After taking many measurements multiple times using different methods, I determined that the end of the 71C tail shaft is 2" farther back than the 71B. This being the case, I had my drive shaft shortened 2". No one locally here in Knoxville Tennessee could shorten a metric drive shaft properly, so I sent it to Carolina Driveline in Spartanburg, SC. They charged me $60 + shipping to shorten and balance the shaft.
The original was 22.5" between the yoke centers and the shortened one is 20.5".
Note that the dust sleeve on the slip yoke has to be removed. It will not fit over the tail of the 71C like it does on the 71B.
The dust sleeve is a thin wall tube that is shrunk on to the slip yoke flange and then spot welded in 2 places. To remove it, I measured down into the sleeve and then marked the distance to the slip yoke flange on the outside of the tube near the spot welds. I used a cutoff wheel on my angle grinder to cut the sleeve down to near the spot welds on both sides being careful not to cut into the flange underneath. Next I ground down the spot welds with the edge of the cutting wheel until the dust sleeve was free of the slip yoke.
The transmission mount on the 71C is about 1-3/8" farther back than on the 71B. Because the rubber isolation mount has a slight offset between the crossmember stud and the transmission mount holes, I was able to to get about half of the movement I needed by simply reversing the isolator. My mount uses the crossmember that bolts vertically to the bottom of the car so all I had to do was re-drill the mounting holes in the crossmember to get it to line up. I believe the crossmembers on the cars with the horizontal bolts would be more difficult and will probably require some cutting and fabrication.
My crossmember
The later style crossmember
The finished installation
I hope this is useful information. I've put about 300 miles on the new transmission and really like it. If you have any questions or suggestions for this web page, email me at heimsothtn@comcast.net and I'll try to help.
Steve Heimsoth.
Clinton, Tennessee (near Knoxville).
Smokey Mountain Z Car Club member.
Transmission gear ratios:
| GEAR | '72-'76 F4W71B | '77-'79 FS5W71B | '80 FS5W71B | '81-'83 FS5W71B | '84-'98 FS5W71C |
| 1st | 3.592 | 3.321 | 3.062 | 3.062 | 3.321 |
| 2nd | 2.246 | 2.077 | 1.858 | 1.858 | 1.902 |
| 3rd | 1.415 | 1.308 | 1.308 | 1.308 | 1.308 |
| 4th | 1 | 1 | 1 | 1 | 1 |
| 5th | - | .864 | .773 | .745 |
.759 |
| Reverse | 3.657 | 3.382 | 3.026 | 3.026 | 3.382 |
Overall ratios with various differential gears:
3.364 My original transmission
2.55 11.38
GEAR
'72-'76 F4W71B
'77-'79 FS5W71B
'80 FS5W71B
'81-'83 FS5W71B
'84-'98 FS5W71C
1st
12.08
11.17
10.30
10.30
11.17
2nd
7.56
6.99
6.25
6.25
6.40
3rd
4.76
4.40
4.40
4.40
4.40
4th
3.36
3.36
3.36
3.36
3.36
5th
-
2.91
2.60
2.51
Reverse
12.30
11.38
10.18
10.18
3.545 My 280ZX transmission My 240SX transmission
2.69
GEAR
'72-'76 F4W71B
'77-'79 FS5W71B
'80 FS5W71B
'81-'83 FS5W71B
'84-'98 FS5W71C
1st
12.73
11.77
10.85
10.85
11.77
2nd
7.96
7.36
6.59
6.59
6.74
3rd
5.02
4.64
4.64
4.64
4.64
4th
3.55
3.55
3.55
3.55
3.55
5th
-
3.06
2.74
2.64
Reverse
12.96
11.99
10.73
10.73
11.99
3.700
2.81
GEAR
'72-'76 F4W71B
'77-'79 FS5W71B
'80 FS5W71B
'81-'83 FS5W71B
'84-'98 FS5W71C
1st
13.29
12.29
11.33
11.33
12.29
2nd
8.31
7.68
6.87
6.87
7.04
3rd
5.24
4.84
4.84
4.84
4.84
4th
3.70
3.70
3.70
3.70
3.70
5th
-
3.20
2.86
2.76
Reverse
13.53
12.51
11.20
11.20
12.51
3.900
13.19
GEAR
'72-'76 F4W71B
'77-'79 FS5W71B
'80 FS5W71B
'81-'83 FS5W71B
'84-'98 FS5W71C
1st
14.01
12.95
11.94
11.94
12.95
2nd
8.76
8.10
7.25
7.25
7.42
3rd
5.52
5.10
5.10
5.10
5.10
4th
3.90
3.90
3.90
3.90
3.90
5th
-
3.37
3.01
2.91
2.96
Reverse
14.26
13.19
11.80
11.80