torque converter lock-up

[blackhawk17]

I've put some of this info on a couple of older threads but have gotten no hits, so I thought I'd try with a new thread.

92 Z71 4L80e (I think). I've only had it for about a year and a half, and I just realized that since I've owned it when it upshifts into OD the TC has always locked up with the shift. So, when I tried to get on the interstate I'd end up gassing it so it wouldn't go into OD until I was nearly up to speed. Make sense? I just thought it shifted too early, but it occurred to me that the TC was actually locking.

Anyway, the TC has stopped locking now. I guess I'm kind of slow and now this is all coming together in my head. Yesterday it was VERY cold here in KS, and when the trans was still cold it locked in the lower gears, but once it got warmed up it wouldn't. There's been a couple of times I'd be at highway speed and tapped the brake with the left foot and it would lock up, but it doesn't usually work.

I know I need to change the fluid, so that's a given, so when it warms up a little I will. I'm just wondering if this is a simple solenoid/brake switch issue, or if I'm looking a a clutch- which would suck.

I am at about 220k, so I know I'm living on borrowed time as it is, but I need to stretch this baby out as long as I can. Other than this, the trans seems fine; no slips, grinds, anything.

 

[rhino]

Getting it on a scanner would be the easiest way to tell. You can watch the brake switch go on and off as you tap it. Second is watch to see if the TCC is being commanded on. If it is, watch the slip. Anything over 50 RPM is too much when it is being commanded on. 4L80E are bad about the converter clutch slipping. If it cost you $50 to get it diagnosed I think you would be money ahead rather than guessing. Good luck! Post the fix!

 

[great white]

On a 1992 Z71 I doubt you have a 4L80e.

80E's were on 454 trucks and diesels. It would be the first time I've heard of one on a SBC TBI truck (unless it's not stock). Your glove box should have "MT1" somewhere in the RPO codes if it is a 4L80E.

Likely the 4L60e. Maybe a 700R4. I can't remember what years they swapped over.

If it's a 700R4 your TV cable might not be adjusted correctly.

If it's the 4L60E it could be worn bores in the valve assembly, the converter clutch or several other things.

220,000 is no small amount on a 4L60E.

You can try and pull trouble codes, but I think they're fairly limited for transmission codes on OBDI trucks.....

 

[blackhawk17]

RPO code MD8- Transmission, auto 4 spd, THM 700 R4

So it's a 700R4. Thanks for the info.

 

[blackhawk17]

You know, I did just do a TBI rebuild a couple of weekends ago. I didn't notice the change until afterwards. It sounds like a may have screwed up the TV cable after all. I'll look into it. Thanks!

 

[great white]

You know, I did just do a TBI rebuild a couple of weekends ago. I didn't notice the change until afterwards. It sounds like a may have screwed up the TV cable after all. I'll look into it. Thanks!

Sounds like the first thing I would check....

 

[blackhawk17]

Well, it's not the TV cable. I'm not too transmission savvy, mainly because everyone I've ever known has been too afraid to mess with them. Therefore, I've never messed with them. So I looked up a lot of info trying to find an accurate description of how to set or "adjust" the TV cable properly on a 700r4 stock vehicle. I went through a lot of junk to finally find something useful, and my TV cable is set the way it's supposed to be. I thought it probably would be, but I wasn't sure considering that I unhooked everything to remove the TB. But that in and of itself should not mess with TV cable setting unless I was really being abusive under the hood- which I am typically very careful. Also, after reading about the role of the TV cable system to the trans (everything), I didn't think that was it considering none of my shifting or transmissin behavior has changed, except the TC doesn't lock.

This site has an excellent description of how the TV cable system operates and works for anyone looking for info- http://www.tvmadeez.com/article/index.php

 

[blackhawk17]

Update on TCC lockup problem. It had been so cold here i hadn't really tried to figure this out. But I've paid attention and I'm just about convinced it's just the brake switch. I can tap the brake a couple of times and it will usually cause it to lock up, so I guess tapping the brake resets it or something. So after I get that worked out I'll post the results.

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[blackhawk17]

Fixed the problem with a simple stop light switch. $13.99 at auto parts store. A super easy switch- took about 5 minutes with a screwdriver. Just for anyone else with the same issue, there is no adjustment for this switch- simply plug it in. At least for a '92. I can't vouch for all other years.

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