Those trannies got a bad rep because they got used in the Blazer and burned out alot.
The engine in the Blazer is way, way too small, so the tran does alot of shifting - UNLESS (and I learned this the hard way) you have the throttle cable set right.
(needs to be set so the tran won’t shift up unless the engine r’s are higher)
Actually, the post-87 (88-up) trans are all fixed and have an excellent rep now. You can get them built stronger than a 400, if you so desire.
I’m putting one in the Jag this year.