Allison drops in low hard..

[deerhunter7]

My 2002 Allison down shifts into low hard when tranny is cold.., once up to temp it is fine . Thought when I first bought it ,there was a software upgrade that fixed this..Can the soft ware go bad ? Or is there another problem ??

[DmaxMaverick]

Could be just air in the system, from TC leak-down. Somewhat common for 01-02. No big deal. Worse case scenario would be a no-go after a cold start, which is remedied with a restart.

Could also be due for a filter/fluid service.

If it's never had the TCM calibration update, it may be money well spent. Several beneficial updates were added late in 2002. A full calibration (PCM and TCM) should be about 30 minutes shop time. It isn't likely your problem is related to the calibration however, if it's just now showing up.

[deerhunter7]

Had the update for that problem. Seems like it only does it when cold and not all the time. Changed filter at 50,000 and now have 81,000. With warmer weather coming finally , most likely won't happen..

[DmaxMaverick]

50K is too long on the filter. 25K is reasonable, for easy to moderate use. More often for hard use.

This is not the old "clod filter", like in trannies past. It is a real, dedicated, high efficiency full flow filter. It should be serviced as such.

[deerhunter7]

Thanks I'll order up a filter and change it !!!!!!

[DmaxMaverick]

If you can help it, don't buy the filter at the dealer. They can be had at any Allison service/distribution center for $10-15. Napa carries a Wix for a little less. I've used 3 Wix filters now, and they don't appear to be any better/worse than the Allison OEM's. The dealer will get $30-50 from you, for the exact filter you can get from Allison.