4l60e stator bushings and p1870 slip code

MAKE: Chevy
MODEL: S-10 Blazer
YEAR: 1999
MILES: 140k
: 4.3

I have a p1870 transmission torque converter slip code. Poor mpg. Bluetooth scanner with Torque app shows 150+ TCC slip on level ground and steady mph. Also a slight amount of fluid leaks from small tranny vent tube while driving. Fluid temp at 205 degrees after 30 minutes of driving. Tranny Fluid pressures 80 psi at idle, and about 120 psi on highway.

Dropped tranny pan. Fluid red. No debris. Discovered previous owner had already tried Transgo shift kit with TCC regulator/isolator fix. I thought it might be severe bore wear, so I installed a new valve body with reamed bore and Sonnax regulator/isolator sleeve and valves. Cleared code, but still no joy, P1870 and slip continues.

To avoid tranny drop I tried one last ditch effort. Checked TCC apply valve for 1/2" of travel. Checked fine. I removed TCC apply solenoid, removed its screen, and put a check ball in its snout. Should have made engine stall in drive while stationary (brakes applied) as converter would be locked. No stall or stumble.

So I dropped tranny. Converter looks brand new. No burn marks, perfect paint. Clutch packs not burnt. Drum where band rides still has scotch brite marks where someone removed any glazing. This tranny appears to have been recently rebuilt. I purchased the blazer a few months ago.

The only potential problems I see are rear stator bushing wear and input/turbine shaft wear. See photos. The rear stator bushing is worn to the point where one of the oil grooves is completely gone. 180 degrees from that wear, the bushing has not even touched the shaft journal. Photos show bushing at worn spot and unworn spot. The turbine shaft where it inserts into the torque converter is dished and wore a fair bit. O-ring was ok or at least not flat. I removed the o-ring for the photo.

My question is if this kind of wear can cause TCC slip? Is this my smoking gun? I plan to replace turbine shaft and stator bushing.

check for the check ball in the input drum also check the seal on the input shaft. Where did you get the valve body from was it a good company
Thanks for the input. The valve body was from an ebay seller. But it was definitely reamed and has a Sonnax valve installed in the reamed regulator bore. New solenoids. I suppose the AFL bore could be wore but surely not on both the old and new body both.

Do u mean the check ball in the end of the input shaft? It's present, suppose I should make sure it seals. But I'm gonna replace the entire drum and input/turbine shaft anyway.

As for my original question, could the rear stator bushing and input shaft pilot journal wear alone cause the slip?
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No, only the TCC Isolator & Regulator Valve Kit, as well as accumulator pistons.

I had just figured since someone before me tried the whole Transgo kit, then I tried a different valve body with Sonnax regulator/bore, it was unlikely to be VB.
I'm getting the sense that you don't think the rear stator bushing wear is bad enough to cause the problem...and that it may still be the valve body...
Could the line pressure results posted in my OP give us a clue about the problem being in the pump vs the valve body? 80 psi idle/120 psi cruising at 2000 rpm.


Staff member
I'm not savvy enough on that (or any other) auto transmissions to even have an opinion on that bushing wear. As to the pressure, there is probably a "quickie" test for that, but I don't know the particulars. On a Saturn S-series TAAT you should have about 60 psi idling in P, then when you pull the line-pressure fuse the line-pressure should rise quickly to the max (about 260 psi), indicating that the pump can provide proper pressure. that test kind of eliminates the pump as a problem, hopefully the 4L60E has a similar kind of pressure test and somebody else can provide the particulars. Note that you will still have no real handle on the PWM control of LP, for that you will need a factory-type test setup.
ok the bushing is a issue but not for the lock up problem that is a valve problem i use central valve body for my reman valve bodys they do all sonax upgrade not just 1


Hero Member
I'm going to add this because before bp came onto the scene, we had another transmission guru here that had some insight into this. Search this site for P1870 back in the 2007ish era for more info.

Having said that, I'll leave you with this, and the fact that with your current mileage, a complete overhaul might not be out of the question.

I should do a "canned reply" to this question. You are not the only one with this problem and for some reason all the techs and general media blames the valve body. The problem as I have found it leads right to the stator bushing in the pump, the rear one to be exact and the fix is simple (if the trans is out). Replace this bushing with the new and improved one from the kit and viola, problem and code gone. The valve body replacement will put the light out in some cases but not because this is the problem, it just seals some of the inherent leaks in the system. The major leak at the pump stator will wear the valve body out as well as the pump itself. Hope this helps, Transman
I installed a new bushing and new turbine shaft/input drum. The P1870 code is gone and TCC slip is back to acceptable levels at lockup. Appears that the bushings are vital to allowing the teflon rings to seal on the turbine shaft.

It was a long journey and I learned a lot. It would have been simpler to just pop a new tranny in and drive on. But I'm glad I stuck with it and learned.

Thanks for all the input. Hope this helps someone else down the road.

Remember that if the Transgo or Sonnax band aids don't fix your P1870 code, the problem is deeper. In fact, if you have the code, you probably are on borrowed time , even if the bandaid valves make your code disappear. Transman seems to know what he's talking about.
I did like billr did and just ignored it. Read on to find out what can go wrong with ignoring a P1870

97 K1500 suburban I did a rebuild six years ago. The 3-4 clutch packs burned out and we ignored it for about 2 years, just drove in 1st and 2nd.

I put in a Transgo HD2, beast sunshell, 5 gear planetaries, new reverse drum and replaced all the standard stuff(seals, bands and frictions).
I got it all back together and it worked great. Only problem was it still had a P1870 code. I was annoyed but didn't have time to deal with it.

Fast forward 6 years and the pump rotors died. They were in multiple pieces and looked like they exploded. (I got a sinking feeling when I found pump vanes in the neck of the trans filter)

My best guess at this point is that given the wear on the tangs, the torque converter wasn't seated completely(2/3 of the way). Add the high line pressure because of the P1870 code and I can see why the rotors gave out.

So I have to figure out what is causing the P1870 code. I remember having trouble getting one of the pump bushings out and may have just left it in. I'll check that tonight. I know the front bushing is thrashed.