DaleClark

iTrader: (55)

Hey guys -

I've got a real stumper here.

I've got a project car ('94 base manual) that I've been putting back together. I got the car with no drivetrain in it, and the whole drivetrain in various boxes and bins. I've got things mostly back together, but the driveshaft and diff flange are stumpin' me.

The car came with an automatic diff - previous owner had a Kaaz LSD in his diff that he hated, and bought the automatic diff to eventually swap the gears out and make another stock manual diff. I got just the auto diff, bought a set of 4:10 gears, and had a shop put the gears in and set the diff up properly. I also got from the previous owner a manual diff flange - so far, so good.

The driveshaft I got with the car ONLY lines up with the automatic flange. The bolt pattern is different on the manual flange, like aftermarket rims with 2 sets of bolt patterns drilled in them.

So, I figured I got an auto drive shaft, and I needed a manual. Got a manual driveshaft from a local guy, and guess what? The two are the SAME. Same length, bolt pattern, everything.

I either have a flange on the diff that's from something else entirely, or something else goofy . I also have an old non-turbo 2nd gen diff in the garage, and it actually lines up with that flange, which makes me think about using it.

Attached are some pics. Looking at the pics, I need to confirm a few things -

- What driveshafts are these? Are they DEFINITELY manual driveshafts? The service highlights book states there's about a half inch difference in length between the two driveshafts, but the measurement they have doesn't say where you start and stop measuring . In the pics you should be able to see the measuring tape.

- Is this definitely an auto flange? It has the rubber isolator between the two halves, and the bolts are captive in the flange.

- I also have a pic of the non-turbo 2nd gen flange - the manual flange I used is similar in design, and you can easily remove the bolts from the back of the flange, which I know is normal on manual tranny diffs from doing various clutch jobs.

Sorry for the wordy post, but I hope someone can help shed some light here.

Thanks a million,
Dale

RotaryResurrection

iTrader: (8)

Dale,

An AT driveshaft for an FD has an even fatter front yoke than the FD manual/FC AT/FC turbo. This makes it easy to spot. And yes, an FD AT driveshaft will only mate to an AT diff flange, and vice versa. I have done a manual swap keeping the auto diff and slotted the holes in the flange to make it work.

badddrx7

iTrader: (7)

Dale, what you have in the third pic is a manual differential flange, but the bolts have slid around from their original opening. I suspect the center dampener has loosened and rotated. The 4th pic is an auto diff flange. I have done three auto to manual swaps and here is a picture of my latest auto differential with a MANUAL flange mounted on it with 4.3 gears inside. The Auto driveshaft is longer than the manual and fatter. The auto driveshaft flange holes will not line up with that third flange picture. But will with the 4th pic.

Later

BluRR

iTrader: (1)

If you check your manual in the drive train section the lengths of the auto and std shafts are given. If i remember correctly the auto is about an 1inch shorter or something. But anyhow the length is given from center to center of the 2 cross and bearings.

DaleClark

iTrader: (55)

Thanks a bunch, guys! That finally put the mystery together - what I thought was the auto flange was the manual flange. Talked with the previous owner last night, and he ran the auto diff for a while in his car and had swapped the flange over without even thinking about it.

Is the fact that the flange is rotated a Bad Thing? He was making a LOT of horsepower in the car back in the day (single turbo, huge fuel system) and drag racing, I wonder if that twisted the flange?

Dale

badddrx7

iTrader: (7)

Dale , I would not run a flange that been altered such as that. Call on Fritz and get another one or solicit the forum. Better to be safe than sorry later. Part does not cost an arm and leg.

Later

flubyux2

im having trouble deciding what to do about this 5sp to Auto thing too. i took some measurements of the AT diff and the 5sp ds to find out exactly how much they differ.

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/mt-diff-flange-measurments%3B-5sp-swappers-703281/

i still dont have hard numbers on driveshaft lengths tho.

EDIT: i found those numbers
https://www.rx7club.com/showthread.p...veshaft+length