Need some education regarding my '99 van

[whwright]

Hi guys.

I have a 1999 Chevy conversion van with a 5.7L and 4L60E. I need to use the van to trailer a car my son bought on eBay from Wisconsin to Oklahoma City. I asked a friend who happens to be a transmission mechanic if this would be a problem, and he suggested that I keep the tranny out of overdrive when I'm pulling the loaded trailer. He said the empty trailer wouldn't be any problem at all.

When I asked him what difference it makes whether the tranny is in "D" or "OD" he simply replied "it just does." It's kinda beside the point, but he also mentioned that if it had a 4L80E transmission "we wouldn't be having this discussion."

Can you educate me a little bit? Why does being in a higher gear put more strain on the transmission?

Thanks.

Wayne.

[ZR2DK]

I BELIEVE....if you pull in OD, the gears in your transmission will be spinning a lot faster than if you pull in 3rd, which in turn will wear your transmission faster. Now I am not a mechanic, nor do I claim to be, but I am fairly confident that this is correct. It would be like you pulling a wagon full of weights while running (OD) vs. pulling a wagon full of weights while walking (3rd gear). You'll burn yourself out a lot faster if you try to run, and so will your tranny.

Forgive the retarded description. Like i said, im not a mechanic. If this is incorrect in any way, delete it so no one gets confused. Thanks.

[urethane dino]

OD vs D towing concerns the lock up convertor. In OD the TC will lock and unlock many times causing excessive wear to the TC. This is the same issue whether you have the 4L80E or 60E.
Towing in D the TC will still lock up, but at the higher RPMs it wont hunt around when you step on throttle.
Now in my opinion, while going down grades for longer periods, especially on the interstate, you can slip it in OD with out to many worries, and just manually downshift to D or 3 as needed.
Dino

[John DiMartino]

in addition to what Dino said,the reason the 4L60E isnt good for towing heavy in OD is the 3-4 clutch pack,and the 2/4 band arent very strong either.The band can slip pretty easy in OD.thereare aftermarket 4th servos available to increase the holding power of 4th gr,but stock dont tow heavy in OD.

[whwright]

Thanks for the education. I felt certain that there is a better reason than "it just does."

Wayne.