Hot tranny shifts hard!!!! HELP???

[JetSnake]

I have a 99 S-10 pick-up with a 4L60E automatic transmission. Every time I drive on a warmer day with the A/C on for about a half an hour, the transmission starts to shift very hard. Mostly form first to second. It's so hard that is chirps the tires.

I put on a external transmission cooler with very little help.

What would cause this and how do I fix the problem?

 

[HardbodyLoyalist]

When the was the fluid/filter last changed?

And with what?

 

[JetSnake]

A fresh change of Amsoil ATF and filter where of no help.

 

[eljefino]

Could be something like a line pressure solenoid getting weak. The default is firm shifts. These are usually in the valve body and don't require completely dismantling the trans.

 

[Jim Spahr]

You should have a MIL /CES lamp showing you have a code stored in the PCM-computer. The PCM controlls both the engine and trans. The code should be something like P1870, IOW, one alpha and 4 digits. Find out what the code indicates and post that. The trans is going into a 'default' or limp home mode. You may have no 4th gear ( OD) as well as a harsh 1-2 shift.

 

[dickwells]

These things seem to get wear in a part that causes this, and I cannot remember which part but Sonnax or sonnex makes a repacement for the piston and cylinder, maybe it is an accumulator or some such.

 

[JetSnake]

I still have forth gear but when the check engine light comes on I don't think it "locks-up". The RPM goes up about 200 at 60MPH when the light is on. The light is not on now and the code is cleared. But when I checked it in the past I thought it said something about a slip. I'm not sure. I'll try to scan the codes again to see if it's there.

I have a more serious problem. I'll post that on the same forum page.

 

[Jim Spahr]

A common problem with the GM 4L60-E trans is the code P1870 which is 'Transmission component slipping.' The PCM is comparing the engine RPM to the trans output signal. This may be the TCC slipping or other internal trans slippage. Usually slippage only when hot implies a hydralic leakage in one of the valves in the valve body due to wear. Sonnax does sell kits such as TCC regulator valves which are oversized and you have to drill out the valve body to install. I would take it to a reputable trans shop and ask them to change out the fluid and filter. Complete flush if you can afford it. Sometimes the fresh thicker ATF will increase the line pressure to reduce slippage and stop the code from setting.

 

[JetSnake]

I just had the code scanned and P1870 is what came up.

Can I install one of these sonnax kits myself?

 

[Jim Spahr]

First try changing the fluid and filter at a reputable trans repair shop. They can look at the residue in the bottom of the pan and tell you what is going on with your trans. Like I said above, the fresh fluid may help. Can you install the Sonnax kit? That's hard to answer. The skill to ream out an aluminum valve body without ruining it would be the test. If the trans flush doesn't help, price the cost of a new valve body.

 

[JetSnake]

I talked to a guy at sonnax and told him my problem. He said my TCC valve is shot and need to install this steal sleeve to fix the problem. The problem I'm having now is that the kit to fix this is $45 but the reamer used to install the steal sleeve is $130.

I guess I'm still better off then if I bring it into a shop.

Even on their web site shows a kit that is made just for my problem.

I take it the TCC valve is in the valve body and not the case?

 

[unDummy]

Since this occurs because of HEAT, install the biggest ATF cooler that you can find. What size cooler did you install? pre or post factory cooling?
Monitoring an ATF temp gauge to see what temp the problem occurs at and keeping the ATF below that might be cheaper than a new VB.

Am$oil was the wrong ATF to use when using fluid to debug a mechanical problem.

ATF thins at temperature and the thin ATF is more likely to blow-by the tired and worn VB. A thicker ATF might be a better choice. Pennzoil/QS high(er) mileage ATF is one the thickest at 8.5 cst. Most ATFs are in the ~7ish range. Old sheared fluid could be as low a ~5-6.

Or, try a bottle of transmission snot.

The Sonnax kit, along with the required tools, can cost as much as the VB. Buy the rebuilt VB from your dealer(or online store).

How many miles on that transmission? and maintenance history?

What you need to consider is the cost/benefit of the VB vs the cost of the new transmission when it fails.
Either drive it as is until the tranny falls out, or fix it now and hope that it will last a few years.
IMO, if it has over 150k miles, its a good core for rebuilding(wait 'til it fails). If it has under 80k, I'd fix/replace the VB now.

 

[JetSnake]

Thanks for the input.

When I put in the Amsoil, I didn't know I had a mechanical problem. At the time my dex-cool turned to mud and was covering the cooler in the radiator. To be honest I thought that was my problem from the tranny over heating.

I installed a cooler after the factory one. I think it's about 15" by 8".

I can buy the sonnax TCC kit and reamer for about $180. What is the average cost of a VB?

Now that I know What the problem is, I want to fix this as soon as possible before I have to replace or rebuild the tranny. I'm just trying to decide which route to take.

That tranny has 167,000 miles on it.

The sonnax guy told me to look at the torque converter, if it's not blued from heat then I should be OK with a TCC valve fix.

 

[Jim Spahr]

Jetsnake, I am confused about your previous radiator cooler problem. When it broke, did the Dexcool coolant mix with the ATF? I am wondering if your trans fluid filled up with coolant? As to your earlier question re: can YOU install the Sonnax kit? I would say no for 2 reasons. 1./ you not only have to remove the Valve Body-VB- you have to precisely drill it out. I would leave that to a trans pro who has done it before. 2./ The cost of the reamers is too high to use one time and put in a drawer. Sonnax generally sells to the trans rebuilders, not to the car owners. I do think you could install an new or rebuilt VB yourself. And I agree with the Amsoil ATF as being too thin and a thicker petroliem version would be better to boost line pressure. I know you dont want to hear that because the Amsoil is expensive.

 

[JetSnake]

The radiator cooler didn't brake or mix fluid. When the Dex-cool turned to mud, it was built up on the coolant side of the cooler. I felt this was hindering the cooling ability if the cooler.

I have an aircraft mechanics license. Taking another valve body off is not a problem for me.

Spending $130 on a reamer that I might only use once doesn't sound like a good plan to me. But look at it this way. If I take it in to someone else, it's going to cost me a lot more then $180 for what it would cost to do myself and I trust my work more then a repair stations work.

About the Amsoil, that's not a problem. It's been it there for a while and should come out anyway. I've had this problem for about 70,000 miles.

I don't want to cover up a mechanical problem by using a thicker oil.

 

[Matt_S]

GM has a service bulletin about your condition that seems to confirm what you've been told. The bore in the valve body that contains the TCC (Torque Converter Clutch) isolator and regulator valves wears, causing these valves to stick. As a result, the TCC does not apply and you see higher rpm at speeds where the converter should be locked up. The computer will detect the torque converter slippage and will set a code and apply full line pressure to try to protect the transmission. The high pressure is what causes the harsh shifting. The bulletin mentions that the trans typically has to be at an operating temperature of 200F or higher to replicate the problem.

That kit should fix the problem if it addresses the wear problem in the valve body. GM's recommended solution is to replace the valve body with an updated part available at the dealer. You might want to investigate that option. Pricewise, it will probably be comparable to the kit if you do the work yourself.

 

[obbop]

"GM's recommended solution is to replace the valve body with an updated part available at the dealer. You might want to investigate that option. Pricewise, it will probably be comparable to the kit if you do the work yourself."

Has GM started installing the improved component at the factory or do they use the old style still to continue their "cash cow" as folks bring their sub-par tranny in for repair?

Curious 2004 4L60-E owner wants to know.

 

[JetSnake]

Yup, sounds like were all on the same page.

I called two dealers and they both want almost $500 for a new updated VB. Neither one of them could tell me what the difference is with the updated one.

The more I think about it, the more I think I will buy the sonnax kit and reamer. I think.

 

[obbop]

quote:

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Originally posted by Matt_S:
obbop, I believe the manual stated they starting using the updated part in model year 2000 vehicles from the factory. It should certainly be updated in your '04 already.

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Thanks for the info. Sure hope the tranny lasts awhile. All precautions taken and I treat the truck better than that woman who crawls into my bed with those cold feet.

 

[Matt_S]

obbop, I believe the manual stated they starting using the updated part in model year 2000 vehicles from the factory. It should certainly be updated in your '04 already.