somewhere is a guide (POG home page maybe?) that can be printed out by prospective buyers and in it I talk about having DD and Allison run the codes. You do not have to check a drain plug because it doesn't necessarily tell the whole story. But having the experts connect to a computer and review the current condition and pervious codes will help substantially.

I don't know if your transmission ills would have been detected, but I do know the Allison diagnostics are superb and can tell you a lot about the current condition. They will give you a graphic report showing considerable detail including clutch wear and life remaining. Whether it would show if some hack did poor quality work I can not say.

Pulling a drain plug on the engine or transmission is an expensive thing. Most transmissions have Transynd which is now carrying a price per gallon just slightly below the CA debt level and I am not sure the drain plug on the tranny has a magnet. What I would suggest, which is what we do with planes is to remove a filter, cut it open and examine its contents. You will have far less fluid loss and you will see a much more detailed accumulation of the crud that may be floating around in the fluids. Not all debris is going to be magnetic, such as clutch material and copper or aluminum particles.

[BoaterAl]

Jon, On most large boats we purchased we wrote into the purchase agreement that all fluids would be sampled and examined by a competent lab. Now, before you go on to say that this is not an accurate test let me say this. Something is better then nothing. As long as results show normal I get that warm and fussy feeling about the purchase. On one twin diesel rig, that test showed an very high level of anti freeze in the oil. So the other guy paid for the head gasket job. As much money as one of these buses cost many purchasers won't spend any money on a survey. IMHO the RV industry has done a AAA job of keeping a pre-purchase survey out of coach buying.
AL
05 Marathon XL II (with shield)
010 GMC Acadia AWD

[GSwaim]

I wasn't suggesting the buyer drain the whole crankcase but it's easy enough to drop just a quart at most from the engine and tranny pan wothout a complete drain. The engine would be the tough one since the drain plug would have to be substatuted until you finish checking the drain plug magnet. The Allison would be easy because dropping the primary filter only would maybe make you loose a gallon of transyn. The filter as Jon explained could be inspected for solids and a sample of the fluid could be analyzed for non metalic particles.

I had my codes read by Prevost prior to the purchase and both transmission and engine ran clean with the exception of an ABS fault. No record of any transmission problem or service were detected or ever recorded at Prevost. I detected a leak in the front seal of the transmission prior to buying so I negociated that the seller pay for the R & R of that seal after the purchase. Since the Allison shifted perfectly up to the point it was removed for a new front seal, I had no reason to think it was being blasted with metal shavings throughout the inside. Only a close inspection of the primiary filter and/or an oil analysis would have told the whole story.

[Jon Wehrenberg]

Boater Al, no question an oil sample is better than a poke in the eye with a sharp stick, and an obvious anomoly like coolant in the oil is a sure sign something is wrong. However an oil analysis is most valuable if you can see the results of a series of analysis over time so you can see trends.

Personally, I like the oil filter inspection because when pieces and parts show up in the filter, and they do show up, you don't care what material they are because all you care about is the fact the engine or the transmission is making metal and that signals somebody is about to spend some Lewbucks.

This is like looking for air leaks. There is no single best way, and short of cutting open a filter, having the codes read, and doing an oil analysis I don't know what else can be done to verify condition. And them I am not so sure there won't be a surprise from time to time.

[GSwaim]

Jon,

Agreed there can always be surprises. Short of removing and tearing down the engine and transmission which is cost prohibative, one will never know just what is going on inside. I was amazed that my Allison shifted so silky smooth with the amount of metal I found floating around inside. Prevost Allison tech that has been doing Allisons for 28 years says he sees it all the time but also included in his statement, "when it decides to stop shifting you are on a hook to the nearest shop because it quits all together".

I can also include Weller, the Allison certified transmisssion rebuilders were easy to work with, gave a great nationwide warranty and had the new tranny there the next day when they said they would were great to work with. Overall I'm very please with there work ethic as well as there product.