A friend at work has a 1999 GMC Jimmy with the 4.3 TBI, and 94,535 miles on the clock. He was asking me about a trans problem he is having, only once the truck gets warm after it's been driven a while. He was describing it as "slamming" when it shifts into second, and mentioned how the check engine light will also come on. Says that if he just does short drives close to home it's fine. I checked the fluid and it's full and halfway decent looking, doesn't look great, but it's not brown and doesn't smell burnt. So I hooked my scan tool up for him and pulled a P1870 - "Trans Component Slipping" code, and told him that I'd ask my buds on PT.net to see if there's anything easy or common, or if this is the beginning of the end for his 60E.

Any thoughts?

 

Very very common on older 4L60's. The converter isn't applying all the way, there for setting the P1870 code. Once the code sets, the PCM will command maximum line pressure. Thus causing the harsh shifts he is describing.

Eliminating the PWM control of the converter majority of the time fixes this issue. Search around for 1870 valve. Sonnax and a bunch of other companies sell valves for this issue.

 

Very cool man, thanks!

 

Bulletin #01-07-30-023B is for replacing the valve body. I know the sonnax valve requires a special bore to install the new valve. The bore is like $180.

 

To me it seems like if you run one until you get the P1870 transmission death detected code you are on thin ice. It may live and it may have smoked it depending on how long people deal with the hard shifting before they think its bad enough to have it looked at. When I got my 99 right away I noticed the converter was not staying locked. It would lock for a few seconds then unlock and did this continuously. I put a transgo HD2 shift kit in it and killed a flock of birds in that one stone. As said there are other more economical options to addressing the issue.

 

I found the Sonnax valve and tool via a google search...the reamer tool is more expensive than the valve lol, just about double at $45ish for the valve and $87ish for the tool. There are also a few options on ebay, one of which is a reman valve body for like $115. Guess that I'll talk to my buddy on Monday and give him a few options...curious how much I should charge to swap out the valve body if I go that route...

 

It's good to see the price of the reamer has come down. With a skid plate labor is around 1.9 hours.

 

All the transgo kit does it send a different style valve and a spring and it shoves the valve all the way over so the passage stays open all the time making it a simple off/on circuit with no PWM control. There is no reason to ream anything or do anything different unless you are wanting to keep the PWM BS functional and I have no idea why anyone would ever want that. Doesn't the transgo SK jr. kit have the PWM delete valve in it as well? Worst case scenario you may actually FEEL the converter lock.

 

What's PWM, Pulse Width Modulation? I remember Justin mentioning something about it when he was in Jersey and we were updating my tune and he felt how hard my tcc hits. I found some inexpensive valve/kits on ebay...anybody have any experience with these?

http://cgi.ebay.com/ebaymotors/Code-...Q5fAccessories

http://cgi.ebay.com/ebaymotors/4L60E...Q5fAccessories

 

Yes it stands for pulse width modulation.

With the shift kit due to the PWM delete the TCC lockup feels about like a stock up shift does. Its noticable, not hard, I wouldn't even call it firm, but positive. The 93-94 4L60Es had no PWM at all it was a simple on/off circuit as it should be and they never gave any issues that I'm aware of. I'm curious if the PWM solenoid could be manipulated via tuning to take the place of actually changing the valve out to disable it. Could be the lazy mans fix until he gets his ambition built up to actually fix it.

I don't care what they say PWM started in 95 on the 4L60E. The ones that have it have PWM cast into the pump housing which mine clearly did as well as having the circuit in the connector for it as well as setting a code for the PWM solenoid which I had to turn off with tunerpro after I put the 4L80E in.