l6conv

I have a 71 w-30 with a rear end code of TDB . Can anyone tell me if it"s correct for this car. Thanks

oldsmobiledave

Sorry but that is not an Oldsmobile differential.


Is that an 8.5" or an 8.2" 10 bolt or is it a 12 bolt Chevy?

jensenracing77

Just be sure you are looking in the correct place. In 71, it is the first year to be on the "front of car" side of the passenger axle tube.

l6conv

I did not buy the car new , but I"ve owned it since 1993 and that rear looks to be original to the car. But it could have been changed at some time. I will try to get some pics today of the code and the rear cover. Any other pics needed to ID this just let me know. Thanks

oldsmobiledave

It was a 22 year old car when you bought it so it is entirely probable that it received a swap.


You did not say if it is a 10 bolt or a 12 bolt.


All W cars were built in Lansing & as such this would originally have had a TM code (3.42) or TO code (3.73) 8.5" 10 bolt with bolt in axles. If it is an a/c equipped car then it will have a 3.23 geared diff (can't remember the axle code off the top of my head).

l6conv

its a 10 bolt posi with 3:23 gears it does have a/c looking at the picpictures can you tell me what this rear end is

monzaz

10 bolt 8.5 Corporate rear for sure.
TDB only thing I came up with is a 1971 truck axle code of TDB which is 4.11


I doubt that is correct...Could be one of those goofs from the factory...too many REEBs before work....lol. Jim

monzaz

Quick question. IS the code upside down on the passenger axle tube facing the back of the car?

monzaz

axle code TD was used in the Olds but in 66 67 axle housing assembly...It was always a Anti Spin code.

I would have to say some one goofed at the factory OR someone stamped that into the tube. ...see if you can find any other code anywhere else on the tube...??? Jim

l6conv

Jim Yes the code is upside down facing the bottom of the axle tube.if it helps any there are two ribs that run straight on the center section of the housing. I will look for other codes or numbers today. Are there any numbers inside where the ring and pinion are that would help?

monzaz

On the edge of the ring gear outer diameter there will be tooth count and ring part number and even a date code on the gear if it is still original GM.

THAT is the only true way to know what ratio is in the rear.

AS far as IDing if it is a ORIGINAL to the car rear. ??? It is a 10 bolt 8.5 rear for sure. I am sure Olds used the scalloped covered 10 bolt 8.5 like the BUICK SKYLARK.... But I have seem MORE round cover 10 bolt 8.5 rears with 12 -3 oiler in the cover under OLDS Cutlasses than the scalloped cover. (IE attached picture)

l6conv

Thanks for the info Jim I"ll check the ring and pinion numbers today. Would the type of the posi unit tell you anything? Thanks

Fun71

Here's what the code on my '71 10 bolt rear looks like. That's the spring perch on the left and the vent tube at the top of the picture.

197110boltR2256opendiffcomp.jpg

l6conv

Thanks Kenneth I"ll check the front of the axle tube .

l6conv

Did'nt find any other codes on the axle tube. I took the rear cover off and saw some numbers on the ring gear but could"nt read them very well,ran short on time so I"ll check it tomorrow.I did find the code TD in my 67 service manual. It was for a wagon with 3:23 posi.My 67 vista has a different rear but the same gear ratio and its code is GM.

Gumby

I too have a '71 442 W-30 with a TDB rear axle. Specifically, TDB 345 stamped on the right tube facing down. It's a 10 bolt with a W-27 aluminum cover.
The rest of the drivetrain is all original - block, intake, exhaust, heads, tranny, etc..

Anyone have any idea about the TDB 345 rear axle?

Fun71

I'm pulling from memory here so this may not be 100% accurate, but from what I have learned, the code shown above on my 1971 rearend translates as:
R2 O068
R2 = 2.56:1 ratio, open differential
O = Oldsmobile Division
068 = Julian date (68th day of the year)

So yours would be:
TD = gear ratio and carrier style (I don't know the decode for TD)
B = Buick Division
345 = 345th day of the year

If any of this is inaccurate I hope someone will correct me.

Gumby

Kenneth,

What years did Buick use those codes? I forgot to mention, an inch or so to the right of the 345 is a 1. Does that indicate 1971?

rogerw30

I also own a 1971 442 W30 with a/c. The differential code is TDB 020 1 (3.23 for a/c cars). I have owned car since 1986 and the differential appears original to the car. It also was built with 1970 fenders from the factory.