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**lks dcvn** · 01-22-2007, 01:36 PM

I had the same problem awhile back...

After driving for about 30+ mins the car starts to shift violently on the 1-2 upshift and if not corrected it would throw a SEL (Service Engine Light) with a code of P1870.

What many mechanics will say - bad tranny, needs rebuild, needs replaced, etc. If your tranny has 130k miles on it then - yes- it may need a rebuild by now, but that is not what is causing the harsh 1-2 shifting when warm.

The real reason for the problem is the valvebody - it needs to be corrected (and if done early enough in the life of the tranny - it won't cause damage). The real culprit is the TCC regulator valve. You NEED to replace the regulator with a Sonnax TCC Valve Regulator Valve Kit found here - quarter of the way down - after #43G. **NOTE: I have no affiliation with this website nor have I ordered anything from it - I merely used it as example to demonstrate the parts and their numbers

There are two different Sonnax kits:

Sonnax #77754-03K - 93-97 (except EC3) - 4L60E (roughly $40)
Sonnax #77754-04K - 98+ including EC3 - 4L60E (roughly $40)

To do this repair correctly - you need to find a shop that has the correct Sonnax Reamer (#7754-R2 - $105-$140) to correct the valve body problem and replace the TCC regulator and sleeve with the updated parts. If they are familiar with the Sonnax kit to fix the 4L60E - they will also likely have the reamer already.

You do not have to drop the transmisson to have the valvebody fix completed - a knowledgeable shop can likely do it, but ask them before dropping it off (if you are not doing it yourself).

If you have the transmission rebuilt and they DO NOT fix this valve body issue - The problem WILL come back.

A short-term fix - when the harsh shifting occurs - pull over and turn off the truck for about a minute - then crank up the truck again and the harsh shifting is gone (for the time being) - this resets the valvebody and allows for normal operation again, but the problem will come back if driven for long enough again.

Hope that helped- now back to my turn signal problem...

Tom

01-22-2007, 01:36 PM	#13
lks dcvn Registered User Join Date: Jan 2007 Location: Columbus, Ohio Posts: 4,338	Been there - Done that! I had the same problem awhile back... After driving for about 30+ mins the car starts to shift violently on the 1-2 upshift and if not corrected it would throw a SEL (Service Engine Light) with a code of P1870. What many mechanics will say - bad tranny, needs rebuild, needs replaced, etc. If your tranny has 130k miles on it then - yes- it may need a rebuild by now, but that is not what is causing the harsh 1-2 shifting when warm. The real reason for the problem is the valvebody - it needs to be corrected (and if done early enough in the life of the tranny - it won't cause damage). The real culprit is the TCC regulator valve. You NEED to replace the regulator with a Sonnax TCC Valve Regulator Valve Kit found here - quarter of the way down - after #43G. **NOTE: I have no affiliation with this website nor have I ordered anything from it - I merely used it as example to demonstrate the parts and their numbers There are two different Sonnax kits: Sonnax #77754-03K - 93-97 (except EC3) - 4L60E (roughly $40) Sonnax #77754-04K - 98+ including EC3 - 4L60E (roughly $40) To do this repair correctly - you need to find a shop that has the correct Sonnax Reamer (#7754-R2 - $105-$140) to correct the valve body problem and replace the TCC regulator and sleeve with the updated parts. If they are familiar with the Sonnax kit to fix the 4L60E - they will also likely have the reamer already. You do not have to drop the transmisson to have the valvebody fix completed - a knowledgeable shop can likely do it, but ask them before dropping it off (if you are not doing it yourself). If you have the transmission rebuilt and they DO NOT fix this valve body issue - The problem WILL come back. A short-term fix - when the harsh shifting occurs - pull over and turn off the truck for about a minute - then crank up the truck again and the harsh shifting is gone (for the time being) - this resets the valvebody and allows for normal operation again, but the problem will come back if driven for long enough again. Hope that helped- now back to my turn signal problem... Tom