1997 k1500 Chevrolet Suburban shaking/shuddering/jerking at highway speeds

[Fredje]

Hello fellow enthousiasts, recently my Suburban developed a jerking / shuddering when in lockup. I suspect the TC lockup, and after some research on the forums I indeed suspect the TC. The car has a little more than 130k miles. No codes are thrown.
Anything I could check myself? Any connectors / wirings? The fluid seems OK (clear), a little overfilled though. Thanks a lot!

 

[1998_K1500_Sub]

Hello fellow enthousiasts, recently my Suburban developed a jerking / shuddering when in lockup. I suspect the TC lockup, and after some research on the forums I indeed suspect the TC. The car has a little more than 130k miles. No codes are thrown.
Anything I could check myself? Any connectors / wirings? The fluid seems OK (clear), a little overfilled though. Thanks a lot!

If you keep a toe on the brake pedal, just lightly enough to close the brake switch, the TCC will remain unlocked.

If you do so, do the symptoms completely abate?

 

[Fredje]

Yes, disengaging the TC lockup through lightly touching the brake pedal solves the issue (when it is not in TC lockup).

 

[1998_K1500_Sub]

Yes, disengaging the TC lockup through lightly touching the brake pedal solves the issue (when it is not in TC lockup).

Let’s see if @NickTransmissions will respond.

 

[NickTransmissions]

Hello fellow enthousiasts, recently my Suburban developed a jerking / shuddering when in lockup. I suspect the TC lockup, and after some research on the forums I indeed suspect the TC. The car has a little more than 130k miles. No codes are thrown.
Anything I could check myself? Any connectors / wirings? The fluid seems OK (clear), a little overfilled though. Thanks a lot!

What you're experiencing is very likely to be the TCC slipping, however I'd confirm with a bidirectional scan tool...Plug it in, take for a test drive with live transmission and torque converter data displayed on the screen...Things you will be looking at are TCC slip speed and TCC Duty Cycle...When duty cycle is at or near max, slip speed should be 5RPM or less...If you observe slip speeds well in excess of that, esp during the shuddering episodes, then your TCC is slipping...Then the question becomes, why is it slipping...Causes usually include TCC regulator valve in the valve body (usually P1870 sets/stores, if so), leak in the TCC apply circuit either at the worm tracks between the spacer plate, valve body and case (unlikely), o-ring on the end of the input shaft (possible) or TC simply worn and failing due to old age (possible).

Let us know what the scan tool indicates and we can go from there.

 

[Fredje]

Ok thanks a lot! What bi-directional scan tool could I buy that is cost effective? I use a scan tool linked to my phone but did not see any codes or tcc related info. Thanks!

 

[NickTransmissions]

Ok thanks a lot! What bi-directional scan tool could I buy that is cost effective? I use a scan tool linked to my phone but did not see any codes or tcc related info. Thanks!

You're welcome, man. Check out Autel scan tools. Most will have everything you need and then some for around $500-$1,000 depending on specific model. Or you can go Snap On but they are alot more expensive...

 

[Fredje]

Tomorrow I'm going to call a repair shop who might have this sort of bi-directional scan tool. However I do not have any fault codes, is this strange? If the jerking would be caused by slippage, why would the P1870 not be flagged? Or: if there is no P1870, there is no slippage?
And now I'm thinking: once, not so long ago, but only once, I had the car stall when leaving my driveway. I never got to explain that, it never did it again, but I can imagine if the lockup engaged when getting slowly off my driveway it would stall the engine...
I did also change the brake switch because I experienced the cruise control switching off, and I experienced torque converter clutch disabling. That is cured now (except for the TCC issues I seem to have now), but could, theoretically, a malfunctioning brake switch disable the lockup briefly and then re-engage it?

 

[NickTransmissions]

Tomorrow I'm going to call a repair shop who might have this sort of bi-directional scan tool.

I'd suggest looking at the prices of various scan tools with bi-directional capabilities and then contacting the shop to find out how much a diagnosis will cost...My guess is that the prices for some of the more economical scan tools w/two-way and live data capability will be either roughly the same or perhaps only a bit more than what a shop is going to charge you to do something you can do yourself while adding a capability to your tools/skill set that you'll have forever vs depending on other people who are making money off you.

 

[Fredje]

So I went to the repair shop that has a lot of GM transmissions under repair and the owner did a 20min test drive together with me. He strongly suspects the converter lockup clutch. He will also check the solenoids/valves but the way it feels he said he was sure it was the clutch itself. It seems a very knowledgeable guy with good reviews, and only a 10 minute drive away from me. As I do not have the tools nor the experience I left my car with him and he’ll drop the gearbox asap and will give me a call as soon as it is opened up to show me. I will keep you posted even as I’m not doing it myself. Thanks for all the help!