1997 Other GMC Models Transmission hard shift after engine g

HINESS

MEMBER
1997 GMC
V8
4WD
AUTOMATIC
16,000 MILES

My Suburban has run great until I started commuting. I've had a trouble keeping Antifreeze in the overflow 9so I'm sure the engine is getting extra warm but not overheating) When the engine gets warm after driving on the highway and I get off the highway, the first time I accelerate it gives a rough shift from 1st to second. (This continues on in the city) I've been checking the transmission fluid regularly and it is getting low. We had someone SUPPOSEDLY change the cooling lines and check it but he obviously didn't do what was needed. I really don't want to damage the vehicle by not doing what it needs. Any suggestions?

4 Replies

MASTERTECHTIM

MECHANIC
4,749 POSTS

The problem with losing coolant is most likely from the lower intake manifold gaskets(if they have not been updated yet) the transmission problem sounds like a stuck shift solenoid, there should be a code for this stored in the vehicles computer.**This will not illuminate the check engine light but will be stored. Autozone will scan the truck for free, get back to us with the codes.

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Wednesday, March 5th, 2008 AT 3:36 PM

2CARPRO JACK

MECHANIC
11,533 POSTS

Bunch of valve body updates for that trans as well, relating to harsh 1-2 shift

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Wednesday, March 5th, 2008 AT 6:37 PM

HINESS

MEMBER
2 POSTS

Hi Master Tech Tim,
I took the Suburban to the Auto Zone and they pulled the code - P1870-
Transmission is in 4th gear with TCC engaged and the ECM has detected excessive slippage whn comparing the input shaft speed with the output shaft speed.

I checked the fluid level last night and I'm wondering if I've got it full enough. It's really hard to see the hash marks on the dipstick. It appears that the "Hot engine Level" is almost 2-3 inches up from the bent part of the dipstick. Does that sound correct? Maybe I've kept the level WAY too low.

If it is the solenoid you mentioned, is this something my husband can do?
Thanks so much for the help!

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Thursday, March 6th, 2008 AT 12:13 PM

MASTERTECHTIM

MECHANIC
4,749 POSTS

I looked up the 1870 and there are several updates that a transmission shop can do to the valve body of transmission. My advice is to bring it to trans shop. They will not need to rebuild it, just update the valve body. Very common on these transmissions.

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Thursday, March 6th, 2008 AT 1:20 PM