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Transmission retarder plate leak

November 18, 2012, 12:29:20 am

I noticed an occasional small drop of "oil" on the floor beneath the back of the transmission.  It concerned me so I had mechanics and technicians look at it.  I had checked fluid level, no detected loss. 

Mike Rodgers checked and found nine bolts at about one quarter the spec torque required so he tightened them to specs.  They then soaped and pressure cleaned the tranny, I drove and then crawled under several times to monitor the clean surfaces.  The fluid seep around two bolts was visible, the tightening did not solve.  Maybe more than the two bolts were involved, there are quite a few more than nine there.

Took the coach to Stewart and Stevenson.  When I got there, about 100 miles, and parked, we noted the leak had increased from a drop or two, so timely to have looked at this. S & S took it apart and found three gaskets of the retarder plates needing to be replaced.  Photos of the bolts that were loose and the seep around them are attached.  Maybe it would have continued many miles just leaking a little but that would have worried me. 

Maybe check these every, oh, 140,000 miles?  Mike

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Re: Transmission retarder plate leak

Reply #1 – November 18, 2012, 08:29:40 am

Thanks, Mike for the excellent job of documenting this for all of us.

Were the three offending gaskets on outside plates that could be owner changed, or were they internal to the retarder?

Brett

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Re: Transmission retarder plate leak

Reply #2 – November 18, 2012, 02:29:20 pm

Brett, you are right to ask.  I understood that there were two not so hard to do but one internal.  I will try to ask James at S&S but he was so very very busy both times I went.  Great, understanding folks, just so busy.  Thought would take a day to do this but found they were short one of the gaskets so had to get that one, stretched job into a week.

I asked Nacogdoches motorhome folks if they would do the gaskets, replies were that could not be totally sure that was the only problem and they were not sure that if you started pulling off plates would there be "37 springs fall out"? urged me to go to specialist.  But you raise a good question, I will ask James.

Brett, the bolts that Mike Rodger tried to tighten had loosened to about 10 (whatever units of torque) and the S&S people, trying to help before Jackie and I took it to them, said specs required 38 - 45.  Mike tried that but to no avail.  You would best judge and advise our readers whether an owner should perhaps as preventative maintenance just check the tightness of those before a leak develops.  Eight of the nine were way below specs just on one plate.

Thanks for your interest and after James gets back from a week off at S&S I will call for his ideas on DIY. 

MIke

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Re: Transmission retarder plate leak

Reply #3 – November 18, 2012, 10:15:19 pm

Thanks, Mike. Let us know what you find out.  And when if you find the torque units and which bolts in your photos they apply to, I'll check a few and see if they are loose. 

Could be inch-lbs or ft-lbs-- BIG difference! Guess it could even be newton-meters.

Brett

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Re: Transmission retarder plate leak

Reply #4 – November 20, 2012, 03:04:55 pm

Mike, your reference to torque values of 38 to 45 is almost certainly lb ft, which is referenced frequently in Allison's Service Manual.
But I suspect the correct torque values for the bolts securing the three gaskets is different (see attachment). I'm guessing the three gaskets are items 61, 63, and 65 with item 86 being the related bolts on the exploded view. I am not very good at interpreting these, so perhaps others can comment on torque values and whether these are considered external or internal. On the attachment "torque values specified are for dry assembly, except when otherwise noted. Wash and dry bolts and washers before assembly."
Am sure glad you got this taken care of before it caused any serious problems. Dick

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Re: Transmission retarder plate leak

Reply #5 – November 20, 2012, 04:42:18 pm

Hi Dick,
  So bolt number 86 requires 18-21 lb ft of torque according to note D. Is this how you read this?
Thanks,
Raymond

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Re: Transmission retarder plate leak

Reply #6 – November 21, 2012, 01:17:30 pm

Yes that's what I thought too. That module may not be where Mikes leak was. I was just searching through the manual looking for an illustration of the bolt pattern like his photos. I couldn't find one and sort of stumbled on this. I figured in any case this info might be helpful to someone sometime.
One of the methods they describe for finding a leak was interesting; "The Powder Method. Clean the suspected area, apply an aerosol-type white powder, such as foot powder, to suspected area, operate vehicle under normal conditions, visually inspect suspected area and trace the leak path over the white powder surface to the source." FWIT
Dick

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