Life span of 34 element sprag in a th400

[lazaris]

"Changing out complete direct drum and intermediate sprag assemblies 3 times within a span of 4-6 passes wasn't floating my boat."

How fast were you running when this occurred?

 

[Alky V6]

"Changing out complete direct drum and intermediate sprag assemblies 3 times within a span of 4-6 passes wasn't floating my boat."

How fast were you running when this occurred?

I don't remember. It's been years, now. If I were to guess, I had changed over to the 91mm and didn't have the nitrous tune to spool that turbo down yet. The car most likely was leaving slow and boost was peaking right at the point of making the 1-2 shift. Slow car speed and sudden application of massive torque. I probably hadn't even worked out how much boost I would have to hold back just to keep traction through the 1-2 shift with the sprag flipping so easily. So the boost spike at the time of making the 1-2 shift was most likely pretty massive. The slicks may have been new at the time, also. The track was also holding better back then.

edit: Present day, I have to hold the boost back about 75 kPa (about 11 psi) from the level I could have, just to maintain traction through the 1-2 shift and second gear. Much of the problem is my home track.

 

[jon86]

What 2nd frictions do you use DW CK? if you use borg warner waved frictions and a waved steel it takes some of the hit off the sprag

 

[Alky V6]

What 2nd frictions do you use DW CK? if you use borg warner waved frictions and a waved steel it takes some of the hit off the sprag

The intermediate is not too picky about frictions. If I remember right, I was using BW tans. Could have been playing with HE.

 

[Steve]

A friend has a 34 element spring in his turbo 400 and it has worked flawlessly for 4 years in his 70 Chevelle running high 9's which isn't crazy fast but the car wieghes 4070 pounds with him in the car. He drives the car on the street alot and it only has a 3.70 gear with a 29" tall tire. It has a 515" iron head BBC with a 300 shot right out of the hole. The trans has a stock valve body with a shift kit, blue clutches with kolene steels and the 34 element sprag and is otherwise stock with a PTC 3200 converter.