Question for rear housing gurus

[RodnRudy]

So I advertised my 68 C10 rear end in the for sale section. Housing is stamped HA which is 3.73 gear ratio. A member said he would buy it but only wanted the ring&pinion, carrier etc. I agreed and yesterday pulled the carrier and pinion gear out and lo and behold the thing is a 2.76 gear ratio! It must have a series 2 carrier from a later than 72 12 bolt truck rear? I did some searching and found some one had an '85 truck rear with the 2.76 ratio. Question is will the later carriers inter change with the earlier 67/72 rear housings? Needless to say the sale went south but the buyer was glad I checked before I sent it to him. Pics of parts and housing stamp below. Tooth count on the pinion is 17 and on the ring gear is 47.

[harpo231]

HA is 3:73 no listing for 2:76... is a 2:56 and 2:73 ,but your gear tooth count matches none of them....

[RodnRudy]

I typed "2.76 gear ratio in C10" in the search window and the only posts mentioning that ratio were for later, '75-'85 trucks. One even mentioned the ratio was standard in the diesel C10s. I'm just surprised the 2 series carrier will work in the '67/'72 rear ends. That rear gear would make a good cruising one. Maybe I'll throw it in the for sale section. Lol

[ZEKE68]

My 1981 C10 had a 12 bolt 2.73 ratio rear end.

[Shaky]

The book shown below, by Randy's Differentials, is one of the best tech books I've ever read.

He lists three carrier variations for the truck 12-bolt:

Two-series: 2.56-2.73

Three-series: 2.76-3.42

Four series: 3.73-4.10

I've never encountered a truck two series or a 2.76 in the wild...

[LuckyScott]

I would think that would be worth a lot of money. Lots of guys don't have a overdrive trans and would like better fuel milage in their truck. I would buy it myself if I didn't just rebuild mine.

[RodnRudy]

Originally Posted by Shaky

The book shown below, by Randy's Differentials, is one of the best tech books I've ever read.

He lists three carrier variations for the truck 12-bolt:

Two-series: 2.56-2.73

Three-series: 2.76-3.42

Four series: 3.73-4.10

I've never encountered a truck two series or a 2.76 in the wild...

Shaky,thanks for the info on the carrier I have. I just assumed it was a 2 series because of the 2.76 ratio.

[alsriv2]

I just discovered my '69 has a 3.07 limited slip installed instead of the HA 3.73 gears. It is good as it keeps the RPM's down on the new 396BB that is in there. Makes for a great cruiser where I am only pulling 2600RPM at 70mph, but terrible at lower RPM performance. When I bought the truck, the PO and my own research showed that the truck had the 3.73 installed, but neither of us actually opened up the rear end to count the teeth.

[Daves70]

I have a 12 bolt gov lock with a 2.73 ratio. It came out of an 81 I believe.

[demian5]

Originally Posted by alsriv2

I just discovered my '69 has a 3.07 limited slip installed instead of the HA 3.73 gears.

Thats awesome, I lost the pinion on my posi 3:73 and found a guy selling an open carrier and beautiful 3.07 R&P for $100 on CL.