I cant figure this one out, fresh rebuilt 80e, pi stall. It will shift very hard from park to reverse if I dont let the truck idle for at least 20 seconds. If I let it sit for a minute the shift will be normal, and if I have been driving around a while, put it in park, then back to reverse its fine. Only on the initial startup does it shift hard. Ive checked the fluid at least 4 times on different occasions at different temperatures and its perfect

 

You just can't catch a break.

Hope you get it worked out.

 

mine does this also because the rpms are still elevated at that initial idle

 

I mean, its not a huge issue, just kind of annoying....trans works perfect otherwise.

 

How hard does it actually hit? If you've ever felt how hard an Allison goes into reverse when cold, take that times about five and that will get you in the neighborhood of how hard mine hits on a cold "garage" shift to reverse. Like said the cold start high idle doesn't help things any. Once warmed up mine still hits reverse pretty hard but the converter is really really tight too.

 

Umm, pretty hard, enough for me to worry about it.

Going from park to drive is not a problem, just from park to reverse... I am not familiar with the park to reverse shift mechanism on the 80e, so im not sure if there is anything fragile in there that historically has problems...

 

subing..

 

Did you read the instruction manual?

 

I've seen some issues here. The obvious is just as stated that the idle is higher when the truck is first started and so is the line pressure because of this. Another thing to address is the rear band circuit. An orifice can be installed into the case for the feed for the band. This will help slow down the apply oil for the low band so it does not apply hard. Another thing to look at is the cushion for the Hi/reverse drum. If it has been removed or the inner lip seal has been removed I feel that a harder apply will be felt. This one is kind of a double edged sword. When the trans shift to third normally a builder is going to want the most holding power by eliminating these things. However the apply in reverse is effect from this mod. I would say what you are feeling is normal. If your truck is lifted or you have a good amount of drive line slop, this condition will be more noticeable. HTH Vince

 

I read somewhere that in 97 they changed the low/reverse band servo piston and made it weaker and sometimes the servo pin does punch through resulting in a no reverse condition and otherwise all forward gears work fine. I've seen probably half a dozen with this exact problem. My 80E came out of a 96 and I'm hoping its got the old style piston and I won't be having this problem.