flubyux2

This is just an FYI, for future reference. im posting this up since i couldnt find it and i had to discover the hard way that the MT driveshaft wont bolt up to the AT diff, and vice versa... i just assumed that since im doing a 5sp swap, i just use the MT driveshaft and itd mate up to the rear diff... i mean, Thats how we do it on Supras; it only makes sense right? guess not...

"normal" measurements, from centers of bolt holes
AT diff pinion flange driveshaft bolt circle: 3.808"
MT diff pinion flange driveshaft bolt circle: 4.107"
Diff pinion flange bolt hole inside diameter: 0.392"

Outer measurments, from outsides of bolt holes
AT diff pinion flange/driveshaft bolt circle: 4.5"
MT diff pinion flange/driveshaft bolt circle: 4.2"

im keeping the Auto diff in this swap and mating the MT driveshaft to it. i like top end, as does the guy who im doing the work for. ive opted against waiting another 3-5 days for an MT diff pinion flange to swap into the AT diff to allow direct bolt-on of the MT driveshaft. instead, im going to use an air grinder w/ a carbide bit to slot the existing holes on the AT diff to allow the MT driveshaft to bolt on.

EDIT: the bolt holes on the Auto diff pinion flange cannot be easily modified to accept the smaller diameter of the 5sp mt driveshaft. there is a raised lip on the backside of the pinion flange which is situated to be right against the flat of the bolt heads used to attach the driveshaft. this ridge would also need to be cut down to a smaller diameter to allow the DS bolts to sit flush against the pinion flange, let alone provide the support fuction it's originally intended for. short of removing the flange to have it turned on a lathe, the only solution short of buying the 5sp diff pinion flange is to slot the holes of the 5sp DS or use the AT DS. im honestly not comfortable slotting the holes on the 5sp DS since there is very little material there to do so...

hopefully people researching future Auto to manual / 5sp swaps in the future will come across this and find out EXACTLY what needs to be done instead of vague/enigmatic posts like i did.

badddrx7

iTrader: (7)

You are correct again. I also looked at modifying an auto diff flange to accept the manual driveshaft flange and saw that ridge in the back. I opted to buy the correct manual flange in all three of my swaps. I have heard of others modifying the auto flange but I feel it is too risky. The flange is a balanced unit and grinding/drilling could cause driveline vibrations.

Later

flubyux2

yeah... the better side of me said to leave it alone and and get the manual diff flange but the guy needs the car by monday. i ended up marking the diff flange w/ the 5sp DS and slotting the holes. once i did that, i used a 3" diameter cutter to trim back the ridge, stopping every few seconds of grinding to make sure i didnt take off too much. at the end of it, it fits just as tight, or tighter than stock. my clearances are almost nil with no play between the holes in the DS and the holes in the pinion flange when the bolts are pulled thru (untightened). all the cuts are virtually identical so any imbalance should be 0.5 grams or less.

just for reference, when i get piston engines balanced, "precision" tolerances are within 0.5 grams as well. for a rotating mass spinning 6000-7000rpms to be ok with 0.5 gram imbalance; a smaller, lighter mass spinning at half the speed should be perfectly fine, in theory. ill post up when i take it on the freeway and let you know how it turned out.

my only regret is not being able to get the nut loose on the flange and turning the flange down on a lathe