anyway to tell which ring and pinion in trans?

whiteSC59 · 03-29-2010, 08:36 AM

ive got a trans that appears to be a mag case gearbox as its turned that smoky grey/dark color and has the mechanical speedo. i was told its from an SC but cant verify because the bottom flat plate is scraped clean of its numbers. im hoping for an early 915 with the 7:31 ring and pinion so im looking for any other ways to tell its guts...thanks. ps. this isnt the one thats advertised for sale in parts for sale section by the way.

Bill Verburg · Bill Verburg's Garage

Quote:

Originally Posted by whiteSC59

ive got a trans that appears to be a mag case gearbox as its turned that smoky grey/dark color and has the mechanical speedo. i was told its from an SC but cant verify because the bottom flat plate is scraped clean of its numbers. im hoping for an early 915 with the 7:31 ring and pinion so im looking for any other ways to tell its guts...thanks. ps. this isnt the one thats advertised for sale in parts for sale section by the way.

w/o taking it apart the only way is to put it in a gear(it would help to know which one) and cont the turns as accurately as possible at the input and out put shafts

for instance both of the following have mg cases
a 915/02 from a '72 or '73 w/ 7:31cwp will turn 14x at the input for each turn at the output when in first, in 5 it would be ~3.3:1

a 915/44 from a '76 w/ 8:31 cwp will turn ~12.3:1 in 1st and ~3.2 in 5th

the lower the gear the greater the disparity

whiteSC59 · 03-29-2010, 10:08 AM

bill, Im not a mechanic so if i take the differential out can i tell then? im gonna try and count the turns but maybe easier to open it up...? regards, m

KTL · 03-29-2010, 10:53 AM

If you take the diff out, you'll know without question what you have. With the diff out, you simply count the teeth on the pinion.........

manu72S · 03-29-2010, 01:29 PM

exactly, you have just to count the number of teeth on the ring and pinion. You can identify the gears used by visiting inside by open the cover on the bottom side

Matt Monson · 03-29-2010, 01:58 PM

Before you take it apart look at the bellhousing. If the mainshaft guide tube is bolted in it's probably an 8:31. If it's got a throw out arm on it that's bent and has a "horseshoe" spring on it, again probably an 8:31. Also, if it's an SC gearbox it will have fine spline output flanges, not course spline flanges.

manu72S · 03-30-2010, 05:23 AM

put some pictures about it