Rear diff identification

[74tiiGolf]

I searched 5 or 6 different terms to find how to identify a diff by the stampings but couldn't find a thing. Any help would be appreciated. Thanks!

Any of this make sense:

33.11-1207 719.0 GGG-40 WH 7 0 3108

Matthew

[instructorbill]

simply divide I think

last four numbers

3108

divide 31 by 08 = 3.875

Whatcha got there is one'a them 3.90:1 rear end jobbies

test it out too... for every 3.9 complete revolutions of the pinion shaft (input side) you will get one on an output shaft

[74tiiGolf]

Excellent! Thanks. A 3.91 LSD. Now it just needs a good cleaning and some Redline.... and a freshly painted car to be put in :-)

Matthew

[TobyB]

Sorry, Bill,

the 3.91 has more than 8 teeth on the pinion!

And the math works out much more closely than that.

How many, I wouldn't try to remember, however.

Turn the input and watch the output- that's the only surefire way.

I load different ratios into 3.91 diffs, so the stampings

really can be wrong...

However, you're looking for 2 numbers stamped on the vertical flat of

the diff, close to the nose.

Kinda random, by themselves, like 11 and 41...

fwiw,

t

[instructorbill]

I do know that there is a string of numbers, four-long either in the front or at the end of the line that division of the numbers yeilds the ratio... I did however give the way to check the math by checking the number of Input revolutions:output

Not to offend, and not offended.

I didn't know that the second number is the number of teeth on the pinion gear, good to know. Also I didn't know that those numbers were elsewhere on the case-- this too, good to know

[Beaner7102]

There should be some stamped numbers high up on the drivers side of the diff about 1/2" big but very fine stamping - thats is stamped NOT cast(under the crud). Numbers like (11 40) (10 41) - these are the ratio 40÷11=3.64 - which means its a 3.64 diff. You can open the back and count the teeth for the same result (number of teeth on the crown wheel, divided by number of teeth on the input shaft). Have fun with it, Beaner7102

[Bill_Riblett]

There should be some stamped numbers high up on the drivers side of the diff about 1/2" big but very fine stamping - thats is stamped NOT cast(under the crud).

Note: the stamped numbers are on the passenger on left hand drive cars!

The stampings are not very deep and are often obscured by crud and rust.