Back to the tranny shop?

[Stripermike]

Hi all -
Any of you who followed my last thread regarding the bucking, hesitation in my 99 Tahoe will be glad to know - now that the issue has been resolved the truck is almost like brand new. Today I remedied another issue - the "clunk" in the driveline. I removed the driveshaft and applied some marine grade grease to the slip yoke, re-installed and was pleased to find that the "clunk" was gone.

My only "residual" issue now involves the truck "hunting" at about 45 - 50 mph. It seems to go in and out of torque converter lockup, "surging", I guess you could call it. I can watch the rpm's go from about 1000 to 1500 and then quickly drop back down - it will do this repeatedly with steady light pressure on the pedal, and I can feel the truck go in and out of lockup.

Anyone else ever have this happen? I once had a Honda Accord that did the same type of thing and it turned out to be just "the way it was" - I never experienced it in my 95 Tahoe though. Now that everything is running right should I address this at the transmission shop?

 

[Tex99Tahoe]

I'd take it back, and be upfront about everything you've found/done. Ungreased splines after an overhaul? What's goin' on out there???

 

[Stripermike]

I know, I know. I was surprised at no grease at all on the splines when I pulled it apart too. You know, my dad always said, "if you want something done right, plan on doing it yourself". Holds true more times than I wanted to believe, especially nowadays.

The "hunting" problem seems markedly better today though. I don't know if the computer needed a little time to figure out what the hell was going on, after all, it must have been more than a little confused with 6 of 8 fuel injectors sending fuel to the wrong cylinders.

I'm going to put a new set of plugs in for good measure, and go through and make sure all of the grounds are solid and clean. Otherwise I think it's time to move on to some of the "minor" little things I already planned on doing when I bought the truck - some front end parts, shocks, maybe even a hi-flow exhaust if I can squeeze it into the budget. If not there's always springtime....

 

[samotahoe]

I have the same problem with my Tahoe. but it normally happens more predominantly when the a/c is on and im cruising at light throttle, about 40mph. ive tested all kinds of stuff and I used a scanner with bi directional controls from snap on. ive even used a tech II to try and figure this out. but from all my investigating. im dubbing the trans as the issue. I haven't tried however to replace the tps, given the fact that its throttle by wire and its expensive so I figured Id live with it until I find more info on this. Please keep updates if you find something. that's really the last problem with my Tahoe.

 

[Stripermike]

Sam - what year Tahoe? I actually did replace tps on mine, looking for the cause of my other problem - wasn't too expensive actually.

I read a bunch of posts about this same issue all over the web. Some people chalked it up to "normal" operation of the trans, a few had luck changing out basic tune up parts, one post I read talked about making sure all of the ground wires were making a good clean contact.

I also read some stuff about debris in the valve body or problems with solenoids.

Scanners are great. But - I had 3 pairs of fuel injectors reversed, and no code for that. Needle in a haystack. Something I wouldn't have found on my own without a lot of help from this community.

I'll update on how things play out with the "hunting".

 

[samotahoe]

my hoe is 2000 (newer body style with the barn doors) 5.3L 2wd. the trans was rebuilt before I bought it cuz the shop has a stamp on it. after I bought it my rear diff spider gears literally blew up on me, so I replaced that. but ive done the tune up and cleaned throttle body. and what not but I still have that issue, only thing I can come up with would be the TCC lockup solenoid but the Tahoe is an extra vehicle that we use for the weekends and family trips, and towing. so its not really priority. but I would like to get to the bottom of it eventually and I will try my best to follow this thread. seems like you've been on a great learning exercise here lol. and as a mechanic, id say this is the best way to learn your way around your own truck with hands on experience. keep me posted

 

[Tex99Tahoe]

I recall long ago issues about lurch/hunt/lockup in the 40 mph zone. Factories issued recalls & tech bulletins, tranny shops implemented 'tricks' to widen the upshift/downshift/TCC decision range.

I wonder if your tranny shop implemented any of those 'tricks' to mitigate your previous problem.

I wonder if those 'tricks' need to be removed, now that the engine is straightened out...

 

[samotahoe]

TEX: if you can find the link, I have access to a tech II scanner, maybe I can recalibrate, it feels like I could adjust shift points if I could....