1. a 914 transaxle and
2. a 915 transaxle
Stuff I have around:
1. several 914 transaxles
2. two mag-case 7:31 915's (circa 1973)
3. one alum-case 8:31 915 (1984)
4. one early style clutch-type LSD (GT, nearly new)
5. one late style TBD with one AX season on it.
The skinny:
Since I got the TBD (Quaife) I've discovered it's a fine-splined QDF1Q for the later 915/930 application. Now I have one later (aluminum) transaxle and could use it in there directly, but it's a heavier aluminum case version with an 8:31 R&P.
I also have two early mag-case 915's that use the same diff (Quaife QDF5Q or Guard equivalent) as the early 911/914/901 do. Advantages you ask?
1. Mag case is MUCH lighter
2. The bearing bosses are steel inserts rather than using the aluminum in the later boxes, which lessens the need for a one-piece bearing retainer.
3. I can use the stronger late ring-cover plate on the mag case to reduce thrust flex... easier on the R&P. I haven't measured to see if the two plates are the exact same critical dimensions.
I'm not worried about flange splines since I have 100mm Carrera flanges and the reluctor from the late case as well, so no spacer is needed to set up the diff. I'm using GPS for a speedo anyway.
The reason I'm asking:
The spigot on the ring-side of the diff is slightly shorter (.05in or a shade less than 3/16in) and that's ok, however the ring flange is the equally thicker than the earlier diff. So when I shim for that, the ring/bolt-heads might wind up closer to the case on that side. Other than that I think I can space the cover-side spigot to the right dimensions if there's enough wiggle room to get the proper R&P tooth engagement/preload.
Sooooo. I know I can use either earlier style differential in 914 and mag-case 915's. Frankly, I'd rather use the mag case 915 (7:31 R&P) and the LSD but that would require using this late TBD diff in the 914 trans. It's critical dimensions show me it might be adapted but I'm not sure it's worth the trouble (see "reason" below.
Finally, the question:
Have any of you used the later diff in an early case?
My only other option is to swap this late 911/930 TBD for another one that fits early cases directly. That's the easiest solution but not one I have in hand.
Hope this was clear enough. Thoughts?
