6 Speed Allison transmissin

I had the same hard down shift problem from 4th to 3rd when I changed out the fluid to full synthetic and the transmission did not recognize the fluid so I had a Allison dealer reset the transmission back to factory spec. so it could learn how to shift all over again. I believe they call it resetting the fast adaptive in the Allison computer.....

4 to 3 is always more jerky that most other downshifts. If it were me I would check and see if the trany fluid and filters needs changing.

retiredtravelers2013 wrote:
Hi to all fellow travelers,

My wife and I recently purchased a new to us HR diesel pusher. It is a 98 with a Cummins and the 6 speed Allison tranny. In general the transmission shifts very smoothly. However when under load and shifting from 4th to 3rd it jerks quite a bit. This is the only downshift doing this.
Thank you for any and all help.

FIRE UP wrote:
Ct,
While I wouldn't be too concerned, a call to Allison or, to a service center for Cummins/Allison of your choice might settle your mind. Ours does quite often, a harsh 5-4 shift, if, conditions are just right. If we're cruising in 5th in a grade and slowly loosing speed, enough to cause the trans to jump to 4th, it can sometimes "jerk" the beast around a bit. Remember, the available torque at a given RPM, can and will be felt during some shifts.

On the up shifting, most of the time from 1-2-3-4-5 and finally 6th, it's usually pretty darn smooth but, it's on the down side that, can cause a bit of a shake every now and then.

Exactly the way ours works.

Thanks for the replies,
As I mentioned it only happens under heavy load, as when going up a hi in 4 th then shifting down to 3rd,when just slowing down due to traffic it shifts smooth as silk.
So far we are very happy with this engine combination. We have only been out a few days but plan a little stint at home then seeing the rest of this beautiful country.
Again, thanks for the replies.

Ct,
While I wouldn't be too concerned, a call to Allison or, to a service center for Cummins/Allison of your choice might settle your mind. Ours does quite often, a harsh 5-4 shift, if, conditions are just right. If we're cruising in 5th in a grade and slowly loosing speed, enough to cause the trans to jump to 4th, it can sometimes "jerk" the beast around a bit. Remember, the available torque at a given RPM, can and will be felt during some shifts.

On the up shifting, most of the time from 1-2-3-4-5 and finally 6th, it's usually pretty darn smooth but, it's on the down side that, can cause a bit of a shake every now and then. I've got friends who changed from Dexron to Transynd and said the shifting is seriously smoother.

Well, I did the "$250.00" change over to Transynd and, it shifts exactly like it did before. So, again, maybe a call to whatever service center or, Allison might be warranted.
Scott

Mine does too. doesn't seem to hurt anything.

You can call Allison or check the Allison thread here:

http://www.irv2.com/forums/