Chrysler rear end.

[RockJustRock]

On an 8 3/4 the easiest way is to get a complete carrier assembly from a salvage yard. But....

I am not bullish on ratio changes for a street car. You ONLY get a little more at the beginning of first gear and higher RPM range at cruise.

As I've previously said my dream mod for your car would be electronic stack injection. It would look like something the guy that built it wanted and drive great. Barring that I'd say throttle body fuel injectors and electronic ignition either way.

[fatguyzinc]

check your snout casting number, last 3 should be either 741, 742, or 489--there are differences in pinion
shaft diameter, so make sure before you order. going up just 1 ratio seems non-sensical to me, but hey--
your car/your money.

"usually" 3.73 is a good balance on a street car between all out acceleration and cruise speed on freeway.
want more acceleration try 4.10, more freeway flyer try 3.55.....

and an 8.75 is a really REALLY good rear axle--quick comparison to a 9" ford/12 bolt GM has the 8.75 winning in my
book because ALL 8.75 were 30 spline, ALL had nodular centers, ALL had bolt on bearings/no "C" clips, etc...

but unless i owned one like you already do, for the money it cost to buy/build, id just do a dana 60 or a corporate 14, hah hah...

[anotheridiot]

Thanks guys I think that's what I'll do. $275 plus some labor for the install as I've never been inside a rear end. The 3.55 should be just enough. The old Hemi doesn't get good gas mileage anyway so just a little more punch.

just not to go from bad to terrible. our fourth gear cruise at 35 with the 4:11 is 2550. They said dropping to the 3:55 would take it to 2160. Still not sure it will be enough.

Pretty sure there will be an assembly kit, new bearings, shims, crush sleeves that would add another 100.

[kolsen911]

Thanks guys I think that's what I'll do. $275 plus some labor for the install as I've never been inside a rear end. The 3.55 should be just enough. The old Hemi doesn't get good gas mileage anyway so just a little more punch.

[anotheridiot]

Got a couple calculators from Quick performance to see if it could answer anything. We are at a 4:11 and wanting to go the other direction

https://www.blocklayer.com/rpm-gear.aspx

https://weddleindustries.com/gear-calculator

[squirrel]

3.23 is what you probably have now, 3.55 was also available.

https://www.summitracing.com/search/department/transmission-drivetrain/part-type/ring-and-pinion-gears/axle-model/chrysler-8-75-in-489-case/ring-and-pinion-ratio/3-55-1?N=ring-and-pinion-ratio%3A3-55-1

[kolsen911]

Some of you may know I'm the one with the Hemi/Vette. While thinking about a little boost in the performance of this combination, which is basically a stock 57 392 Hemi @about 325 hp, I got to thinking of just a change in the rear axle ratio. While up on my 4 post lift I jacked her up so I could spin the rear and I think the axle is about a 3.25.

It is a 8.75" Chrysler rear (#2881489) and approx 3.25 ratio. Since I'm a Chevy/foreign car guy, I'm asking you guys who know, is there something like a 3:55 rear end I could get for this axle??

I figure that little boost would be just enough for this car, which is just a cruiser, to give it a little more jump rather than pulling the engine and going that route.