901 Transmission

[BigD9146gt]

This question is for all those who have rebuilt at least 20 of the 901 gearboxs before (can be the same box too)...

I'm curious about all of these products on the market like the billit intermediate plate, 904 main shaft, and other products that people clame to strenghten the 901 gearbox for increases in power. I've rebuilt a hand full of transmissions now (And i want to here from people that have done this more than i have), and the only accutal area i've seen fail are the bearings in the intermediate plate... but never the plate itself. And the 904 mainshaft, what makes it stronger, if you cut the thing in half, wouldn't it still have the same cross section of material (excluding the 2nd gear spot... which would be smaller in diameter over a stock mainshaft w/a gear already cut onto it. But all the diameters for clutch spline, the needle bearing just after the diff, gears 3-5, the double ball bearing in the intermediate, and finally the spline for first gear... aren't they all the same???? So how can it be stronger... is it chromoly? Titanium? or are people graduating with their engineering degree online and an opinion?

[Bleyseng]

I thought the 904 mainshaft available from Ottos was larger in diameter.
Don't know what a stock 904 shaft looks like.
The aluminum intermediate plate is used with larger engines with lots of torque. I think the larger motors crack the stock plate.

Geoff

[Dave at Pelican Parts]

I am not explicitly qualified to answer your question, but I believe that the aluminum intermediate plate is supposed to keep the input and pinion shafts better located than the stock magnesium one.

I don't know how well it works, if at all...

--DD

[BURN-BROS]

Do a search on the topic, its been covered quite a bit

[red-beard]

In the rebuilds I've done...

The upper intermediate plate bearing (the smaller one) usually is the one that goes. Next is the one below it. I've seen 1 bad roller bearing, pretty sure it was the upper bearing. 1 completely destroyed speedo shaft nut (someone used an air chisel to remove it, but then reused it!). Broken pinion gear, broken ring gear, lots of corrosion and of course lots of used up sliders, synchro's and dog teeth.

I have yet to see any broken intermedite plates, or side covers or shafts. I did have one damaged case, but the lower ball bearing cage self destructed and that cage is steel! I've had a couple of tranny's where the input shaft would not separate after removal of the castle nut.

I have one tranny, a 914/6 unit, where I cannot remove the detent spring cover/retainer. The threads are gone underneath, but are preventing the removal. I need to fix that one!!!!

James

[SteveStromberg]

When we build 901's that will take over 300 hp we swap the plate and change the bearing for a different type that is much stronger. Also modify the housing for more strenght. The 904 we sell is made out of much stronger steel that a stock main shaft. If you need more info just send me an e-mail. Steve

[sammyg2]

I know the answers but I've only rebuilt one 901 so I can't tell you.