P1870 code - TransGo kit repair ?

[NoReverseYukon]

So, this code popped up a couple times over the last week. I read that it is commonly caused by wear in the PWM/TCC valve area on the valve body. I bought the TransGo SK 4L60E valve body repair kit. The instructions seem rather straight-forward, except for 1 thing that has me stumped. When it comes to drilling out/oversizing the holes in the separator plate - For example, if I am only installing a new PWM/TCC valve, should I only drill out the 2 holes that feed that valve, or should I drill out all the holes as the instructions show?

If anyone who installed this kit could chime in, I would greatly appreciate any advise.

Thanks

 

[Mudsport96]

I havent done the SK kit, so idk what holes they show being drilled.
I have done 3 4l60e HD2 kits, and some of those holes affect the shift speed.

 

[Mudsport96]

I tried to look up the sk kit instructions and didnt get far. Can you put up pictures or scans of the instructions and maybe we can figure it out From there

 

[NoReverseYukon]

The diagram in my instructions looks similar to this :
Should I drill out all holes, or just those 2 that relate to the PWM ?

 

[Mudsport96]

Ok, so those are the same as the hd2 kit. So, it depends, you dont have to drill them. It depends if you want a little firmer and quicker shift and not the soggy slide shift these have from the factory.
In a heavy tahoe/Yukon i wouldnt go to the largest size, but somewhere in the middle. I love a firm crisp shift, my old blazer would bark the 32s on the 1-2 shift... my wife hated it.
So it will come down to if you are okay with how it works now and just fixing the pwm issue, or juicing it up a little with ( in my opinion) how it should have shifted from the factory by drilling them MODERATELY lol

 

[NoReverseYukon]

I sent an email to TransGo and this is their reply :

Hello Matt,

The redesigned ISO-CONV valve is not a stand alone component / fix for the TCC slip issue.

The new design requires an increase feed at the balance end, combined with an increase in AFL pressure as well as a slight increase in line pressure in order for it to work as intended. These changes, in turn create a need for the recalibration of clutch feed orifices size, accumator springs, servo springs, etc.

Everything in the kit has been precisely calculated to work together in unison. In other words, everything in there has to dance together at the same pace and to the same tempo.

I strongly advise against trying to install only part of the kits not listed as optional in the instructions.

Robert Moreau
Technical Sales and Marketing Support Specialist
TransGo El Monte, CA

So, I guess I'm lucky in that I didn't tackle this repair last weekend, as planned.

 

[Mudsport96]

Ok, so i guess if your instructions show needing to drill more than the pwm holes, you should drill them. Honestly, i have never installed a kit WITHOUT drilling all the holes. Just follow the size chart and youll be fine