Does anyone know what years they made such a thing? I've heard tell of "turnpike cruiser" options that had them. Prepping for massive road trip in a 70 Newport with either a 2.76 or 2.94 or thereabouts but have a notion that some 2.45-ish gears would be my cheapest overdrive-ish option. Anyone in Maryland/Virginia have a small yoke set they'd part with?

They had ratios like that for the 8.25 and or the 9.25.
But iirc 2.76 is the lowest for the 8.75

Maybe a taller rear tire?

We ran a 68 newport vert on the power tour one year, the milage probably would have been better if we left the 3.23's in instead of the 2.76's. We were loaded heavy with three adults and three kids plus luggage! We got about 10 mpg average with a 440 auto and 2.76's

The pinion gear gets larger as the number gets smaller. A 4.10 pinion is smaller than a 2,.76. The 8.75 housing is tight with a 2.76 and because of that, no other pinions taller than 2.76 will fit.

The cheapest thing I can think of is tall tires.
235 75 15 is 29"x9". They do fit.
If your already there then your ready to go...

The first reaction is to think of lowering cruise RPM. Go further and think of torque multiplication.

What will the car weigh fully loaded on the trip? How much power & torque do you have. Wagons and trailer tow cars had 3.23 gears, not 2.76.

I thought there was a lower ratio offered, rare, but a gas crisis/mileage brute force OEM solution. I might have been confused with the as already mentioned, the other rears. But if one was willing to even slightly reduce the effective ring diameter, and still use the same 8.75 carrier, keep the same max pinion diameter, move the new pinion teeth slightly rearward, lower ratios could be found. I don't think it would take much diameter reduction to get to 2.40. In my eyes it was possible. Just thinking out loud.

8 3/4 was pretty much out of production by the time the first gas crunch hit. 1974 was the year and the only pass car with an 8 3/4 was the E bodies, IIRC. Dunno about truck applications.

8-1/4 came as low as 2.29 IIRC. That was part of the reason they went to low gear sets in the trans.

I coulda swore I heard of a 2:45 available but it might have been for the 8&1/4

Highway gears....Nothing lower numerically than 2.76 for the 8 3/4.


I own a brand new OEM 2.94 set for the 489 case. They were going to go behind my stroker that never got built.

R.

No 2:45. Noted. EDIT on the other end I do have a set of 5.57's all ready and I have a 6 something R&P on the shelf (dont remember if they are 6:14's or 6:20 (8&3/4)

RapidRobert, I'm almost positive they made some 2.45 gears in the 9 1/4 axle. It seems like a set of those were in a rusty Cordoba I parted out decades back. I had an M body Grand Fury with the 2.2? gears in an 8 1/4 axle. It was a slug, so those were swapped for some 2.94 cogs!

Yeah I remember the 2:45 listed I just dont remember exactly what axle. that 2.2 was that for 70's EPA? mileage numbers!

2.45 were in the 8 1/4. I took the complete rear end out of a gold duster, way back in 1998, put it into my Duster360 that year and drove to Carlisle. Cruising at 70mph with 235/60/14 tires, 2.45 gears, the 360 was ticking over at 2650(ish) RPM. 22 mpg all day long, and the 360 torque, could always roast the right tire ! Have left that rear end in my Duster360 ever since ! . . . lowest numerical gear I have heard of for 8 3/4 is the 2.76 gear set. . . . good luck with your search . . .

That same combo in front of a 225 is horrible. Made that mistake when I upgraded by 72 Swinger to later discs and an 8 1/4. Looked at everything on the 8 1/4, except the ratio, before I pulled it from the donor. Only when I noticed my speedo was way off that I discovered my "find".

The one I had was in a 1983 (I believe??) Grand Fury. Oddly enough, that car was an ex-police car! It was not a police car intended for pursuit work, as it had the 318 2 bbl engine. It did not have all the other heavy duty features police cars typically carried either. The car was kind of a cross between a civilian Grand Fury and a Police Pursuit Grand Fury. According to the paper work that came with the car, it was last used by a state prison. I do not know if the prison ordered the car, or if it was given to the prison after being used by a police agency.

Swapping out the axle helped it a bit, but the car still did not run right. I tried tuning up the engine, but it still lacked power. Finally, I realized the engine had internal problems. I Pulled the 2.94 sure grip back out of it, along with a few other parts, and junked the rest!

Today, I wouldn't have so impulsively junked that car. It was the nicest driving M-body I owned.

Yeah I had an 83 cordoba 318 2bbl & it was the easiest starting vehicle I have even owned, shoulda kept it, hindsight. On the mileage regs with some thought I think it was COPO rather than the EPA

You could get the 2.45 gears in 1970 on a B Body, but in 8 1/4 rear end. It was part of the turnpike package . . . think it was 383 with cruise control and the 2.45 geared rear end . . .