Suburban 4L60 problems

[1of1547]

I know it's not a Buick, but I need some help on our Suburban. It is a 1999 with a 350 and 120,000 miles on it. Every now and then it will shift very hard. It actually feels like a manual valve body shift. It normally does it after we have went for a 30 minute trip or so. Is there a valve or solenoid that is going bad? Or does it just need a rebuild? What is the average life for one of a 4L60?

 

[gsgns4me]

It is probably setting a DTC P1870, which doesn't turn the CEL on, but causes the trans to go to full line pressure and you get the harsh shift. This DTC is for excessive slippage. This is a misleading title for the DTC. It can be caused by a worn tcc valve/valve bore not allowing full apply pressure on the TCC and the computer interpets it as slippage. It can also be caused because the trans is worn out/burnt. Inspecting the filter and pan may help determine how severe a problem you have.

There are kits available from the aftermarket to repair the valve body. GM's answer was to replace the valve body.

 

[1of1547]

It is probably setting a DTC P1870, which doesn't turn the CEL on, but causes the trans to go to full line pressure and you get the harsh shift. This DTC is for excessive slippage. This is a misleading title for the DTC. It can be caused by a worn tcc valve/valve bore not allowing full apply pressure on the TCC and the computer interpets it as slippage. It can also be caused because the trans is worn out/burnt. Inspecting the filter and pan may help determine how severe a problem you have.

There are kits available from the aftermarket to repair the valve body. GM's answer was to replace the valve body.

Sorry I didn't post back sooner. I've been busy.

Thanks for the information Dwayne. What does the kit include and how is it installed? Does the valve body need to be pulled and drilled? I haven't pulled the pan yet so I don't know how bad it is yet. What is the normal mileage of a 4L60 tranny.

 

[gsgns4me]

Sorry I didn't post back sooner. I've been busy.

Thanks for the information Dwayne. What does the kit include and how is it installed? Does the valve body need to be pulled and drilled? I haven't pulled the pan yet so I don't know how bad it is yet. What is the normal mileage of a 4L60 tranny.

Check for DTC's to start with. I know that Sonnax has a kit that requires a reamer.

Mileage is hard to estimate. It depends alot on the service history and usage of the vehicle.

Here's a good PDF on a guys home-made fix for a P1870.

 

[Alky V6]

At that mileage, you should rebuild the unit. Do the Sonnax fixes to the VB also.

 

[1of1547]

Thanks again for the info guys.