I have been trying to find out what ratio differential my '65 Cutlass has as I want to change from an open to a LSD. I couldn't find anything on the outer axle tube but I figured that it may not be correct anyway as it could have been replaced at some stage.
The diff's outer cover has a small stamped "035" about an inch or so from the center of the cover which seems fairly random.
On the back of the component that the ring gear is bolted too there are a number of markings as follows.
1) A fairly large number 4 that has been cast proud when the diff part was manufactured.I read somewhere about there being a 3 series and a 4 series component because of the different thickness ring gears.

2) Underneath the letter 4 are the numbers "358" also cast proud but smaller in size. Alongside the 3 and the 8 are what I take to be marks left by a punch but they look a bit like the number 1 so it could be 13581 but I don't think so.

3) Next are the numbers 304 and possibly the number 6 at the end but it isn't clear.These small numbers were also cast proud.

4)The stamped letters ARM STEEL.The L is not clear.

5) The medium sized stamp number "3".

I have spent a lot of time today trying to figure this out but I have found nothing concrete so I am hoping there are others who may have been down this track and been more successful.Please excuse the pun!

 

OPEN THE REAR AND ALL IS CLEAR.
if it is factory gear the tooth count will be stamped into the outer ring gear diameter edge ...if it is aftermarket it could be stamped or you can count the gear.

EITHER way if you are unsure if the rear has been tampered with you need to physically check the gears...only true way to know.

Jim
JD

 

Thanks Jim,
As per my previous all of the info I provided was from looking at the diff with the cover off.It makes sense that it would be stamped on the edge of the ring gear so I must have missed it yesterday.I hope it's there because to count the teeth accurately I would have to remove the ring and pinion from the housing. Off to the shed I go.

 

take some pictures while you're there. That will really help folks identify what you have.

 

Pictures YES... You should be able to count with a piece of caulk and spin and count. the pinion ...Jim

 

You were spot on! On the edge of the ring gear is the following
4 013 GM 265 P O There is the space between the 4 & the 0 but as the rest of the numbers are smaller and neater than the 4 I think the 4 was stamped in at time of installation and the rest cast in.

Moving on if I divide 13 into 40 I get 3.0769 or rounded up 3.08.
Have I got that correct?
If I have I can now go and pick a LSD carrier that will fit. Awesome!

 

Hi again Jim, as per my previous post after figuring out that I have a 3.08 diff ratio in my Cutlass I have decided to buy an Auburn Gear 5420114 HP Series Cone type LSD Carrier from Summit Racing.Something interesting I found while looking through the Factory Service Manual was that Oldsmobile used the Auburn cone type carrier in the 33 series cars and the (Eaton?) clutch type in the 52 series vehicles. I wonder why? Maybe you might be able to shed some light on that. Well better get moving and spend my US$622- ouch. Thanks to all.

 

Well, I have ordered the Auburn cone type LSD carrier from Summit but now I am wondering what else I may need in the way of consumables or parts. For instance do I need new carrier bearings? Anything else I should do while I am there?

 

ALL just the American business contract...lol. That is a lot of manufacturing and GM FORD Chrysler all made contracts to get the parts made. Probably NOT a reason at all other than a bid and a promise to get a certain number supplied by a certain date.

Jim
J D

 

Now you are on your way to 2 wheel peel.

The 114 Auburn will come with carrier bearings YOU MUST USE them for that unit to fuit the 8.2 10 bolt rear.

This carrier was a modified unit for some reason Auburn has always used it this way???

DO NOT think just DO...

 

Thanks for the info. I was wondering whether the bearings were a must or a nice to have, now I know. Pity Summit don't warn their customers about it.
The Auburn unit doesn't come with carrier bearings and there is a problem with the Timken LM501349 bearings (apart from the fact that the bearings don't come with races) in that they are a extra part they suggest I buy and supposedly fit my '65 Cutlass but when I check the application the model year only goes down to 1968 which I know was a year a number of changes were made to A body cars eg Wider frame rails etc
Also a number of customer reviews all got the wrong bearing for their application.
Here is a link to the bearings
https://www.summitracing.com/int/par.../model/cutlass
As Summit want US$52 to deliver the bearings and a diff cover gasket I am trying to source them in New Zealand but I guess now I had better find out which is the correct bearing and race. I assume I need 2 bearings for the install?

 

Where did you get this Auburn posi unit from?
You got ripped off.

I have the part numbers BUT the posi unit should come with Limited slip additive, Ring gear bolts, and 2 bearings and 2 races. Timkin or Koyo brand
You need LM102949 and LM102911 x2 on each
Then the posi unit will bolt right in.

Next time BUY FROM THIS SITE ... We will not do you wrong and if price is slightly higher NOW YOU KNOW WHY.... JIm

J D RAce

 

I have the cover gasket and bearings here too. BUT SUMMIT should have had those parts in the box. I would call them and complain....CALL up Auburn Gear and ask them what comes with that part number ...YOU will see.

They can not sell it with out a disclaimer as it will NOT fit any 10 bolt 8.2 with out those bearings and races...1964-1972 NONE will fit with out the bearings and races they include in the box and the reason they include them...

 

The carrier bearing they have list is CORRECT for a STOCK BOP CARRIER...not THE 114 AUBURN UNIT.