my dad's 91 has the 727 and we've worked that thing hard, the only problem we've had with it is the trans shop put a bad converter back in on the rebuild at 200,000 because the clutch packs were starting to slip. it's got 10k of utility bed/tools and has pulled quite a few trailers.

 

That would work fine for a GM transmission, but ours don't use vacuum. They use a cable to regulate line pressure, the same cable that signals kickdown operation as well. On the 727s (that our 47's are based off) used a linkage to regulate line pressure and kickdown. And the line pressure can't be any higher than what the pump can create, and that is limited by engine RPM...back to the weakness of having an automatic behind a diesel. At 1000 rpms, there just isn't enough pressure being created by the pump (on a stock transmission) to handle the torque being produced by a modified engine.

Jim

 

I guess you did not read my complete post. as stated you need manifold vacume so you would need a vacume pump and a vacume regulator on the throttle ie GM and FORD on there early diesels. and I will say it again it can make more than enough line pressure to hold our engines at 1000 RPM unless you have a big internal leak. RPM is a function of voluim and the regulator system is pressure control!! also as stated the vacume system also controls shift timming as does the cable or linkage on the chrysler units and not just kickdown.as to the amount of line pressure needed to hold have you ever compaird the two as to the amount of line they run? I think you might be suprised just how close they are and line pressure can either be your friend or enemy as there is a direct line as to pressure rise and heat.


bill
rebuilding transmissions since 1971