What’s this transmission telling me?

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This is a 1997 GMC Yukon with a 5.7L and 4L60E with 168K. I bought in August from the original owner. I've drained and refilled fluid a couple of times and it looks pretty good. Based on what the seller told me, the vehicle has never towed more than a light pop-up camper. It had a service around 150K but otherwise had been left alone.

Overall, it shifts pretty well. But under anything besides light throttle, it can have a fairly rough shift in 1-2 and 2-3. I can make it shift perfectly smooth if I back off the gas pedal just before it shifts. It's also more noticeable up any sort of incline. And it's not big buck or jerk, but if you pay attention to such things, you definitely can feel it.

I have the same issue, though somewhat less pronounced, on a 2008 Suburban with the same transmission. A new throttle position sensor, shift solenoids and Lubegard didn't solve it in the Suburban and I've basically learned to modify my driving by feathering the throttle so it doesn't bug me as much.

I've researched the heck out of this but can't find anything that describes exactly what I'm dealing with. The fact that it does basically the same thing on two vehicles makes me wonder if it's just a characteristic of the 4L60E.
 
Big jump between 1&2, might be normal. Too new for a throttle valve cable that is out of adjustment? I wonder if the trans is running with high pressure or is thinking high(er) throttle is being used.
 
It never hurts to try a dose of Lubeguard red This is an exception to the rule about additives. This stuff works if the transmission is not too far gone for anything to work.

It will up the friction modifiers, clean varnish condition seals.

The trans may be too far gone, a "good" tech can read codes and advise you. Good is hard to find.

Rod
 
This is one instance where I would recommend a transmission fluid additive. There is one that is well spoken of...Lubeguard.
 
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Not sure. I haven't opened up the pan yet.

Thinking I might invest $25 in shift solenoids and possibly a bit more for some other internal bolt-ons and go ahead and open the pan up in the next few weeks. I've got a filter kit and drain plug on-hand already so I'd be killing a few birds in one stone. Everything inside the pan - outside the filter - should be original and is thus 23 years old. I don't love throwing parts at cars, but if I'm replacing 23 year old components, I don't lose a lot of sleep over it.
 
It's hard to know how severe it is over a text conversation, but every 4L60E/700r4 I've had has had what I would consider a harsh 1-2 shift. Can't say I've noticed the 2-3 was as bad but now I'm going to pay attention next time I drive my '98. I had one rebuilt (on a 96' Suburban) at 150,000 miles when it gave up the ghost and even after a rebuild it still shifted harder than I would have liked. Had the transmission shop work on it several times after the rebuild and I eventually decided it is what it is in that case.

I will echo other's statements about Lubegard red. It's good stuff and if it seems like the transmission is still functioning well, now is the time to use it (before it loses a clutch pack).
 
Thanks. I appreciate the Lubegard suggestions. I failed to mention that I have used it in the Yukon and didn't notice much if any difference.
 
Someone could have fiddled with the adjustment screw on EPC Solenoid, Used to be a very common mod! I say that because the 2-3 shift isn't normally firm at all & there isn't an Accumulator to effect it.....In the traditional sense anyway. 3rd gear oil pushes off the 2nd Band Apply piston therefore acting as a Accumulator.

Broken 2nd Accumulator springs are a very common issue, Especially on the earlier 4L60E's.

Installing a "Corvette" 2nd Servo without calibrating/sizing the apply orifices in the Separator Plate to match can also cause rough 1-2 shifts & will also affect the 2-3 shift to a lesser extent.
 
Originally Posted by RonRonnster
It's hard to know how severe it is over a text conversation, but every 4L60E/700r4 I've had has had what I would consider a harsh 1-2 shift. Can't say I've noticed the 2-3 was as bad but now I'm going to pay attention next time I drive my '98. I had one rebuilt (on a 96' Suburban) at 150,000 miles when it gave up the ghost and even after a rebuild it still shifted harder than I would have liked. Had the transmission shop work on it several times after the rebuild and I eventually decided it is what it is in that case.

I will echo other's statements about Lubegard red. It's good stuff and if it seems like the transmission is still functioning well, now is the time to use it (before it loses a clutch pack).


Because builders don't take the time to adjust the 2/4 Band clearance, A Transgo Shim isn't always enough either.
 
As another poster mentioned, the ratio step on these is large between first and second.
I'd say run it til it fails, and sleep well knowing this is one of the highest volume transmissions ever manufactured and reman units are cheap and quickly available.
 
Since it behaves normally aside from these slightly harder shifts, I also would just run it as-is. Keep up with regular maintenance and don't worry about it. I understand the feathering comment, I always try to back off slightly before the auto shift to soften the engagement a bit. Maybe not necessary, just an old habit from my 1972 Gremlin days... that thing shifted hard but never failed me once, in any way, over 100k miles.
 
Just to close the loop on this:

I threw a $21 NTK throttle position sensor on this truck last night and it made an immediate difference in the way it shifts. Much smoother.

The more I thought about what the transmission was doing and how I could get it to shift fine at a very specific throttle point made me think it was worth $21 to see if I could improve it. The one I pulled off was quite possibly the original, which might explain why it was misbehaving.
 
Originally Posted by HawkeyeScott
Just to close the loop on this:

I threw a $21 NTK throttle position sensor on this truck last night and it made an immediate difference in the way it shifts. Much smoother.

The more I thought about what the transmission was doing and how I could get it to shift fine at a very specific throttle point made me think it was worth $21 to see if I could improve it. The one I pulled off was quite possibly the original, which might explain why it was misbehaving.


So it appears the TPS voltage may have been out of calibration and or erratic, giving the computer bad data, which in turn made shift points and shift timing erratic.

Feedback like this helps all of us with future problems so thanks.
 
I had a similar TPS problem I'll share for the benefit of others. After having my tranny rebuilt several months following a head on collision, the tranny would start "slipping" while cruising between 60 - 70 mph. The shop redid the work and the problem remained. They acquired a different tranny, rebuilt it and the problem still remained. No codes were thrown. After this third rebuild failure, the shop owner drove around with me for nearly an hour, watching live data from a scan tool and probably making sure I was telling the truth.

$25 later for a new TPS and the "slipping" problem was solved. Very frustrating for everyone involved.
 
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