Returning from the beach the other month, my Yukon suddenly starts to "clunk" into 2nd from 1st gear. It's very noticeable and you can really feel it kicking into 2nd, and only seems to happen when we have a trip that is over 150 miles long. Around town, it is fine. It did it again yesterday after taking my daughter to college, but then went away. Now, the "service engine light" did come on both times it did this, and is still on from yesterday. We did take it to our local repair guy, who can't seem to make it duplicate the problem. Is this a tranny problem, should I just take it to the dealer or a trans shop to diagnose?

Thanks

I had the same problem but mine only had about 43,000 miles on it when it happened. My transmission shop did a valve body upgrade because the miles were low. I wouldn't recommend it to very many people as when my truck is cold it now takes a long time to shift from 1st to second. Cost me about $275 plus I had a better transmission cooler put on total was $400. Take it to a good transmission shop the check engine light puts out a code of 1870 (I think???) they can check it and tell you.

Most dealers will automatically rebuild it costing you BIG $$.

This is very common in the 97's from what I hear (yeah, now that I bought one)

I just had the same thing happen on my 96 Yukon. Same code. it clunked as I turned off a road into a parking lot (slight bump). I checked the trans fluid, and it did not appear normal. very thin, and some bubbles. did not look like it was on the dipstick at all. I added about 4/5 of a quart, and it appeared okay. trans seemed to shift better.

I drove it another hour or so before parking for the night. drove another hour the next morning and took it in to a Pep Boys. (only thing open). found the code and that the tranny was overfilled by nearly 2 quarts.... (I just bought this truck 5k miles earlier, 82k on it now) they did a flush (fluid was clear though). has been fine the 300 miles since...

note: this was a very hot day and all highway driving through FL and GA....