87 SWB 2WD R10 rear gear

[blublazn86]

I have recently purchased an 87 2wd r10 truck with a 700R4 trans and I was curious as to which gears were in the rear diff so i pulled the cover and did the counting and division thing and what I came up with blew me away....it has a 3.25 gear ratio!!! Is that a common gear or not?? I've seen 3.73 3.42 but never a 3.25 gear in one. Anyone have any insight to this??? Please help!!!!! Thanks

 

[dhamp]

YOu sure?? Never heard of thatt one.

 

[blublazn86]

Yeah...I just thought that was kind of odd!!!!!!!

 

[dhamp]

Maybe re-count the rotations???

 

[89Suburban]

Isn't there a 3.23?

 

[RetroC10Sport]

Only available ratios stock in 1987 are 2.73, 3.08, 3.42 and 3.73...

 

[82chevyk10]

Any chance it may not be a chevrolet rear end.

 

[HotRodPC]

There is a 3.21 gear ratio in the 14b Full Float rear axle. There is also a 3.23 gear but it was not OEM in GM 1/2 trucks. It was however OEM in some GM cars and aftermarket. Is it possible you don't have a truck rear end in the truck? Has anyone maybe upgraded to a Ford 9 inch for racing? What was your teeth count? I'd say you most likely have 3.42 if its OEM in 87.

 

[GreaseDog]

There is also a 3.23 gear but it was not OEM in GM 1/2 trucks. It was however OEM in some GM cars and aftermarket.

my dad's '99 Silverado has 3.23 gears in it, which despite being an "8.6" 10 bolt" will bolt right into an earlier 8.5"...

 

[HotRodPC]

my dad's '99 Silverado has 3.23 gears in it, which despite being an "8.6" 10 bolt" will bolt right into an earlier 8.5"...

I'm not suprised about that. I should have been more clear. It wasn't available as an option in OEM squares. Its even possible it might be available in aftermarket for OEM square rear ends.

 

[GreaseDog]

just saying, it could be an actual set of GM gears, so it would appear 100% factory.

 

[HotRodPC]

, which despite being an "8.6" 10 bolt" will bolt right into an earlier 8.5"...

You know, I've heard this too. I wonder if the 8.6 is actually stronger than the 8.5??? Its only .1 bigger, and that's nothing to get excited about, but if in the gear design, if the girth is bigger, it can certainly be a much stronger gear. Although it could be a smaller girth in the gear too. I'd be interested in finding that out. One of the big reasons I always prefer a 3/4 ton truck over a half ton, is cuz back in the day when I raced trucks and built motors and transmisisons for them I had a hell of a problem keeping rear ends and driveshafts in trucks. Finally when I went to a 3/4 ton truck with a Dana 60 full float axle, a much thicker 2 pc driveshaft with a bigger carrier bearing, I quit tearing **** up and got the power to the ground. Granted, I lost a hair of ET for the added weight but never broke anything, and also liked the firmer stiff truck like ride.

Oh yeah, I ate up carrier bearings in the half tons. A damn brand new bearing, and the torque would just twist the bearing right off its housing perch. Never had the problem with the 3/4 carrier that actually bolted on both sides, instead of 2 bolts in the center of a pedestal.

 

[GreaseDog]

You know, I've heard this too. I wonder if the 8.6 is actually stronger than the 8.5??? Its only .1 bigger, and that's nothing to get excited about, but if in the gear design, if the girth is bigger, it can certainly be a much stronger gear. Although it could be a smaller girth in the gear too. I'd be interested in finding that out.

its the same exact gear...

3.73 gears, looked them up for an 8.5, and nearly every one of them lists "8.5/8.625"

 

[HotRodPC]

its the same exact gear...

3.73 gears, looked them up for an 8.5, and nearly every one of them lists "8.5/8.625"

Ahhh, so its same/same then. I was actually hoping the 8.6 might be a thicker gear but still fit the same carrier. Actaully that doesn't matter anyway. Its usually a carrier that will break before a gear will, not always but in most cases. I just figured if I ever had a 1/2 ton race truck I'd have to get it fitted with a Ford 9inch and run Weld Wheels since they have both Chevy and Ford bolt patterns. I'm a bit old for that kind of racing now anyway. Think I'll stick to the Olds sleeper in the 3/4 ton and not break a thing.