2002 5.3/700r4 combo swapped into a 68 C10. When I used this combo for towing, I put trans into D3. I was told the trans will use a different set of clutches/bands to hold third and best for heavy towing. I now have swapped in a 2000 4l60e. I know these are the same trans basically, so does the same rule using D3 for heavy towing apply?
Can Tow/Haul mode help here? If so, how?
I have HPTuners to use.
I have exhausted google searching for this answer.
TIA

 

Do some research on the Sonnax HD 2-3 Shift Valve. It keeps the Overruns "on" in all forward gears with the shifter in D3.

I don't personally like this mod, The abrupt coast 3-2 downshift irritates me to no end.

I just run a good Forward Sprag & don't worry about it!

 

The 700R4 has the overrun clutch on all the time when in D3. The 4L60E does not. The overrun clutch comes on when the transmission shifts into 3rd gear. This robs oil on the 2-3 shift when in D3 by bringing on the overrun clutch. In D4 it has no effect. If you do a lot of towing and you are into the throttle a lot when the transmission makes the 2-3 shift, then I would add the Sonnax HD 2-3 Shift Valve. This will make it just like the 700R4. Make sure you are using the Corvette servo and that you grind four slots in the steel spring cover on the second apply servo as TransGo shows in the regular Shift kit, not the HD2. This will help with the 3-2 downshift clunk that Clinebarger mentioned. I do this modification to all 700R4's and the 4L60E when I install this Sonnax HD 2-3 Shift valve. When using the HPTuner, do not make the part and medium throttle shifts abrupt. They should be quick, but not real firm.

 

This is great info guys
Thanks

 

Have I been lucky?
I've never put the suburban in 3rd while towing my car/trailer since 2004.
I've always put it in tow/haul mode.
What does this mystery button on the end of the shifter do?
It must do something cause I'm coming up on 170k now.
I also don't beat the ***** off it while towing either!

 

Your not alone, A late stock SKF forward sprag will last a LONG time if you don't shock or beat on it.