I have a 2001 Chevy bus. It has an Allison 2000 transmission. About a year ago, it began having a harsh downshift from 4th to 3rd. Transmission was torn down , looked like new. Replaced solenoid B & E, inspected and tested clutches 3,4, and 5. I use Transsynd fluid since new. Problem still was not solved and is getting worse all the time. Now I am starting to have periodic rought downshift from 5th to 4th. Any ideas?
I'm going to give this thread a bump. My question to you is, have you consulted with your Allison dealer or was this teardown done by an independent shop (or by your shop?) Seems like something they may have seen in the past. Automatic transmissions are the black holes of vehicle repair, IMHO.
"Growing old is mandatory. Growing up is optional."
I am still having periodic rough downshift from 4 to 3. Even had new computer for transmission installed. My mechanic is an trained Allison mechanic. Seems to only have rough downshift during hot weather anything above 70 degrees. Have checked line temps oil line coming out of trans. 170 degrees oil line going into trans. 106 degrees. Any ideas what is causing this problem?
It is my understanding that the 2000 series transmission operates at full torque converter lock-up in all gears above 2nd. If the transmission is programmed for a "lift throttle downshift", that should occur at 2000 RPM. If it is occurring at a higher RPM, I would think that the may be a fault with a speed sensor. Have you hooked up the Allison diagnostic tool to check for faults. The trans warning light may only stay on for hard faults.
Harsh downshift on allison 2000
Posted - 08/29/2012 : 8:47:40 PM
