skirkland1980

iTrader: (2)

Running a th350 non lockup 4000 stall converter, Hughes transbrake. Did all the modifications recommended in the transbrake instructions. Machined down low reverse piston and direct piston for 5 clutches, used red raybestos frictions etc. I also replaced all the bushings, used extra bushings in the sun gear. Pump was inspected and was in excellent condition and reused. I used the wavy plate on the intermediate piston as recommended by Hughes to protect the roller clutch. Problem is that all the clutches and steels still looked like new except for intermediate. Intermediate steels had burnt spots and little chunks of the frictions missing. This transmission only has about 30 1\8 mile passes on it. Power is around 500hp? Never been dynoed. Runs 7.28@104 mph. Doesn't feel like its slipping and 1-2 shift feels good. I would suspect direct clutch failure before intermediate. Any ideas? Thanks

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skirkland1980

iTrader: (2)

Been thinking about the fluid. I'm using standard type F. Wondering if I should use some sort of racing atf. What y'all experts think?

sofakingdom

iTrader: (1)

Not claiming to be an expert, I've only ever rebuilt maybe a dozen or so of those, but... not the fluid.

Sounds almost like it's not fully disengaging after it shifts to 3rd.

What are the pressures in the various gears? What was its clearance when you stacked it up?

Pro Built Automatics

Type "F" fluid has apx. 13 - 17% less holding power on Dynamic clutches (shifting clutch). So do not use it. Use Dexron III or Dexron VI at the least, along with some tractor type oil for longer life. Make sure that the 2nd gear clutch clearance is no les than .040", as these clutches are on the large side. As long as the line pressure is where it is supposed to be, I would think that this would fix it.

skirkland1980

iTrader: (2)

Thanks. I believe the intermediate clearance was around. 080". I didn't check pressures before teardown because there was no indication of a problem. Thanks for the info about the fluid. What do you mean by tractor type oil?

sofakingdom

iTrader: (1)

Tractor type oil = hydraulic fluid

Some of the trans builders call for that exclusively.

Never heard that before about type F fluid; but I'm no expert, as I said. For all the years I was growing up, we called it "shift kit in a can". (tells you how far back THAT goes) It's thicker than GM fluid, and has more of the clutch additive in it, which you'd understand why, if you ever build a Frod transmission. Their clutches are about 2/3 - 3/4 the diameter of GM ones, meaning around half of the inherent holding power. But as I said, I'm not an expert, that's just opinion.

Be that as it may, .080" is toward the high side, but still within the range of reasonable clearance. The piston should be able to move far enough to take it up, maybe a bit slowly, but you would have noticed that (slide-bump 2nd shift); and it's PLENTY wide enough that the clutch should COMPLETELY disengage when pressure is removed.

Any possibility there could be a leak somewhere; between the direct clutch and intermediate? such that, when in 3rd, some non-zero amount of fluid was still getting fed to the intermediate? what about its bleed orifice? could it have been holding fluid enough that it never disengaged fully after shifting to 3rd?

skirkland1980

iTrader: (2)

Thanks. I did a Google search and found guys saying they use John Deere hy-gard fluid. Only thing I can think to do with pressure testing is do an air check when I reassemble.