NEED HELP Yukon Slipping Transmission

[$ Khalid ! 9130]

Well I guess I spoke too soon when I said both trucks were running perfectly!

We were on a trip outside the city about 400 KM in the Yukon. On the way back the transmission kept Slipping through gears and wasn't able to go above 60 KMPH on the highway. Eventually it started to heat up and Transmission Hot appeared on the DTC. We pulled over, let iit cool, and then towed it back to the city. Spoke to one of the mechanics at the dealership here and he said could be an issue with the sensors and the solenoid in the transmission if not something else and is a common issue on the 4L60 transmissions.

The truck has around 263000 KM on it with the original transmission, last transmission fluid change was around 70000 KM back. The transmission fluid was brownish in colour and smelt burned. The truck seemed to accelerate of the line in 1st quite well then spike between 2nd and 3rd at around 60 - 70 KMPH range with high revs

Should a simple transmission fluid change with the filter be attempted before dropping the trans, or something else you guys would recommend?

I'm just lost atthe moment any feedback would be really appreciated as always

 

[Mooseman]

would require the transmission be dropped to replace TCC sensor and Solenoid.

(From the "What did you do to your GMT today?" post.) Go to another shop. Your slipping shifts has nothing to do with the TCC at all. Could be a shift solenoid which all are serviceable with the valve body in place. However with the Km, the local temperatures it has to endure and the high temp DTC, it may just be done and need a rebuild. I would also look at adding even more extra tranny cooling for all your veicles. Check the tranny temps in your TB and if it goes above 200f (~90c), I would consider more cooling. Heat kills transmissions.

 

[$ Khalid ! 9130]

Thank you for the detailed information. If I'm getting at this right I should be able to change the shift solenoid by just removing the pan under the transmission?

The DTC message popped up on the way back on the highway. Didn't heat up today when I took it out.

So would it be better if I started with the shift solenoid and new transmission fluid and see if we get anywhere?

Thanks

 

[Mooseman]

Thank you for the detailed information. If I'm getting at this right I should be able to change the shift solenoid by just removing the pan under the transmission?

Yes

So would it be better if I started with the shift solenoid and new transmission fluid and see if we get anywhere?

Yes

However, if it's slipping at all shifts, it may be worse than just one solenoid.

 

[$ Khalid ! 9130]

Like I said it starts off fine but I'm guessing it's between 2nd and 3rd gear around 60KMPH. Might as well change all them while they're out?

 

[Mooseman]

Yep, might as well.

 

[$ Khalid ! 9130]

Just got the shift solenoids, transmission fluid, filter and the gasket done. Sadly it does seem like it will need a full rebuild. Third gear does not engage at all, seems like the clutch is gone. Will get to it on Tuesday most likely. Till then pics galore..

 

[$ Khalid ! 9130]

Have the transmission torn apart seems like the radiator lines caused water to get into the transmission causing the problem. A full rebuild is necessary and happening. One thing is like to ask is, is it absolutely necessary to use the special transmission grease when rebuilding? Seen it being used in some rebuild videos on the internet. Looks like blue or green grease. Or just soaking in transmission fluid with a little bit of Vaseline good enough?

Thanks

 

[cornchip]

I remember seeing a video online where transmission assembly lube was used sparingly. It's compatible with the internal parts namely the clutches. I wouldn't think Vaseline would be compatible. Wouldn't want to risk that new rebuild.

 

[$ Khalid ! 9130]

The issue is that no such lube exists over here, except for lithium grease. One thing I noticed when going through the interwebs was that the composition of Transgel is mostly petroleum based jelly

 

[gmcman]

I wish I saw this sooner. My 4l60E in the Envoy had a flare on the 2-3 shift around 170K....and wouldn't go away. Once I noticed this I took it easy for a few tanks of gas then tore into it.

What I noticed was one of the check balls was pounding it's way through the separator plate. I strongly recommend anyone dropping their pan, especially in the 150K range, to replace this plate with a dealer item.

At this time I also replaced both shift solenoids, I believe the 1-2 & 3-4 accumulator pistons, as well as installing the vette servo.

No aftermarket separator plate, no shift kit, just the OE pistons, solenoids, and separator plate. I used the trans-go vette servo.

If I did it again, I would also use the Sonnax super hold piston with the vette servo.

The possible bad....is the fact you drove it while likely slipping. Doesn't mean you smoked the trans, but if I was in the same boat as you, I would replace what I described and hope for the best.

One thing you have to pay attention to is the band, which is actuated by what's under the round cover housing the 2-4 servo along the passenger side of the trans. This is where the vette servo will go and increase holding power on the band. Once the band is gone, you need to pull the trans.

If you have a checkball that has pushed through the plate, you will bleed presssure as well as holding power on the clutches.

Will try to help as much as poss.

 

[$ Khalid ! 9130]

Thanks @gmcman for your input. Seems to be the case with mine as well, I've pictures which I'll put up soon, the balls have pounded thru the plate as you mentioned and the band is also done for. The friction rings have also sadly been burnt out. Seems it was a mixture of transmission fluid and water which also lead to the premature wear

I've got all the parts for the rebuild its just that i can't find the transmission assembly lube here anywhere. Closest I got was lithium grease. So right now I'd like to confirm if it's absolutely necessary, I've seen people rebuild with just a fab of Vaseline which I have plenty of 😅

 

[gmcman]

I would highly recommend getting with Dana at Pro Built automatics https://probuiltautomatics.com/

And see what he has to offer, let him know what you have.

I would also look into a new converter, Edge makes a great converter albeit a little pricey...but apparently worth it.

 

[$ Khalid ! 9130]

These are what I managed to click while I was staring at all this in awe!



Hopefully if the parts are in will be starting the rebuild today