4 speed questions

Putting the arm in the bell housing it looks like the TO Bearing is about an inch short of clutch centerline. Did they make different length arms for small block cars? Using a cast iron bell housing.

View attachment 31990

Ford used two different arms on the 71/ Mustangs.

429's used C8AZ-7515-A (ID# C8AA-7541-A) yellow paint dot, 12 7/16" length

250, 302, 351's used C8AZ-7515-B (ID# C8AA-7541-B) green paint dot, 12 5/16" length

Hope this helps some! Good Luck with your project.

Ford used two different arms on the 71/ Mustangs.

429's used C8AZ-7515-A (ID# C8AA-7541-A) yellow paint dot, 12 7/16" length

250, 302, 351's used C8AZ-7515-B (ID# C8AA-7541-B) green paint dot, 12 5/16" length

Hope this helps some! Good Luck with your project.

Click to expand...

Yep, That is a big help. Hard to believe Ford would make 2 arms that are only an 1/8 inch different in length though.

Guys- if the only difference between the two is one is big block, then the difference is the input shaft size and block size.

I think a SB fork is a small block fork and a big block fork is a big block fork...

Is a C8AA-7515-B could replace a C8AZ-7515-B fork?

Ford used two different arms on the 71/ Mustangs.

429's used C8AZ-7515-A (ID# C8AA-7541-A)  yellow paint dot, 12 7/16" length

250, 302, 351's used C8AZ-7515-B (ID# C8AA-7541-B) green paint dot, 12 5/16" length

Hope this helps some! Good Luck with your project.

Click to expand...

Yep,  That is a big help.  Hard to believe Ford would make 2 arms that are only an 1/8 inch different in length though.

Click to expand...

The big block input shaft is 1 3/8" diameter, requires a larger "fork" and throwout bearing.

Since you are getting ready to put in I will offer a suggestion. You might already do this but lots do not. One of the PITA things about putting transmission in is getting the input shaft threaded through the throw out bearing, clutch disc and into the crankshaft. 

I take some cheap low grade bolts several inches long and cut the heads off, angle the ends. I thread the studs into the two bottom transmission bolt holes in the bell housing. Then you can get the transmission up and onto the guide bolts and have the transmission in gear and something to turn the tail shaft with. You can rest on the guide bolts and rotate the shaft as you slide in through throw out bearing clutch disc and into the crank.

As a teenager I broke 16 transmissions in one year so I changed a lot of them.

Knock on wood, never blew and engine but broke lots of transmissions, clutches, driveshaft, rears and axles.

Hello Manu Mach1,

Unless you have dealt with the Ford numbering system on a regular basis, the use of engineering numbers vs service part numbers can be a source of confusion.  Ford NEVER stamped, molded, or printed the actual part number on any part. What you see on the part is an Engineering number which was used both on the assembly line and at the Consumer/Dealer level. This was a way of helping to identify a part where there may be several that look the same but have functional differences.

Some clutch forks may have 7541 or 7515 but will cross to the 7515 which is a service part basic number.

In your case, the engineering # C8AA-7515-B crosses to the service part number C8AZ-7515-B. So both numbers are for the same part. The C8AZ means that the full-size Ford powertrain engineers were given the responsibility for the design of these Forks.

C=Decade, in this case, 1960's

8=Year of release, in this case, 1968

A=Model or product line originally released. in this case the full-size Ford

Z=Engineer office responsible for the release, in this case, a service part

The letter after the basic number is usually a design or revision level. With this part, "B" just happened to be the next letter available since "A" was already in use for the C8AZ-7515-A which was the full-size Ford with 427,428,429 engines.

I hope this is not too much number overload! 

Thanks Secluff, looks like you know a lot about those Ford numbers.

Well, I have my answer, thank you