'96 Yukon 4WD - 4L60E issues at 275K.

[DSinOR]

@NickTransmissions and everybody else...

I'm Dave, the original owner. I do all the service. It's a daily driver. The transmission is 100% factory.

Mountain life, 15 miles of curvy state highway, gentle grades, not on cruise control.
60mph in the straights, 35mph in the curves.
A few weeks ago, exiting a curve, gently accelerating back up to 60, I felt sharp "bucking" at 48mph.

It felt like something slipped for a fraction of a second and then instantly locked up again. About 8 times in 5 seconds, irregular, not rhythmic.
It wasn't loud. It was quiet, but you could feel each little shock. It only happened between 48 and 50, then smooth.

My wife and daughter drove it 400 miles the next day, mostly Interstate. It did it twice in 400 miles.
Their description: "brief lurching and washboard road sound," at about 50 or 55mph.

My best guess was TC shudder, so I added a bottle of LG Instant Shudder Fixx and everything was fine for 2 weeks.
Then my daughter said she felt the washboard thing again for a few seconds, so my mechanic friend in town hooked up a scan tool and went for a test drive.
No codes. He couldn't repeat the problem. He commanded TC lockup on and off and said the TC was working perfectly. He couldn't find any problem except the transmission fluid temperature reading was -38°. He said he thought the 3-4 shift might be a little slow, took a little too long to complete.

Big picture: I need to keep this thing running for a few months on a budget.

The atf has 20K miles on it, bright. I always did my own 3 gallon flushes by disconnecting cooling hose.
I put a 2nd magnet in the pan many years ago. The pan has always been clean, but I haven't dropped it in a while. Wix filter.

If I'm lucky, a new PSMA (temp sensor) might solve the problem for a little while.

This weekend, I will test the brake switch and wires, PCM wire, grounds, and fuel pressure. The plugs, wires, distributor, TPS and many other sensors are all new since last year. The throttle body was recently cleaned. Grounds are clean. I know engine issues can contribute to transmission issues, but I'm pretty sure I don't have any engine issues.

So I'm going to be ordering parts and dropping the pan.
What would you do while the pan was off?
Part of me is thinking new harness and solenoids, but another part of me is wondering if that is wise at 275K.
I've never done solenoids, but it looks easy and they are pretty cheap.

I found Nick's videos and posts. Thanks Nick!
I've never done anything to an automatic transmission, but I can, and help is available here. I have tools and decades of experience.
If this transmission dies this year, the most likely outcome is we will borrow a car from a friend while I drop it and rebuild it.

Today's goal: prolong the inevitable as long as possible. Get by.

What would you do while the pan is off? Do you have a preferred atf by the gallon?

Thanks!

PS - I already called the dealer in Wyoming where I bought it in 1996. I asked if they would tow it from Oregon to Wyoming for warranty repair. They said no, so I guess I'll have to get by on my own. I don't know what the world is coming to. You can't even get 30 years out of a car any more without having to fix something on it. SMH.

 

[NickTransmissions]

@NickTransmissions and everybody else...

I'm Dave, the original owner. I do all the service. It's a daily driver. The transmission is 100% factory.

Mountain life, 15 miles of curvy state highway, gentle grades, not on cruise control.
60mph in the straights, 35mph in the curves.
A few weeks ago, exiting a curve, gently accelerating back up to 60, I felt sharp "bucking" at 48mph.

It felt like something slipped for a fraction of a second and then instantly locked up again. About 8 times in 5 seconds, irregular, not rhythmic.
It wasn't loud. It was quiet, but you could feel each little shock. It only happened between 48 and 50, then smooth.

My wife and daughter drove it 400 miles the next day, mostly Interstate. It did it twice in 400 miles.
Their description: "brief lurching and washboard road sound," at about 50 or 55mph.

My best guess was TC shudder, so I added a bottle of LG Instant Shudder Fixx and everything was fine for 2 weeks.
Then my daughter said she felt the washboard thing again for a few seconds, so my mechanic friend in town hooked up a scan tool and went for a test drive.
No codes. He couldn't repeat the problem. He commanded TC lockup on and off and said the TC was working perfectly. He couldn't find any problem except the transmission fluid temperature reading was -38°. He said he thought the 3-4 shift might be a little slow, took a little too long to complete.

Big picture: I need to keep this thing running for a few months on a budget.

The atf has 20K miles on it, bright. I always did my own 3 gallon flushes by disconnecting cooling hose.
I put a 2nd magnet in the pan many years ago. The pan has always been clean, but I haven't dropped it in a while. Wix filter.

If I'm lucky, a new PSMA (temp sensor) might solve the problem for a little while.

This weekend, I will test the brake switch and wires, PCM wire, grounds, and fuel pressure. The plugs, wires, distributor, TPS and many other sensors are all new since last year. The throttle body was recently cleaned. Grounds are clean. I know engine issues can contribute to transmission issues, but I'm pretty sure I don't have any engine issues.

So I'm going to be ordering parts and dropping the pan.
What would you do while the pan was off?
Part of me is thinking new harness and solenoids, but another part of me is wondering if that is wise at 275K.
I've never done solenoids, but it looks easy and they are pretty cheap.

I found Nick's videos and posts. Thanks Nick!
I've never done anything to an automatic transmission, but I can, and help is available here. I have tools and decades of experience.
If this transmission dies this year, the most likely outcome is we will borrow a car from a friend while I drop it and rebuild it.

Today's goal: prolong the inevitable as long as possible. Get by.

What would you do while the pan is off? Do you have a preferred atf by the gallon?

Thanks!

PS - I already called the dealer in Wyoming where I bought it in 1996. I asked if they would tow it from Oregon to Wyoming for warranty repair. They said no, so I guess I'll have to get by on my own. I don't know what the world is coming to. You can't even get 30 years out of a car any more without having to fix something on it. SMH.

First, drop the pan and take note of what it looks like, the presence of burnt clutch material, metal, sand like debris that's either silver or bronze in color...If you see large amounts of any that, put the pan back on with a few bolts and yank it out for overhaul. At 275K you have done an excellent job of maintaining that transmission; it's like in the .001% percentile in terms of how long it has lasted.

That said, start planning for a rebuild or replacement...I'd not throw any solenoids, Pressure Switch manifold or anything like that unless you have a code specific to one or more of them or symptoms that match, which you don't per the above.

Your 3-4 pack is likely beginning to go out, along with the TCC so I wouldn't spend any more money on it in terms of new parts as it'd be like putting a clean shirt on a dirty body.

Any Dex-Merc certified ATF will do..I use stuff from Transtar since I get it so cheap but Valvoline, Castrol, Mobil, etc are all fine.

 

[DSinOR]

Update:

60 miles today, 50 hwy, 10 town. No shudder, totally normal, no codes.

Dash Command TFT went from 8° ambient to 82° C.
I guess my friend's scan tool isn't perfect with '96 OBD2.

I will check the brake switch and PCM-TCC wires just to be sure.

I was hoping to find some small things that might buy a little more time, like solenoids or harness, but I guess not?

If the PSMA isn't bad, I can't think of a good reason to drop the pan right now.

Basic questions:

1 - What do I need to buy? Which kit, TC, etc.

2 - Assuming drums and sunshell are still good, what's my ballpark job cost? Money's tight right now.

3 - I have a tranny jack. Harbor freight. Never used it. How high off the floor do the running boards need to be to clear the tranny?

4 - What's best? Drop it while it still works, or wait until it fails?

5 - Flush the cooler and lines, or buy new ones?

Thanks.

 

[GoToGuy]

Dropping the pan is part of the diagnosis, it gives you a visual/ physical idea of what could be going on inside. Not just the electronic self monitoring.

 

[DSinOR]

Also, BLK ground and BLK/YEL signal from PCM to TFT.

I'll check that. An intermittent short there would explain why TFT works today but didn't work yesterday when the shudder occurred.

I'm trying to get lucky here.

Open to ideas and suggestions. Thanks.

 

[DSinOR]

Dropping the pan is part of the diagnosis, it gives you a visual/ physical idea of what could be going on inside. Not just the electronic self monitoring.

"Dropping a pan is part of diagnosis." Thanks.

Car is fine 99.99% of the time. Everyone knows 275 is past due. Everyone knows my tranny is on the way out.

Options:
1 - do not drop pan, get lucky, find a broken wire, fix it, keep going.
2 - do not drop pan, keep going.
3 - drop pan, pan is clean, replace fresh fluid with fresh fluid, keep going.
4 - drop pan, pan is dirty, replace fresh fluid with fresh fluid, keep going.
5 - drop pan, pan is dirty, drop tranny.

Fluid is clean and bright on dipstick.
I'm not rebuilding the tranny this week or next week or next month unless I absolutely have to.
Thus, dropping pan does not change Options 1-4. See?

If you have a good reason to drop the pan, lemme know. I'm looking for a little luck right now.

Money's tight. Should be better in a few months. Say la vee.

 

[GoToGuy]

More accurate," Que Sera, Sera ".

 

[NickTransmissions]

"Dropping a pan is part of diagnosis." Thanks.

Car is fine 99.99% of the time. Everyone knows 275 is past due. Everyone knows my tranny is on the way out.

Options:
1 - do not drop pan, get lucky, find a broken wire, fix it, keep going.
2 - do not drop pan, keep going.
3 - drop pan, pan is clean, replace fresh fluid with fresh fluid, keep going.
4 - drop pan, pan is dirty, replace fresh fluid with fresh fluid, keep going.
5 - drop pan, pan is dirty, drop tranny.

Fluid is clean and bright on dipstick.
I'm not rebuilding the tranny this week or next week or next month unless I absolutely have to.
Thus, dropping pan does not change Options 1-4. See?

If you have a good reason to drop the pan, lemme know. I'm looking for a little luck right now.

Money's tight. Should be better in a few months. Say la vee.

You're overthinking this. Unless you have a compelling reason to drop the pan (ie you know for a fact one or more electronic components have failed), i'd leave it alone.

You know you're going to be overhauling the unit sooner rather than later so if it operates normally 99.99% of the time atm, leave it alone. When it finally craps the bed, remove and overhaul it.