If a 700R4 tranny needs a lockout to pevent overheating why doesn't that apply to my TH350? Just wondering.

John

John, its "lockup" and it is an electrical lock on the torque converter, after 4th gear is reached, the converter is "locked" to keep heat down in the converter. Th350s did not have the lockup converter. GM did make very few TH350 lockup versions, TH350C if I remember right.

I think it was intended as a fuel economy thing. Reduced heat is an added benefit.

in a 350 the oil circuit is different and it cools more in regular drive. in a 350c tranny oil circuit is different and if lockup doesnt work it will make more heat. being hotter oil and burning up tranny. in a 700r4 it is made to have lockup. if you get a converter with no lockup you need to modify tranny so it will get more cooler flow.there for cooling tranny down more.

Thanks fellas. After doing a lot of reading I think I'll install a tranny cooler seeing as heat is a bad thing.

John

i always put a hayden cooler on there part number 1405. and bypass radiator it is big enough to handle all heat and cool tranny down. but it might get some bad reviews out of this because some say put it through radiator to heat fluid up.ive rebuilt transmissions for 23 years and done it this way with no effects on trannny.

If a 700R4 tranny needs a lockout to pevent overheating why doesn't that apply to my TH350? Just wondering.

John
Non lock up torque converters have three pieces, lock ups also add a clutch to that. Non lock up converters slip, this slipping creates heat. A lock up converter doesn't slip when clutch is engaged. It's the slipping clutch of the L/U converter that creates the problems, when it burns the friction material off and distributes it thru out the trans.

To hereitis67, I agree, I've never heard that T fluid has to be XX degrees to work. I've never heard what is too hot for it either. Many of us drive for 10 years and never hurt a trans, others can't drive for 10 minutes.:D

Jeff