4L80E Not Shifting

[handcannon]

Pertinant Stats:
94 K2500 ECLB, F vin, 233K miles, new injectors and glows (Bosch Duratherms) less than 10K miles ago,

Problem #1
I have been noticing occasionally that the TC doesn't lock up. I have added manual TCC lockup. If I manually lock the TC it works right. Usually after a few miles it will eventually lock on it's own. Last Wednesday it never locked on it's own, even after 10-15 miles. It would lock though if I used the manual lock switch. The next day it locked as it should. I did notice only about 150 RPM change between lock and unlock. 1-2-3 & OD shifts seemed fine. From reading on here I am under the impression that the RPM spread should be more. Lockup clutch worn? Lockup solinoid sticking, getting weak?

Problem #2
This morning the cold start was harder than ever before. I don't think the glow plug relay was working. I have been suspicioning the relay to be getting weak as it doesn't always do much afterglow and frequently puts out a bit of white smoke until it warms up. I am planning a manual override eventually. I haven't worried much about this as it doesn't usually get very cold here. Anyway, a very hard start this morning and very smoky. Mostly white from cold motor but occasionally a black puff, until warmed up a bit. I'm giving this info because I don't know if it may or may not have any bearing on the real problem.

The real problem.
This morning after finally warming up it would only go in 1st gear, with occasional shifts to 2nd. I tried manually shifted 1st to 2nd to 3rd and back down. Sometimes it never went beyond 1st. At times it went to 2nd and downshifted manually to 1st. By this time I was close to being late so I just parked it. I've spent the last two hours searching and have found nothing that seems to be similar to my problems.

Outside of recent TC lockup questions I haven't noticed anything else unusual.

Due to previous commitments I may not have time to try doing any troubleshooting tomorrow.

I am not very well versed in auto trannies so what I am needing is some guidance for troubleshooting. I am not a novice at wrenching, although I'm not a pro either.

I am on a very limited income so I'm hoping to be able to get this running without taking it to a shop.

Thanks in advance for your help.

Don

 

[handcannon]

4L80E Not Shifting and Inconsistent TC Lockup

I started this thread in the tranny area and as expected it's going nowhere due to low traffic. Since this forum gets a lot of traffic I decided to put it here also. I need to figure out what's happened so I can start repairs.

The TC not locking until a few miles have passed has happened several times over the past few weeks but Wed is the first time it has never locked. Saturday is the first time I've noticed anything with shifting.

Anyway, here's what I started in the tranny section.


Pertinant Stats:
94 K2500 ECLB, F vin, 233K miles, new injectors and glows (Bosch Duratherms) less than 10K miles ago,

Problem #1
I have been noticing occasionally that the TC doesn't lock up. I have added manual TCC lockup. If I manually lock the TC it works right. Usually after a few miles it will eventually lock on it's own. Last Wednesday it never locked on it's own, even after 10-15 miles. It would lock though if I used the manual lock switch. The next day it locked as it should. I did notice only about 150 RPM change between lock and unlock. 1-2-3 & OD shifts seemed fine. From reading on here I am under the impression that the RPM spread should be more. Lockup clutch worn? Lockup solinoid sticking, getting weak?

Problem #2
This morning the cold start was harder than ever before. I don't think the glow plug relay was working. I have been suspicioning the relay to be getting weak as it doesn't always do much afterglow and frequently puts out a bit of white smoke until it warms up. I am planning a manual override eventually. I haven't worried much about this as it doesn't usually get very cold here. Anyway, a very hard start this morning and very smoky. Mostly white from cold motor but occasionally a black puff, until warmed up a bit. I'm giving this info because I don't know if it may or may not have any bearing on the real problem.

The real problem.
This morning after finally warming up it would only go in 1st gear, with occasional shifts to 2nd. I tried manually shifted 1st to 2nd to 3rd and back down. Sometimes it never went beyond 1st. At times it went to 2nd and downshifted manually to 1st. By this time I was close to being late so I just parked it. I've spent the last two hours searching and have found nothing that seems to be similar to my problems.

Outside of recent TC lockup questions I haven't noticed anything else unusual.

I am not very well versed in auto trannies so what I am needing is some guidance for troubleshooting. I am not a novice at wrenching, although I'm not a pro either.

I am on a very limited income so I'm hoping to be able to get this running without taking it to a shop.

Thanks in advance for your help.

Don

 

[ak diesel driver]

I would check out the CTS in the crossover as a possible TC issue

 

[NVW]

x2, it won't lock until 170 F from what I've read. A faulty sender will give incorrect info.

Somewhere on here there is a chart with the ohms for given temps.

 

[handcannon]

Thanks guys. Because of something I read on here somewhere I was wondering about the CTS. I've also been wondering if it could have anything to do with inconsistent glow plug relay operation. If anybody finds that chart please post a link for it.

I do have an update on the tranny. I've been home long enough to do some checking. A few days ago I was messing around with the manual TCC lockup switch and accidently blew a fuse. The TCC switch wasn't hooked up where my memory said it was so I started pulling fuses to find the blown one. There is a tranny fuse in the fuse block even though the manual that came with the truck doesn't show it. Tonight I pulled that fuse to check it. It was good but I'm guessing that it wasn't making a good connection as I drove the truck tonight and it shifted like it should.

Don

 

[ak diesel driver]

here ya go

 

[handcannon]

Update:

I got home with enough daylight to do some checking. The tranny shifted correctly tonight. Last week I was messing around with the manual TCC lockup switch and accidently crossed a wire and blew a fuse. The switch wasn't connected to the fuse that my memory said it was so I started pulling fuses to find the blown one. One of the fuses I pulled was the tranny fuse. I'm guessing when I put it back in it didn't make a good connection. I pulled it tonight to check it before driving and everything shifted as it should.

I still have questions about the TC though. When the TC locks up how many RPM's should it drop? If the CTS is not giving consistent readings will it cause the intermittent TC problems? Is there a way to test the CTS?

Don

 

[ak diesel driver]

check your other thread

 

[BoostN]

check your other thread

With that note, I've now merged these two threads together to lessen the confusion.

 

[bk95td]

You should have around a 500 rpm drop when it goes to lock-up.
I'm not saying yours is wore but something that does happen with the 4l80e's is the valve bore for the tcc[lock-up]wears out and the hydraulic pressure will leak and cause little or no lock-up. There is a kit called Sonax shure cure that you drill out the tcc bore and insert the sleeve and new o-rings. There also is a kit from sonax for the pressure control valve. Same thing happens there. This place sells the kits:http://www.bulkpart.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=2&Category_Code=4L80E

 

[handcannon]

Thanks for the reply Barry. I don't get into these other forums as often so I didn't see your reply right away.

I haven't done any checking on the CTS yet. Tax time and taking mom to PT twice a week now and working on mirror install has kept me busy. But because of the intermittent nature of the TCC lockup I am not convinced that the CTS is the problem area.

Your explanation of the TCC valve wear problem sounds very plausible to me. Rough bore making for inconsistent piston movement and causing inconsistent TCC lockup. Auto trannies are a new area for me and for this reason I'll do more researching and looking for pictures and diagrams on this TCC function.

On a side note/hijack of my thread. I have the mirrors mounted now and temporary power to the adjuster motors (haven't taken the dash apart yet to install the mirror wire harness). I still need to dig into the turn/running light wiring for hookup to the mirrors. Since I have the Suburban door window switches for front and rear window operation I've decided to go ahead and power the extra cab wing windows while I'm working on all the other wiring. So now I have most of the interior behind the front seats torn out and fabbing wing window motor mounts, as I have time. You will LOVE those mirrors. I can SEE behind me now, especially with the built in spot mirrors.

Don

 

[bk95td]

I've been intensely reading my service manuals for the big tranny troubles my 94 1ton srw is having. I only have low gear now. Dug out a parts tranny tonight.
I sat in my truck with the new mirrors after I mounted them. Yes they are great. More than day and night difference from the stock stainless ones.
It might help your tranny problem to disconnect the main connector[squeeze the front and rear sides like a childproof cap and pull out. It may have tranny fluid in it. Wash it out several times with brake cleaner,both sides.
Now that I have the 94 manuals I can scan any pages you might need for the tranny troubleshooting.