Built allison

D

DIESEL_POWER

NGM Diesel
Ok so I have a LML, and got a built trans, all is well except one thing, it goes into reverse rougher than it should. Almost like a soft slam into reverse. I was told by the builder it was normal, but it's so bad that the engine down pipe hits the fire wall on occasion because of this when out into reverse.

I put on over 40 k on it and changed to synthetic fluid and new filter, this seemed to help, but still pretty noticable.

Only thing that seems to help is leaving it in neutral for a few seconds before going into reverse.

Any ideas?
 
Wade, I don't have suggestions for the trans issues, but if your engine is moving that much your factory motor mounts are probably shot. You need to install a set of the Merchant Automotive motor mounts which are also available from several other vendors in colors other than MA Orange...
 
could be too tight a stall on the converter? If it is really lugging the engine down at idle, it is a big change from drive to reverse.
 
Wade, I've had a built tranny/converter in my LML for 35k miles and have never noticed that issue on my truck. I don't have an answer on what could be causing it, outside of a very aggressive converter. Do you have a stock TCM tune in it, or one modded for increased PSI?
 
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The mounts are fine, it only jams in gear in reverse, no other gear or selection. Rob, yes the tcm was modified for extra rpm when towing using the exhaust brake, that's the way it was explained.
 
For giggles, I'd throw the stock tcm tune in it. If you didn't do the tcm tune yourself, then it's unknown if line pressure was played with. Increased TCM controlled pressure coupled with VB mods when the tranny was done, may not be playing nice.
 
Maybe a mainline pressure shim with the spring would increase the pressure in the reverse...you could tune for a slightly lower idle and that would help some


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