GMC Yukon '96 has MIL code P1870 for trans sliping

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Jim Spahr

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My friends 1996 GMC Yukon with 110k has a MIL code of P1870 displayed. This is displayed when the trans gets hot as in normal driving. The Yukon has a 4L60E auto trans and a 5.7L V8. The trans then has a very harsh 1-2 shift. The MIL TSB says the control Valve Body is worn and allows TTC slippage. Solution is to replace the Valve Body with a revised VB with the upgraded TCC regulator and isolator valve IF the ATF is not burned or the Torque Converter is not blue, as in overheated.
My questions are: is anyone familiar with this trans problem? Is it better to buy a new VB or a reman. VB? Is this something a good shadetree mechanic can do in the drive way , it he has the proper tools? Any tips? We'll assume the ATF is not 'burned'.
 
You might get lucky, I donno.

Every one we've encountered has had to either have a complete rebuild or a SRTA transmission.
 
If you catch it early the new valve body and a total flush will help you move on for about 30-45k miles before the next problem (fried bands and extreme slippage, converter, pump...etc.). The 1-2 bump shift as they call it is a common issue with the 4L60 E in those years. I got 45k more miles out of an S10 4L60E trans (operating behind a 300 horse motor) by snagging a new valve body off Ebay and stopping by a trans rebuilder for the remaining goodies (about $300 total spent on the VB and parts). About the only special tool that you are going to need (if I remember correctly) is a set of snap ring pliers for one of the accumulator valves and a magnet to fish out all of the little check balls. I'd say it's about a 4 hour job for the shadetree guy if you don't run into hick-ups. Just be careful to keep everything CLEAN! A few specs of dirt and you'll be grinding up that trans in a bad way! Good luck!
 
I here you about what GM wants to sell you, but if you go to ebay and type in "4l60 E valve body" you'll see what I'm talking about. Better yet here I'll put a link to one for you to check out. HERE.
 
The E bay site has a professionally reman. Valve Body esp. designed to address the Code P1870 in the 4L60E for $160.00 plus a 30.00 core charge. Good deal for a valve body. Nobody -Adv Auto, Auto Zone, or NAPA- carries the valve body. One source said to call a local auto trans parts supply company. They said when I mentioned code P1870 in a 4L60E: Oh, yeah, that's a common problem with those trans with high mileage. You don't need a new valve body, you need a Transgo shift kit with a bigger valve. I asked if it requires machining ( which I can't do) and he said oh, no machining required. The Transgo shift kit is only $54.24 and includes more than a bigger boost valve. It has 11 new springs and a valve and other parts. See http://www.transgo.co0m and part no. SK 4L60E. You would also need a new filter, gasket and ATF to refill and you are good to go.
http://transgo.com/4L60E-4L65E.html
 
Didn't know about that option...though I did mine a few years back. I do like the fact that the ebay guys stuff comes with all new solenoids and what not. I've done a few shift kits in other transmissions and you will still spend a couple of hours figuring it all out...it isn't hard to do though. I remember putting a B&M shift kit in a 1992 700R4 (basically a 4L60E without the fancy electronics) Corvette trans and that sucker hit the 1-2 shifts so hard afterwards I thought I was going to lose a universal!
 
My friend with the Yukon that inspired this research this morning has e mailed me he put his truck in the GMC dealership for the VB repairs today, that is, a reman. valve body as called for by the TSB. Estimate : $800.00. I then got the info on the Transgo shift kit repair and so didn't let him know about the $54.00 fix. I will let you know how his truck with the new VB drives and shifts. Transgo has fixes and upgrades for GM. Ford, Chrysler, Nissan and other trans.
 
Yeah I checked them out after your last post and it's a pretty sweet deal. Too bad your buddy has to drop $800!! A 6 pack, a couple curse words and some parts could have saved him some coin. Oh well let me know how smooth the 1-2 is with the reman VB.
 
There is a specific aftermarket remedy for this, which involves reaming out the valve body for a new valve. The reamer costs approximately $125, the valve costs relatively little. I suspect this is how the "remanufactured" VBs are done.

Sonnax TCC Regulator Valve Kits

Mr. C is correct though, from what I have read by the time the code generates, the converter is toast.
 
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I just got another e mail from my friend with GMC and remember he put the truck in the dealership Wed and now they say it will be ready on Friday. They estimate 11oo for a reman VB installed. They would have charged 2850.00 for a certified trans replacement. I am guessing a certified trans is a reman. trans under warranty. So it runs the gammut from 54.24 and DIY to 2850.00 for a reman.trans.
 
Dang...2850 gets me a lot of valve bodies and bone yard transmissions. I guess that piece of mind is worth a lot though if you are a one vehicle family.
 
Don't count your chickens before they hatch.
1100 bucks is a lot to spend on a 'fix' to a trans with 110K.
I hope it works out for your buddy but I would not be at all surprised if this TSB doesn't make it 100%
Lots of other internal problems can cause clutch slippage.
 
If this scenario takes a turn for the worse, he should ask them for a quote to install a new 4L65E, which is a 4L60E with upgrades on all the problematic hard parts. I priced one a couple of years ago and it came to around $2300 w/o installation - don't remember if it included the converter.
 
My friend got his Yukon back and paid $1,005. He says it seems to shift quicker with faster lockup. He will drive it from Dallas to Houston and that will be the real test.
 
My friend called while driving the Yukon in 6 lanes of traffic. The SUV made it to Houston and it is still shifting like a new trans. Yes, it gets hot in Houston and Dallas. I guess the TCC wasn't burned and so he gambled and made the right decision.
 
The GM reman. VB has an upgraded valve to correct the P1870 code. The Transgo shift kit says it will cure the P1870 code without machine work. I bought one of these kits, thinking I could install it. Well, it is way beyond my mechanical abilities. It requires dropping the VB and the separator plate. It does require drilling out some passages in the plate. Two drill bits are included.You need to have a vise or press to press one of the valves together. You have to grind notches into one of the cups. You have to remove the servo on the side of the trans to replace the valves and springs. $42 for the kit, but you need a new filter, pan gasket, and ATF, So it will be 52.00 plus ATF. Way beyond this shade tree mechanic. I know when to call in a trans expert.
 
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