700R4 towing

How much do you guys feel is safe to tow with a 92 &00 R4? Should one keep it in "D3"?

Not knowing what your wanting to tow makes it kinda hard to answer.

Assuming it’s an open car hauler or a 20ft boat, small camper and your transmission is in fair shape with 160k miles on it. I would add a nice trans cooler and let it eat. Take your time and drive normal. It will work until it doesn’t.

The answer is in your owner's manual.

"Not much" and "Yes" would be my answer.

I pulled a car trailer carrying a Trailblazer, before that the trailer carried a Chrysler Mini-van, with my '88 K1500 and 700. Both times the load went 30+ miles at highway speed. I'm also on my third transmission, and both of the first two had completely totaled planetary gears--broken teeth, etc. The second transmission had all the lining of the 2--4 band laying in the trans pan.

But I have reason to believe that the towing load wasn't the reason for the two trans failures.

I once brought a squarebody Suburban home on a trailer, pulled by my stepmom's '91(?) C1500, on about a 350+ mile trip. I took it -really- easy in D, not OD, and was surprised it made it. Dad being a former transmission builder/shop owner I guess he had more faith in it than I did, or just knew he'd be able to R&R it quickly if it croaked. It was the truck we had available at the time, not what I would have chosen had there been other options. These are light duty transmissions, not built for towing.

Edit, huh, just also realized that same truck took me on a much longer trip with a tow dolly to bring back a Mitsubishi Diamante from a police auction. I think I've tried to selectively block that memory as it was not fun. I'd gone from TX to GA to pick up a pinball machine from a friend. That was nice, but I injured myself breaking down the machine for travel, then had to carefully wrap it and load it with a messed up hand. Then to AL for the police auction and get the car loaded. Cars at the lot were packed like sardines and the Diamante didn't run. Had to push it several car lengths by myself, only able to open the door about 1 foot, and couldn't roll the window down. Get it up to the dolly and load it using a come-along, then the trip back to TX hoping the trans wouldn't pop.. jeezus what a run that was.

Richard

WCJr's 700R4 was slipping shifts, but I still used it to tow Roscoe home. It actually shifted better with the load on the trailer. My '99 Suburban with 4L60E had no problem towing my Jaguar to Omaha and back. My race team captain's 4L60E GMT900 towed our race car and gear from Dallas to Atlanta and back without a hitch.

That said, it's a light duty transmission and not suited for anything but light and infrequent towing. I don't know if D3 is going to help, other than keeping you towing at a slower speed.

Towing in direct vs OD lightens the load on the 3-4 clutch pack for one, for 2 it ensures the trans isn't hunting from 4-3-4 all the time. I've towed cars on trailers in D and OD with a couple 4L60 trannies and it didn't kill them. Flat towed a good 5000#+ in D with a 700R4. All but the one in our Envoy Denali eventually died, but not with a trailer out back.

I would think 4-5k in the hills is no problem in 'D'. Flatlands over 50mph will be fine in 'OD". A good trans cooler is a great addition to ANY trans.

I would not use overdrive at all personally. Stick to 3rd regardless of what is behind the thing. I did not even use OD around town. GM should have never used the 700r4/4L60E piles of garbage in these trucks at all. They are barely adequate for a 4.3L S10.

You think they're weak now? They used to be so fragile/brittle as to be totally unusable. The early TH 700-R4s used to pop when used behind 2.8L V-6s in S10s and Camaros. Grandma drivers would fail them in Caprice Classics with 4.3 V-6s. The TH350 was considered a "heavy-duty" trans in '84 when I was in a Chevy dealership. Numerous companies sold crossmembers and "conversion kits" to remove a '700 and stuff in a TH350.

By '88, they'd made about a hundred upgrades, many of them "major" to the silly thing. It was ALMOST a transmission by then. But not one suitable for a full-size truck.

Isn't there some issue, perhaps a BIG issue, with the cooling circuit on the 700R4 when the TCC is unlocked, e.g, as might be likely when towing (esp. in 4th)?

I seem to remember that the transmission fluid flow through the cooler circuit is diminished / negated when the TCC is unlocked. The obvious consequence is that the transmission overheads b/c (a) the TCC's unlocked and so slippage losses are high (when towing in particular) and (b) the flow through the cooling circuit is compromised.

Can someone check me on this?

Assuming I'm right, when towing one should be certain to operate with the TCC locked when at all possible. Towing in 4th, in particular, may cause extended operation with the TCC unlocked, as the throttle position may be too high to enable TCC engagement. I've seen this happen on a 4.3L S10 auto I once owned.