Is anbody using a kit like the one found here (https://transmichigan.com/catalog/pr...products_id=97) I've heard that 700R4's arn't durable enough to handle WOT 3rd to 4th shifts. Just wondering if anybody runs a 3rd to 4th WOT kit.

 

I used to have WOT 3-4 in my 88 IROC. Never had a problem. Somebody had done something to the transmission before I got it though. It shifted hard and had 3.45 gears in the back.

I've never heard of a Corvette having trouble with a 3-4 shift and there are thousands of them out there with automatics.

I picked up one of Pro Built Automatic's street/strip shift kits for the 700R4 in the GTA and he included a valve that has the part throttle holes blocked off. Haven't installed it yet. Probably will in another week or two. Another handy benefit is that the car won't shift back into 3rd gear at 90+ mph unless you manually shift it into 3rd (I like that).

Haven't heard of the valve in your link, but since it's a Sonnax part, I would assume it's beefy and strong. I see they blocked the part throttle shift hole (which controls the ability of the WOT 3-4). That's good. I'd stay away from the B&M kickdown valve that many people buy. All that does is raise the mph that the 4-3 shift occurs at. So instead of 120 mph, it's more like 140 mph. (an easy way to blow up your engine or transmission)

Seems like most of the earlier 3rd gens will do the 3-4 shift but most of the later 1980's models wouldn't. Not really sure why that changed.

 

it changed when the warranty claims started coming back.... The standard stock clutch packs and servo's aren't really up to the task of WOT 4th gear. OD was never meant for performance. 1:1 is the highest performance top-end ratio, as using OD requires pulling and extra set of gears thus negating performance.

 

But how hard would it have been for GM to have made a better clutch and servo? It couldn't have been expensive. Heck, the B4C transmission package used to be for sale for $15 before it was discontinued. As is right now, my SuperRam 350 would lose a top speed competition to a stock 305 5 speed.

 

The 4th servo is easily adequate though there are several aftermarket billet 4th gear servos that can be easly swapped to give 30-40 percent more hold that stock on the band, But As I said the servo and band are not the weak like here but rather the 3-4 clutch . We all know the 3-4 clutch factory setup in the 700r4-4l60e is weak . But generally people only associate it with 3rd gear. But in fact its also transfers power and actually due to the higher gear more stress is put on it. But any transmission with and upgraded 3-4 pack and large boost valve should be able to handle the WOT 3-4 shift no more that it would actually be used in most cars.