Where is the Final drive ratio made?

[bradc]

My car will be changing from an auto to a manual this week, does anyone know where the final drive ratio actually is? It is all in the transfer case, and doesn't matter on the diff at all? IE is the 3.684:1 or 4.111:1 ratio done in the transfer case, then the AYC diff at the back is just 1:1?

Next question, can you use a transfer case out of an auto car with a manual gearbox?

[Nick Mann]

I can't tell you for sure, but I would take an educated guess that the final drive is in the gearbox. It seems daft to manufacture different t/f boxes and rear diffs to compensate for the final drive, when it can be done in the gearbox.

My guess would be that the t/f and rear diff will be the same.

I think you need manual drive shafts for the front wheels to replace the auto ones, but I could be wrong.

The one person who will know for sure is Mo. He is the only person I know who has converted his auto to a manual.

[EdmundVR4]

Check the link from Stealth316.com...gearing specs from the 3000GT VR4.

http://www.stealth316.com/2-awd6.htm#Ratios

My son-in-law is using a transfercase from a manual EC5A VR4 on his tiptronic transmission VR4. Seems to be identical.

Copied & pasted from the above link, but it looks a bit confusing when displayed here. Hope this helps.
3000GT/Stealth AWD Gear Reduction Ratios

1991 - 1993 1994 - 1999

Primary
Front differential
Transfer
Rear differential
Speedometer gear 1.375 (44/32)
2.889 (52/18)
0.815 (22/27)
3.545 (39/11)
27/36 1.222 (44/36)
3.166 (57/18)
0.958
3.307 (43/13)
28/36

Overall 3.972 (2288/576) 3.869

Gear Transaxle Final Transaxle Final
First
Second
Third
Fourth
Fifth
Sixth 3.071 (43/14)
1.739 (40/23)
1.103 (32/29)
0.823 (28/34)
0.659 (31/47)
- 12.200
6.908
4.383
3.271
2.620
- 3.266
1.904
1.241
0.918
0.733
0.589 12.639
7.368
4.803
3.553
2.837
2.279


Calculations
Overall front = primary x front diff
Overall rear = primary x transfer x rear diff
Final gear reduction ratio = overall reduction ratio x gear reduction ratio
Speed in gear (MPH) = [RPM x tire diameter in inches] / [final gear ratio x 336]

[bradc]

Nick, I would have thought that too, but from the link Edmund posted up, it looks quite different.

The Primary ratio would be inside the gearbox right? If so then I could end up with something quite interesting. I've pm'ed mo, I hope he knows!

[Nick Mann]

Hmm... don't know the system well enough.

The gearbox connects to the transfer box with a hollow output shaft. See my vbGarage for pics of how it looks when it is mullered! The two front drive shafts come from the gearbox and the transfer box. There is a solid shaft that passes through the middle of the output shaft. I always thought that this was the drive shaft for the front left wheel, coming back from the t/f box, but I can't be sure. If it is, then all the diffs are after the gearbox output shaft, so changing the gearbox will only change the primary. So primary changed but nothing else, still gives you constant wheel velocity all round.

As you said, hopefully Mo knows!!

[zedy1]

ive used my transfer box and diff from the auto and there seems to be no problems

[bradc]

cool now the next important question, on a factory auto with a final drive of 3.684:1, you are doing about 2500rpm at 105kmh, and in a manual it it more like 2900rpm.

In your car Mo, what revs are you at in 5th gear at about 105kmh?