torque converter lockup problem...

[mark83161]

I am having a problem with my '83 K5 Jimmy. I bought it as a basket case, and have since had the 700R tranny, the 5.7L engine, carburetor, and most everything else either rebuilt or replaced. I am running 33-12.5 tires on 15 inch rims and 3.73 gearing.
The problem is that ever since the tranny rebuild the lockup malfunctions intermittently. It seems to work fine for a while (that is if it's working during this period, I'm not sure), then for several days it will "dump" (I say dumps because it feels as if the clutch is being released too soon and at too slow of a speed) into postition two immediatly after shifting into 3rd gear, only to slip out under the load. Once the truck shifts into 4th gear it again dumps into position two immediately, but refuses to disengage the lockup unless full throttle is applied, at which time it shifts back into 3rd gear. Then, just as it started, the problem seems to magically disappear for varying periods. I took the truck back to the Aamco dealer (who came highly recommended) and they connected an anylizer to my ECM and showed me that the ECM was commanding the shift into position two.
Has anyone else experienced this problem? If so, please tell me your solution.

Thanks,
Mark /forums/images/graemlins/1zhelp.gif

 

[YtseJam]

What do you mean "dump"? and if your transmission upshifts when you have Wide Open Throttle then you have major problems. When you have WOT condition throttle pressure should be high, either delaying an upshift or forcing a downshift, not an upshift. The converter clutch shouldn't engage until you have low tv pressure, high governer pressure, and are in high gear. So either you're wording what is happening wrong or you have some serious problems with the valve body.

 

[mark83161]

Thanks for your response. I misspoke.

I have revised my post to more accurately describe my problem. If you have any info as to why this is occuring, I would be most grateful. I have found a manual TC switch that I could install to override my ECM, but would prefer to get the thing running right.

 

[dyeager535]

Well, with your '83, I'm kind of surprised they could hook something up to it, there is no ALDL port AFAIK, maybe they hooked it up to the TCC plug at the tranny?

Anyways, your vintage truck, there are only a few inputs/conditions for TCC: VSS (vehicle speed sensor), Vacuum, (switch in the engine bay), and the brake pedal. Can't recall how, if at all, TV cable plays into TCC, but I'm thinking it doesn't.

The "ECM" on yours will control only lockup, and of course it could be faulty, but TCC is an unlock/lock proposition. Anything outside of that, is something else. You can unplug TCC at the tranny to test (for a short period of time, but as long as you want if its got a good aux. trans cooler) and see if all your problems are resolved. If they are, great, then you are golden.

Still having a problem determing what you mean by your post, but answer the questions, and we might be able to help you further. : )