A very rare transmission story

September 17, 2011, 10:20:10 pm

Early June of this year,I had a heat problem with the transmission while traveling across Iowa. All dash gauges were normal but the Silver Leaf indicated high temp in the sump oil. Other abnormalties were low oil read out on the touch pad but the dip stick showed the oil to be 3 " over full. Also, the retarder had a 3-5 second delay when activated. Two calls to two Allison shops that I respected, resulted in responses of, "that's strange", "never seen that before", "that's not possible".

Inland Truck in Omaha dropped the control module out, replaced several things that "might" have been the cause, including the oil level sensor, and the final road test indicated that the problem was solved. For 700-1K miles,everything was normal, but then,,,the old problem slowly started to reappear. Most often after using the retarder on long grades out west. The dash gauges would return to normal but the transmission sump temp would remain very high for many miles and would never return to what I would consider normal. For example: The water temp would be 180 and the retarder temp would be 185 while the trans sump would be 235-247. And, after using the retarder on a hill, the Oil flow to the oil cooler would be about 200 while the main body of the transmission remained at 255. It was obvious that there was a major problem that was getting worse.

I finally contacted Valley Power at Sacramento,Ca. They first checked the easy fixes. Retarder Control valve, solenoids, oil cooler and lines, and finally found there was very little, to no, lube oil pressure to the internal parts of the transmission. The techs at Valley Power and Allison engineers, all agreed that this coach should not be able to make it to the get on ramp, let alone run 70+mph down the interstate. The decision was made to pull the tranny and do a total tear down. I was presented with a 12k+ estimate to sign to authorize them to look for a problem that they ( Valley techs and Allison engineers ) had never seen before and did not have any idea where to look. Note, That estimate included all the research time to solve the problem.

When the retarder housing was separated from the main body, they saw a small piece of the gasket was missing. Immediately there was an "AH HA" moment all around the Allison operating table. ( see attached pictures ). That missing gasket allowed high pressure lube oil to by pass the cooler lines and the oil was being dumped back into the main body. That is why the oil kept getting hot. Why the dip stick read high and the touch pad read low. ( The dip stick is in the main body while the touch pad level sensor is in the control module ). Why the retarder had a delay. (no lube oil pressure to charge the retarder accumulator ). They, and I, were surprised to find no abnormal wear. They did a total cleaning,replaced the usual bronze bushings and thrust washers, rebuilt and did a dyno test. We just completed a three day high speed run from Sacramento, Ca. to Aurora, Ne, and the coach is definitely back to it's normal self.

There are two unanswered questions. Why did the gasket fail after 11 years? Why did it run OK, for several hundred miles after Inland truck rebuilt the control module ?

Also, Remember, all my dash gauges read normal all the time. I originally bought my VMSpc more or less as a new "toy" to kind of, keep me "entertained" while on the road. If I had not monitored everything it had to offer,including retarder oil temp, (a call to Siver Leaf will help you turn it on), I would have had a very expensive tow and repair at where ever. The VMSpc told me there was a developing problem that I could monitor and make a choice as to where I wanted to solve it. That "toy" has made me a more efficient driver and has saved me many thousand of dollars. ( I do not work for Silver Leaf and they do not know I am writing this ).

I am writing this at the extreme urging of several friends. This was a very rare problem that puzzled key people at Allison. It is highly unlikely that any one on this forum will ever see this problem. The HD 4060 MH and the HD 4000 MH transmissions are so rare, that Allison corp no longer carry the rebuilds on their available parts list. FT's are about the only coaches that use them. Don't worry! They will be very happy to build you one if needed. Two week build time +tax +shipping +core charge if yours is not rebuildable + shipping the core back to them. There are some independent shops that may have them but I would prefer to deal direct.

For the record! DO NOT let any of this story stop anyone from buying a Foretravel! I have put several hundred thousand miles on 5 Fortravels, two with retarders,and I will never own a motor home that does not have a retarder.

I apologize that this post is so long but story writing is not easy for me. Maybe, this may help some one some day.

Thank you. Gary O

Re: A very rare transmission story

Reply #1 – September 17, 2011, 11:16:27 pm

Gary,

Thanks for sharing the story and the pictures. Your observations and persistence are remarkable.

I was stunned with the mechanical beauty and cleanliness of an old transmission. The mechanical beast is quite a work of art.

Re: A very rare transmission story

Reply #2 – September 17, 2011, 11:24:49 pm

Gary, Many thanks for the heads up on the Allison issue you faced, I am glad to learn there are two temp senders for the transmission. I was not aware of the second one reading the sump temp. I guess I thought the VMSpc reading was the same as the dash reading, guess that is the retarder oil temp. Anyway I see a call to Silverleaf coming.
Since I turned my ISM into a 500 @ 1550, I like good temp info, both trans and engine.
Again sorry for your misfortune, but thank you for the info heads up.
Cheers
Dave M

Re: A very rare transmission story

Reply #3 – September 18, 2011, 12:22:29 am

Quote from: J. D. Stevens – September 17, 2011, 11:16:27 pm

Gary,

Thanks for sharing the story and the pictures. Your observations and persistence are remarkable.

I was stunned with the mechanical beauty and cleanliness of an old transmission. The mechanical beast is quite a work of art.

I relate the complexity and beauty to my wife. But treat her badly and...

Re: A very rare transmission story

Reply #4 – September 18, 2011, 09:44:59 am

Gary,

Sorry to hear of your misfortune as I had to have my trans rebuilt last year also.

Lassetter Laflour rebuilt it replacing any worn part, any part that had been updated since 1995 was replaced worn or not (the C-4 clutch pack is an example) and they overnighted my retarder ring to Chicago to have the center oversized and a steel insert installed to resize it, making it stronger than new. The Chicago folks did the work the morning it arrived and overnighted it back that day so it was only gone two days.

All work including R&R of trans was $8500 flat fee.

Lassetter Laflour is in Channelview, Tx, on the east side of Houston out I-10. Alan Lassetter's number is 281.457.5003. You all might want to remember the number as like James Stallings, Alan will talk to an RVer who he has never met and discuss your concern. So if you are a long way off and are getting all this info from a shop, call Alan and he will help you sort out what the real deal is and can give you the support to make a good decision on what to do.

Of course if you are nearby, Alan is way better than Stewart and Stevenson, our local Allison dealer.

Re: A very rare transmission story

Reply #5 – September 18, 2011, 10:24:52 am

So can I assume the final cost was a bit less?

Re: A very rare transmission story

Reply #6 – September 18, 2011, 10:30:07 am

Silver leaf now offers a USB connection for laptops. I wish they would come out with a Bluetooth connected iPad app!

Re: A very rare transmission story

Reply #7 – September 25, 2011, 10:51:16 pm

Thanks for the post. I think that Allison has a great unit and I have put on over 300K miles in 10 years or so and will second that I will not have a coach without the retarder. I love it..

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