3 OTT and 3:08 gears

[72SB]

Anyone running this set up?

If so is "feathering" (slipping) the clutch required in first?

Looking to reduce FWY RPM's

Current gears, 3:73, 12 bolt truck

My understanding I need to switch to a 2 series carrier to go higher gear ratio other than 3:73

[Warrens69GMC]

Tire size has a big impact on the rpms. what tire size you running?

What engine and how do you use your truck?

[jimijam00]

If you got torque, you need not worry about having to "feather" the clutch.

[72SB]

Have a 250 6 cyl

Yes aware tire size affects RPM. Current 235/75 x 15's BFG's

with the 2.85 1st, was asking if anyone is using a 3:08 rear gear with 3 OTT

I drive Fwy often so would like to run at 70mph vs 55 mph and be under 3k rpm.

Using RPM calculator, the 3:08's do that

[Warrens69GMC]

I have a 1978 c10 with 350 /th350 and 3.08. It does do well, but you need more torque from the 250 to get there IMO. Consider a 3 speed with overdrive instead of a new rear end/gear change.

[jumpsoffrock]

Honestly I think you're gonna be just fine, don't switch trans, don't add OD, just slip the clutch a bit.

As long as you really do mostly hwy driving.

[72SB]

My 67 Camaro TH350 has 2.52 1st gear and I have 3:08 in that car. Yeah it makes over 400hp and TQ....so it will just boil the tires

Given the Saginaw 2:85 1st gear I suspect the 3:08 will be "normal" clutch engagement although I suspect won't just go off idle releasing the clutch now as it does with 3:73's

Completely aware of other trans swap possibilities, just asking if anyone has 3OTT and 3:08's and what initial clutch release is (read does it require feathering or slipping)

[tutone]

I ran that exact setup in a 68 back in the 80s. With the 250, you had to feather a bit but that engine was tired. I replaced it with a healthy stock 1972 350 and it lasted for years. I think you will be fine.

[Steeveedee]

^ Agreed. I had a '69 Camaro (admittedly, it had a 327) with a close-ratio Muncie (2.20:1 low) and a 3.08 axle. It worked just fine; got good mileage when I kept my leg out of it and had a crazy top end.

[68panelman]

Subbing on this

[Palf70Step]

My 70 is a 3OTT with 3:08 rear. Granted I have a 350, but no issues driving normal. IF you are going to pull or haul heavy loads you then may be slipping clutch to get it rolling. My last truck was a 250 6 with 2.73 rear gears and no issues with it either. Just no low end umph, but drives just fine.

[A1971Blazer]

My Dad bought a new truck way back in 79....350 3OTT.....3.08
not a lot of clutch slipping normally...... but a lot trying to pull his boat up the ramp...

[special-K]

I don't have this combination. But I can't imagine not being hard on the clutch. I tried a 3.08 rear with a Muncie 4spd and felt that was too high pulling out. Went with 3.42s for a happy medium. I started off with 3.73s and was looking for better cruising gear. The thing I never liked about the 3spd is tall gearing down low. Not just off the line in 1st, but taking slow turns in 2nd gear too.

[jumpsoffrock]

Originally Posted by special-K

I don't have this combination. But I can't imagine not being hard on the clutch. I tried a 3.08 rear with a Muncie 4spd and felt that was too high pulling out. Went with 3.42s for a happy medium. I started off with 3.73s and was looking for better cruising gear. The thing I never liked about the 3spd is tall gearing down low. Not just off the line in 1st, but taking slow turns in 2nd gear too.

Man a new clutch every 50-80k miles sounds cheaper than a full trans swap or even a basic rear gear change if done by a shop.I know it wouldn't cost an arm-and-a-leg for a gear change but that's not what this thread is about.

It sounds like a few people have managed with the setup the OP is asking about.

[special-K]

I do my own work. There's more to it than cost anyway. It's drivability. That was the question. I was giving my impression of the combination asked about by referring to another combination that should work better, having a lower first gear and closer ratios throughout (also a 325hp 350). I've had 6cyl/3spd trucks with 3.73 and couldn't imagine running 3.08s. I guess GM agreed. I never knew of anyone running that combination until this thread. Different people get different impressions. Mine is no thanks.

[71meangreenc10]

Originally Posted by 72SB

Anyone running this set up?

If so is "feathering" (slipping) the clutch required in first?

Looking to reduce FWY RPM's

Current gears, 3:73, 12 bolt truck

My understanding I need to switch to a 2 series carrier to go higher gear ratio other than 3:73

Did the exact swap you are asking about. Yes on the 2 series carrier, and you will be Good to Go. I run 275/60/15's on mine and it runs fine. Original 250 6cyl, 3 OTT , 3.73 rear, Now 283, 3OTT, 3.07's or 8's depending on the day...Clutch works fine. Now go to a 2.76 and the truck will not pull itself over a curb without straining....(Been there, done that)....

Smitty

[72SB]

^^, thanks for the comments on your set up

The 2 series Yukon though is the biggest cost. Its a peg leg now. This truck may see a V8 swap at some point but for now the 250 six runs fine so will get to the gear/carrier swap. My 30 spline axles will work with the Yukon diff

https://www.summitracing.com/parts/y...ckup/year/1972

Gears:

https://www.summitracing.com/parts/m...-308?rrec=true

Bearing Kit:

https://www.summitracing.com/parts/m...rmkt?rrec=true

[jimijam00]

I'd go drive a truck with the exact setup I was considering before I spent a bunch of money and time on modifying the rear end.

[71meangreenc10]

Originally Posted by 72SB

^^, thanks for the comments on your set up

The 2 series Yukon though is the biggest cost. Its a peg leg now. This truck may see a V8 swap at some point but for now the 250 six runs fine so will get to the gear/carrier swap. My 30 spline axles will work with the Yukon diff

https://www.summitracing.com/parts/y...ckup/year/1972

Gears:

https://www.summitracing.com/parts/m...-308?rrec=true

Bearing Kit:

https://www.summitracing.com/parts/m...rmkt?rrec=true

Mine is a Open Carrier, I don't mind the Single Wheel Solo. It is a good cruiser that way for me. I changed everything and moved the engine to the V8 position when the 283 went in. I don't pull anything with it anymore so I am not worried about clutch slippage. I got enough trucks to do truck stuff. My C30's are going to be some great builds.


Smitty

[HO455]

This may be a cheaper option for you. Not my transmission. Just offering an alternative.

https://seattle.craigslist.org/sno/p...565561671.html