So i recently picked up a 98 zr2, truck runs great for 194k. The trans 1-2 shift is really firm and quick and the rest are very quick shifts, that is based on the 3 other s-series trucks i have sitting in my driveway, i do not see any problems there. Overdrive is the issue unfortunately. doing about 40-50 mph on a level road the trans is consistently going in and out of OD very rapidly. for example, as soon as it shifts into OD it takes it right back out then in then out etc even though my speed is consistent nor climbing any hills.

does anyone have any idea on why it would keep searching for OD? eventually after driving a few miles i can get it to settle down but its still searching. fluid is dirty but not burnt, im not changing it because im afraid that will be the death of a good trans. The previous owner said it was the original trans. I doubt that highly, im guessing the trans has about 90k on it. no cel either.

 

Sounds like its just dirty. You need to do the filter/5 quart pan change. dont do a flush,just the pan change. It shouldnt hurt it unless you flushed the whole system. Also replace a quart of fluid with a quart of lucas trans. Great stuff.

 

I have a 98 blazer with 202,000 and my trk was doing the same thing, ordered a lock-up, o.d. Solenoid & cured the problem, pretty easy fix & the solenoid cost around 55.00

 

my 96 has a problem starting out i Overdrive. Currently starting out in 1st, 2nd then drive. What is this 'lock-up'? And which Solenoid is the OD?
Thanks for any reply

 

I have this same issue yet to find the cure, changed fluid and solenoid still does the same thing.