jmshawii
Newbie
1996 GMC Yukon 4-door, 4x4, 5.7, AT, 252K At least 1 and possibly 2 transmission replacements WAY BACK-I think there were a LOT of problems with these back in the day, no?
Speedometer not working correctly for years now-goes from 0-100 MPH very quickly upon starting to move and stays way high. I've read this is a small gear issue in the cluster itself. Regardless, has been this way for several years with no transmission issues.
Brake light switch stable and seems to be functional.
Cruise control worked at least sometimes up until fairly recently (6 months or so-4000 miles or so), but would occasionally spontaneously cut off. Now it seems not to work at all, though noticed this was not working completely separately from the transmission issues..
Shifts all feel normal for the most part. No hard shifting nor any really SLOW shifting in getting up to speeds. Starts off from stand still as well as it has for the last several years. Has been in the family since new and well cared for and well maintained all its life.
MAIN SYMPTOM is that it frequently will start "jumping" out of and back into OD when at 50-60 or so miles per hour. If I step on it and have it under "more load" the problem seems to go away or at least be less frequent. And I can sometimes get "underneath" it as well, by letting off of the accelerator and slowing a bit and it will seem to hold in what I guess is 3rd.
SOMETIMES it drives fine for fairly long periods/distances, but rarely. SOMETIMES it seems to jump between 2nd and 3rd a little bit as well when at lower speeds. SOMETIMES, even if I am manually in 3 and not in OD it still seems to want to jump around a bit.
I did late last summer/fall notice that I had some fluid cross-contamination with the radiator, which I think I caught very quickly and remedied. At that point I had not noticed any funny symptoms in the operation of the transmission. I had to use Bars Leaks kind of stuff in desperation at the time to close the leaks, and changed out the tranny fluid and filter and everything seemed fine for at least a couple thousand miles.
I first noticed the OD jump happening about 6 months ago (a month or two after fluid change and after driving those couple thousand miles) and it was MUCH less frequent/quite rare. But I definitely noticed it and began paying attention. Because of the reputation of these transmissions and the miles on it (I have receipt from the most recent transmission change and I'm pretty sure it had two, but haven't checked the mileage-I'm thinking this trans should have about 150k on it) and the former problems we had with the trans even when newer, I became worried I was going to need a new tranny. I did another fluid change/flush (through the lines-not removing the pan or filter this time) shortly after noticing this jumping around activity for the first time. I also tried to add a little bit of Lucas Trans-Fix, but it was SO thick I could hardly get any to drain out of the bottle and into the trans fluid tube!
It acted pretty good for some time, but occasionally would do this. I had to drive from GA to the UP of MI and it made it most of the way pretty well, but started acting up eventually and was doing this a lot more. I was pretty loaded down so started running just in 3rd and it did okay and got me there. Still didn't jump around TOO much after that, but would now and then. Then I had to drive to Toledo (450 miles), and, again, it actually did quite well and only jumped from OD-3rd a couple times the whole trip. A week later made the return trip with maybe a LITTLE more jumping, but still not bad. But after that, about 2 weeks ago, it has been MUCH more frequently jumping back and forth and occasionally jumping the lower gears, too, as I mentioned earlier.
So, because the shifts generally feel to me pretty normal-even when jumping back and forth they are very clear shifts-not "slippery" nor HARD shifts-and because it is not just 1+4 or 2+3, and because the fluid doesn't look or smell bad, level is good etc, and though at one point RIGHT after the big drive up from GA to MI it seemed that the trans was making QUITE a "whirring" sound ALL THE TIME-even when sitting still (I read somewhere on line about someone having blocked lines and wondered if the pump wasn't running a little dry due to some kind of blockage [back to that even thicker goo than normal LUCAS???] that finally freed itself or something) it really feels and acts normal in almost every way except for jumping back and forth between gears sometimes, so because all of that, it "feels" to me much more like an electrical kind of thing than a physical/mechanical thing. Yet it sounds like if it were selenoids, they affect the different gear pairs, and this seems to jump across all of those combinations. And if it were some other problems it seems there would be hard shifts or SOFT shifts or non-shifts! None of those seem to be a problem.
Thus, I have been looking at those possible causes, but none of the descriptions I've read on other threads really completely match mine (I've probably been through about 30 between this site and some others), so was looking for input here.
My main ideas right now are TPS and VSS and just wondering who has what input and why? And if there is a way to more conclusively test these to figure out if they might be bad. And if you think I'm totally off base, please let me know as well.
So, sorry for the long post, but TRYING to include as much detail as possible, because I know it gets sloppy when you have to keep answering all kinds of individual questions and your info ends up spread out over 7 pages of posts and no one can possibly get all the info.
Thanks for any help and advice! And thanks for being here.
Speedometer not working correctly for years now-goes from 0-100 MPH very quickly upon starting to move and stays way high. I've read this is a small gear issue in the cluster itself. Regardless, has been this way for several years with no transmission issues.
Brake light switch stable and seems to be functional.
Cruise control worked at least sometimes up until fairly recently (6 months or so-4000 miles or so), but would occasionally spontaneously cut off. Now it seems not to work at all, though noticed this was not working completely separately from the transmission issues..
Shifts all feel normal for the most part. No hard shifting nor any really SLOW shifting in getting up to speeds. Starts off from stand still as well as it has for the last several years. Has been in the family since new and well cared for and well maintained all its life.
MAIN SYMPTOM is that it frequently will start "jumping" out of and back into OD when at 50-60 or so miles per hour. If I step on it and have it under "more load" the problem seems to go away or at least be less frequent. And I can sometimes get "underneath" it as well, by letting off of the accelerator and slowing a bit and it will seem to hold in what I guess is 3rd.
SOMETIMES it drives fine for fairly long periods/distances, but rarely. SOMETIMES it seems to jump between 2nd and 3rd a little bit as well when at lower speeds. SOMETIMES, even if I am manually in 3 and not in OD it still seems to want to jump around a bit.
I did late last summer/fall notice that I had some fluid cross-contamination with the radiator, which I think I caught very quickly and remedied. At that point I had not noticed any funny symptoms in the operation of the transmission. I had to use Bars Leaks kind of stuff in desperation at the time to close the leaks, and changed out the tranny fluid and filter and everything seemed fine for at least a couple thousand miles.
I first noticed the OD jump happening about 6 months ago (a month or two after fluid change and after driving those couple thousand miles) and it was MUCH less frequent/quite rare. But I definitely noticed it and began paying attention. Because of the reputation of these transmissions and the miles on it (I have receipt from the most recent transmission change and I'm pretty sure it had two, but haven't checked the mileage-I'm thinking this trans should have about 150k on it) and the former problems we had with the trans even when newer, I became worried I was going to need a new tranny. I did another fluid change/flush (through the lines-not removing the pan or filter this time) shortly after noticing this jumping around activity for the first time. I also tried to add a little bit of Lucas Trans-Fix, but it was SO thick I could hardly get any to drain out of the bottle and into the trans fluid tube!
It acted pretty good for some time, but occasionally would do this. I had to drive from GA to the UP of MI and it made it most of the way pretty well, but started acting up eventually and was doing this a lot more. I was pretty loaded down so started running just in 3rd and it did okay and got me there. Still didn't jump around TOO much after that, but would now and then. Then I had to drive to Toledo (450 miles), and, again, it actually did quite well and only jumped from OD-3rd a couple times the whole trip. A week later made the return trip with maybe a LITTLE more jumping, but still not bad. But after that, about 2 weeks ago, it has been MUCH more frequently jumping back and forth and occasionally jumping the lower gears, too, as I mentioned earlier.
So, because the shifts generally feel to me pretty normal-even when jumping back and forth they are very clear shifts-not "slippery" nor HARD shifts-and because it is not just 1+4 or 2+3, and because the fluid doesn't look or smell bad, level is good etc, and though at one point RIGHT after the big drive up from GA to MI it seemed that the trans was making QUITE a "whirring" sound ALL THE TIME-even when sitting still (I read somewhere on line about someone having blocked lines and wondered if the pump wasn't running a little dry due to some kind of blockage [back to that even thicker goo than normal LUCAS???] that finally freed itself or something) it really feels and acts normal in almost every way except for jumping back and forth between gears sometimes, so because all of that, it "feels" to me much more like an electrical kind of thing than a physical/mechanical thing. Yet it sounds like if it were selenoids, they affect the different gear pairs, and this seems to jump across all of those combinations. And if it were some other problems it seems there would be hard shifts or SOFT shifts or non-shifts! None of those seem to be a problem.
Thus, I have been looking at those possible causes, but none of the descriptions I've read on other threads really completely match mine (I've probably been through about 30 between this site and some others), so was looking for input here.
My main ideas right now are TPS and VSS and just wondering who has what input and why? And if there is a way to more conclusively test these to figure out if they might be bad. And if you think I'm totally off base, please let me know as well.
So, sorry for the long post, but TRYING to include as much detail as possible, because I know it gets sloppy when you have to keep answering all kinds of individual questions and your info ends up spread out over 7 pages of posts and no one can possibly get all the info.
Thanks for any help and advice! And thanks for being here.