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Posted by: vintage914racer Oct 13 2010, 09:53 PM

In anticipation of my first tranny rebuilt, I tore apart a core transmission over the last couple days. The stamps on the gears are not decipherable, so I'm hoping you can help me determine what the gears are based on the number of teeth.

3rd-5th have 31, 29, and 27 teeth respectively. What gears am I working with? I looked at the charts but they don't make sense to me.

Posted by: echocanyons Oct 13 2010, 10:05 PM

you just have to read http://www.914world.com/specs/regearing_901.php page it is very comprehensive.

The spreadsheet has a list of all of the gears ID'd by teeth.

Posted by: echocanyons Oct 13 2010, 10:12 PM

The numbers you refer to don't add up but the stock and most common are N, V, ZD for 3rd, 4th and 5th.

here is the list cut from Race914's page with the numbers you listed


Third
HB 19 : >31 1.63
I 20 : > 31 1.55
J 21 : >31 1.48
KA 22 : >31 1.41

Fourth/Fifth
M 22 : >29 1.32
N 23 : >29 1.26
P 23 : >27 1.17
Q 24 : >27 1.13
R 25 : >27 1.08
V >27 : 25 0.93
W >27 : 24 0.89
XA >27 : 23 0.85

Posted by: vintage914racer Oct 13 2010, 10:16 PM

Which number corresponds to the teeth on gear among the pair of numbers separated by the colon (29:22 for example)?

Posted by: ppetion Oct 13 2010, 10:19 PM

wish i could help! good luck buddy

Posted by: echocanyons Oct 13 2010, 10:21 PM

You need to count each gear in the paired gear set.

Posted by: Richard Casto Oct 13 2010, 10:46 PM

That page is a great resource. BUT... If you are having a hard time understanding the spreadsheet you might want to look at this as it might be a little more simpler and easier to understand as it doesn't try to cover as much material...
http://www.roadglue.com/wiki/index.php?title=914_transmission


As mentioned above, each gear, is a set. One is on the input shaft and one on the output (pinion) shaft. So for example a stock first gear on a 914 uses an "A" gear set which as a ratio of 11:34 (3.091). If you looked at the input shaft, you would see a small diameter gear with 11 teeth, while on the output shaft, you would see a large diameter gear with 34 teeth.

So if you look at the chart on the 914 Wiki, the number on the left of the colon would be the teeth count for the gear on the input shaft and the number on the right is the teeth count for the gear on the output shaft.

Assuming you kept everything organized and know what gears are which, you should be able to count the teeth and match them to the chart. When I rebuild a transmission, I document the what gear sets are used and in what locations they are installed in prior to pulling them off the shafts.

Posted by: vintage914racer Oct 14 2010, 10:01 PM

After further investigation I've determined the core tranny I tore apart has stock gearing.

Posted by: Joe Ricard Oct 15 2010, 08:24 AM

Now go find a box out of a 912 and steal 4th and 5th. This will make a nice short gear set with ZD 3rd. short 4th and short 5th. Of course you will be running 4000 RPM @ 75 MPH.
Which isn't bad if your motor can spin to 7500.

Posted by: vintage914racer Oct 15 2010, 02:55 PM

My primary transmision for the car, which I plan to tear into within the next week, has short gears into it and once I tear that one apart I'll know what I'm working with. I'm hoping for MSX, but we'll have to see.

The problem I have with short gears, though, is that Road America is my primary track so I need gears for the ~mile long straights too.