Help..Rear end id

[pooch]

I just picked up an 85 k10 and the rear end isnt right. I am trying to find brakes for it and having no luck. The drum from my 69 fits so I know its an 11x2 shoe.
stamp number TWL K 104 2
casting number 15555879

[mongocanfly]

https://www.chevydiy.com/history-and...differentials/

[pooch]

That site isnt very helpful. It helped find the casting numbers but it has no way to read them.

[sweetk30]

pics help a ton in this case . and unless someone re-geared it there will be a month/year date stamped on the ring gear . so its a good time to service the rear diff for fresh oil and make sure the guts are good inside before you toss a bunch of money at it .

[hatzie]

Look in section 5 of the 85-91 parts book and the sections immediately following the table of contents in the earlier 73-78 & 79-84 parts books for the Rear Axle Identification tables.

11.5"x2" brakes are generally an 8.5" 10 bolt axle on a truck.

TWL is the axle code. TWL is almost definitely not a 1985 axle code.
K is the assembly plant... K = GM of Canada
104 is the day code Built on the 104th day of whatever year TWL belongs to
2 is the shift code. Built on the 2nd shift

The stamp you're really interested in is TWL...

It appears that you have a Unicorn.

I can't find that axle code in the parts books as far back as 1967.
The 85-91 parts book doesn't list an axle code anywhere that starts with T.
I went digging further back in the older books... The first axle codes I see beginning with T are in the 73-78 book but no TWL and nothing in the 42-72 book on GMPartsWIKI.com either.

If you open her up there should be a date and ratio or number of teeth stamped on the side of the ring gear.
This is the starting page of the 73-78 Rear Axle Tables. If you click the picture it should open a new tab or window with this page on the GM Parts WIKI.
The other interesting thing is that there was a Positrac Limited Slip Diff in the 10 series in 73... Not sure what Power Lok is... I'd bet its some kind of locking diff like the Eaton Gov Loc. Later years were only Locking diffs.

[pooch]

It would appear I am looking in the wrong era. It looks like 88-98 wheel cylinder fits it. But the brakes dont work 10x 2.25 is too wide and the 10 in drum hits the backing plate.

I cant post pics because my security token is missing

[hatzie]

I didn't even think of the T400 parts books...
1992 -1993 parts books...

1992 C1 (03-53) A/TRNS(MD8), M/TRNS(MG5), 3.42R(GU6), 8.50 R/GR(SAGINAW)(Y04), * PWR BRK SYS(JB5), HYD PWRDISC/DRUM BRK(JD5), (EXCL/SLIP R/AXL(G80)................. AXLE, RR (3.42 RATI0)(8.50 R/GR)(10 X 2.25 BRK) (STAMPED TWL)

If it's really a 1992 axle it may be a Frankenstein job. Lord knows what backing plate etc got used on it.

[pooch]

Frankenstein....thats what we were thinking. That would explain why there were no rear brake parts on the truck. 10x2.25 drums are too wide. The backing plates would be right for a 92. So the axles must be 1/4 inch shorter than stock
Thanks Hatzie

[hatzie]

Would it be easier to use a rear disc brake setup or source a 10 bolt from a squarebody?

Were your original axles 3.42:1? Your SPID would have a GU6 RPO in the list...

[pooch]

Im thinking of changing the backing plates to something with 2 in wide shoes. It has gears and a posi in it I just dont know what yet. I just put a motor in it so the budget is small. Who would have thought rear brakes would have been this much of a problem

[hatzie]

Originally Posted by pooch

Im thinking of changing the backing plates to something with 2 in wide shoes. It has gears and a posi in it I just dont know what yet. I just put a motor in it so the budget is small. Who would have thought rear brakes would have been this much of a problem

Since it's Frankenstein's monster I was questioning whether the 3.42 ratio of the 1992 rear matched the front axle ratio...
Assuming it has the original Limited slip 3.42 TWL guts still in it...

With this one anything is possible.

[pooch]

I tried the 10in drum today, the center hole is 1/2 in too small for the axles. It definitely has the wrong axles in it. If I can get some time Im going to pull one tomorrow an do some measuring and counting.

[sweetk30]

take a few more pics of the diff center section . leaf spring perches to show if orignal or new welded on for fitment of odd axle to truck . stuff like that .

[pooch]

3 hours on the brake lathe and now it fits. I cut the center to 3 1/2 and cut 1/4 off the back. Trimmed the outside rear to fit in the backing plate. With the help of a 1/4 in spacer it clears and the stock 92 brakes look like they will work.

[hatzie]

Lathes are a sweet tool to have in your arsenal. I love my ancient Monarch Model A and even my little green monster from Harbor Freight.

Hopefully this is the last set of drums you'll need so it's someone else's problem next time.