97 Transport: Transmission (P1870) Problems

1997 Pontiac Transport with 185,000 miles.

A month or so back, I started getting a 2-3 second squeel that sounded like a slipping belt that eventually engaged at the end of the 2-3 second squeel. I noticed the power steering was dripping onto the Serpentine belt and dismissed the problem as a slipping belt. Then on a subsequent trip down to South Carolina, the Service Engine Soon (SES) light appeared and the tranmission would no longer lock up the torque converter.

Autozone found two (2) error codes, both of which were P1870.

After surfing the web last night I found a bunch of info on the P1870 that had to do with slipping Torque Converter Clutch (TCC) problems. Most of the posts had to do with Chevy Trucks, not minivans. It appears that GM replaced cast iron their valve body with Aluminum and suffered loss of wear resistance. Apparently the valve gets worn and fails to generate proper pressure to the TCC, and causes it to slip. Last evening I pulled the PowerTrain Control Module (PCM) fuse in effort to clear the code. This didn't work, but this morning I once again experienced the 2-3 second squeel as the TCC tried to engage.

I have called the Transmission shop and they are quoting prices from $800 to $2000. I am about ready to sell the minivan for $2000-2500; hence, this sort of investment seems foolish.

Questions:
1) Is the TCC probably toast?
2) If I replace the Torque converter ($119 at Autozone) will I also be replacing the TCC?
3) How much of an effort is it to replace the torque converter on a 97 transport? Do I have to remove the tranny onto a bench?
4) For the valve body, I see there are several companies that make a "Bore & Sleeve Kit." Anyone have experience with this kit? What special tools are required? How much of an effort to get the valve body out so it can be bored and resleeved?
5) Is there any wisdom in rebuilding the valve body first and then replacing the torque converter only if the problem persists? (Does it make far more sense to replace both while I'm elbow deep in the tranny? (remember, I am going to resell this soon and I want to be honest as to what I have repaired)

Thanks in advance.
Justin Koch

Bump!

I'd love to see some responses to your questions. I have a torque converter on a 1997 Trans Sport that doesn't seem to unlock very well. Going up a slight hill or undergoing moderate acceleration at freeway speeds, it starts to shudder/shake until the the torque converter unlocks, which it does with increased acceleration pressure. The shake has possibly gotten worse recently, though we first noticed the problem a couple years ago. I'd love to know how likely a new torque converter might be to fix my problem, and how difficult they are to install.

I'd love to know too.

Problem fixed, at least for my code P1870

Last week I was traveling from LA to El Paso TX, and the service engine turn on and I stop at Autozone and the P1870 appear two times.

As usual the delear transmission mechanic said that I need to replace the transmission.

I read a Haynes manual that I bought at AUTOZONE and the manual said that if the transmission mudulator was failing the vehicle will exhibit problems such sliping (CODE P1870) or shifts that are either too soft or too harsh.

After cheking there was no vacuum problems I bought the transmission mudulator (120 dlls), the transmission valve (5 dlls) and O ring (5 dlls) at the dealer, the modulator that I remove did not have any oil or vacuum leaks but it was requesting more than 20 inches of vacuum to do the job, so I replace the parts that I mentioned before and the light turn off and the transmission is working fine.

I think that due to the constant heat and the high millage (105000 miles) the modulator diafragm was not flexible any more so it was requiring more vacuum inches, I compare the new one ant the old one by sucking air with my mouth it it was a lot of diference.

Well the procedure to replace this parts is very easy, it will take no more than 30 or 40 minutes and it is described on the haynes manual

I hope this help you.

Thanks for the post. My 98 came up with the same error last weekend on the way down to the Indy 500. It was hot, but probably not as hot as you had it. Question though, what did the part look like that you replaced? Was it this (http://www.partsamerica.com/product_images/AAP/SAG/MD-28.jpg)? The GM parts diagram on GMPartsDirect make it appear like this is all that you replaced. But if it is, you really over paid at $120. After market the modulator runs $20.

Most likely problem is related to the valve body,,,and one of two valves....One is a direct replacement,,,the other requires reaming....the other problem is to replace them is very labor intense,,,a fair amount of skill is required ,,,,,most trans shops won't offer to repair because of warranty issues........What happens is the valves are "stroking" in the vb quite a bit,,,,YES they are not "hardened" enough and see side-load pressures which causes them to wear and then "stick"....The aftermarket valves have been re-engineered to address this problem,,,and work well...Synthetic additives like Lub-Guard,,,or a blend of synthetic ATF,, sometimes will ease the sticking.....SAD because trannys are scrapped for this problem!! Good luck

It is a metal cylinder 2" diameter that is located below the air filter hose, you need to remove this one to access the modulator, the vacuum hose is metallic and goes from the upper front part of the intake to the modulator, you can not missed but if you buy a 15 dlls HAYNES manual you will be able to se the procedure to replace this part and all the necessary pictures.

When I request this part on the dealer parts desk, the guy told that the transmission did not have a vacuum modulator, so I ask him to put the transmission lay out on the screen to pinpoint the modulator and valve and that is how I was able to order the parts

I hope this info can clear your doubts

Yup. That's exactly what I thought it was. The dealer really takes you to the cleaners if they do charge $120 for it.

i had this same prob. mechanic said $1400 to fix it (change torque convertor, etc.) or $3200 to rebuild and re and re. Not having that change laying around, i searched around. I found your post. I got out the trusty Hanes and set to it. 45 minutes later took a test drive at city and freeway speeds. All shifting fine, no slipping or rough shifting from 3rd to Overdrive or back! $43 for the parts and it works! Thanks!!

I have the Haynes book and cannot find any pictures or words about the modulator. Page numbers?

(Concerning the 4T60E trans. vacuum modulator)
>"It is a metal cylinder 2" diameter that is located below the air filter hose, you need to remove this one to access the modulator, the vacuum hose is metallic and goes from the upper front part of the intake to the modulator, you can not missed but if you buy a 15 dlls HAYNES manual you will be able to se the procedure to replace this part and all the necessary pictures."<

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