78 Mustang drive train swap

[weRmustangs2]

  Hi guys. New to forum and greener than an Irishman on St. Paddys day. Son has a 78 Mustang (No drive train in) that was originally a 302 Windsor model. We have pulled a 302 and M97LE box out of a donor EL Fairmont. I believe that the original box would have been a C4. My question is, Will this combo fit or is the bell housing too big? I have tried to install and seems to keep fouling on the fire wall and cross member. Is the C4 bell housing smaller? Think I ma need to change transmissions or cut out the tunnel and modify.

[67FBGT]

Is there a data sticker on the door or door jamb at all? If so the codes on that would tell you what the car left the factory with.
People on here will be able to decipher the codes for you.

[weRmustangs2]

Hi, Have done the VIN Decoder thing before. 1978, Dearborn MI, Mustang 2 door 4 passenger hard top Ghia (Vinyl top has been removed), V8 302-2v 139hp. Spoke to a local mechanic today who told me to toss the M97LE trans and replace it with a standard C4 unit. Told him that the research I had done so far said that the bell housing was altered in some way from a standard C4 and may also not fit. Not sure if this is actually the case or not. No examples locally to check on.

[67FBGT]

So the data plate doesn't tell you the trans and rear axle? The data plates / stickers on the early cars do.
The C4 auto in my '67 is from a '77 Mustang and is actually the C10 variant (different dip stick arrangement - goes into pan). It bolted up to my 302 quite normally so I'm not aware of different bell housing sizes but Ford seemed to make numerous versions of just about everything so who knows.
Can you borrow a C4 from a Mustang club member to test fit? I'm sure someone will have a spare sitting around.
Not that many Mustang IIs around so as you say it's not easy to find another car to compare to.

[GEOFF289]

Ford didn't introduce a 4 speed auto until 1980 so I reckon your car rolled out of the factory with a C4 in it (assuming it was an auto).

However, this article http://www.mustangandfords.com/how-to/drivetrain/1305-how-to-understand-and-identify-automatic-transmissions/ indicates that Mustang II's got a C4 with a "unique bellhousing and 148 tooth flexplate".

I would think that this means a smaller diameter plate so it's possible this unique bellhousing was physically smaller than other C4's - maybe it needed to be to fit in these cars.

[67FBGT]

Info in that article states:

There was also a C3, a light-duty, French-produced three-speed used in the Mustang II. It looked similar to the C4.

I think you'll have to ask around locally and see if you can borrow a C4 either regular or with small flex plate for a test-fit. Any auto trans repair shops around your way who might have something sitting out back of the workshop?

[GEOFF289]

C3 was only used in 4 cylinder and maybe V6 Mustangs and Pintos which were built on the same platform.

[Husky350]

In regards to the BTR 4 speed you tried to fit, they are a shitload bigger than a c4.

[scedd1]

In regards to the BTR 4 speed you tried to fit, they are a shitload bigger than a c4.

But i didnt have any trouble fitting a BTR in my 68, which originally had a C4, so you would thinkl the tunnel is the same in a 78.

[GEOFF289]

See post 4 above. '78 tunnel may be smaller.

[peter9231]

The BTR is not much bigger just the rear crossmember mount is a couple of inches out.
Side by side they are the same length.
The case diameter is a couple of centimetres bigger.
I have one in my 66 with only a crossmember mod.
Peter

[cap70]

looking from the front a c4/c10 has the starter mounted to the bell housing on the left down the bottom, from what I can see of the tranny you are trying to fit the starter is mounted on the right and up high. this could be causing your firewall clearance issue.

[Husky350]

Geez I remember looking at the c4 and btr side by side and the bellhousing was a fair bit bigger, but it could have been the whole starter motor thing.

[shaunp]

Do you have the right sump on the engine? Just a thought may the engine wont drop down to where it needs to be

[jiffy]

My thought would be - if you have a newer, 4-spd auto, I would be trying to mod the tunnel and fit that. It’ll be a better driving experience