Rear End Reccomendations

[Jsup]

OK, I'm upgrading my rear in April. I need some advice on what you guys think. My current rear is a 3.07 and the cam doesn't seem to like to operate at 1800-2000 RPMs, which is my highway speed, so I think I have to go up. I don't want to move up too much.

Grumpy, I'm looking forward to your input you told me a while ago, gears may be necessary.

I don't want to go up much, only about 200-300 RPMs.

Here's the spec:

1990

427 Small Block
240/242 cam HR .605 lift (total)
Centerline 108*
66* Overlap

700R4 trans
235 40R17 tires

I'm thinking 3.45s.

 

[mrvette]

OK, I'm upgrading my rear in April. I need some advice on what you guys think. My current rear is a 3.07 and the cam doesn't seem to like to operate at 1800-2000 RPMs, which is my highway speed, so I think I have to go up. I don't want to move up too much.

Grumpy, I'm looking forward to your input you told me a while ago, gears may be necessary.

I don't want to go up much, only about 200-300 RPMs.

Here's the spec:

1990

427 Small Block
240/242 cam HR .605 lift (total)
Centerline 108*
66* Overlap

700R4 trans
235 40R17 tires

I'm thinking 3.45s.

IMO, 355-370....and I would go to 50 series tires.....

 

[Jsup]

OK, I'm upgrading my rear in April. I need some advice on what you guys think. My current rear is a 3.07 and the cam doesn't seem to like to operate at 1800-2000 RPMs, which is my highway speed, so I think I have to go up. I don't want to move up too much.

Grumpy, I'm looking forward to your input you told me a while ago, gears may be necessary.

I don't want to go up much, only about 200-300 RPMs.

Here's the spec:

1990

427 Small Block
240/242 cam HR .605 lift (total)
Centerline 108*
66* Overlap

700R4 trans
235 40R17 tires

I'm thinking 3.45s.

IMO, 355-370....and I would go to 50 series tires.....

Why 50 series?

 

[big2bird]

I have 3.08's now in the 81 with a 700R. I will switch to 3.73 later this/next year. 3.55 would JUST be okay.

 

[Jsup]

I have 3.08's now in the 81 with a 700R. I will switch to 3.73 later this/next year. 3.55 would JUST be okay.

I'm afraid any higher would just SUCK on the highway.

 

[big2bird]

I have 3.08's now in the 81 with a 700R. I will switch to 3.73 later this/next year. 3.55 would JUST be okay.

I'm afraid any higher would just SUCK on the highway.

My truck has 3.73 and an OD tranny. Cruises just fine, and gets 21MPG highway with a small V-8

 

[mrvette]

I have 3.08's now in the 81 with a 700R. I will switch to 3.73 later this/next year. 3.55 would JUST be okay.

I'm afraid any higher would just SUCK on the highway.

Well, don't forget Jeff is in Ca. and that state is more vertical than horizontal, so for him, yeh, driving up walls is about 60% of the driving, so he needs the torque.....

I said 50 series 17" tires simply because the ride smoother and stand taller in the wheel wells, look better....same diameter as stock....when I put my '92 vette wheels on the car, the 40's is what they had then, when NITTO came out with the 275/50/17 it's what on the rear now for some 10? years now....

 

[AJ77]

I've got 3.70 gears and a 700R-4 behind an aftermarket TPI 383 stroker. @ 60 MPH I'm running 1800 RPM and get 22 MPG.

 

[mrvette]

I've got 3.70 gears and a 700R-4 behind an aftermarket TPI 383 stroker. @ 60 MPH I'm running 1800 RPM and get 22 MPG.

Well, that is where local conditions rule, and obvious intended use of the car....

everyone here in Florida, seems to cruise at 75+ quite regularly....sometimes I"m doing 90+ and everyone on my tail.....

 

[GTR1999]

I have 3.08's now in the 81 with a 700R. I will switch to 3.73 later this/next year. 3.55 would JUST be okay.

I'm afraid any higher would just SUCK on the highway.

My truck has 3.73 and an OD tranny. Cruises just fine, and gets 21MPG highway with a small V-8

I think it's the LA smog, it lubes the car to cut down on drag and increases MPG. Now that gas is going back up I'm thinking of opening a chain of Air Lube stations, kind of like a car wash only we'll spray the cars with oil to increase MPG,what do you think? You want to give up playing with electrons and run the So Ca chain!

 

[big2bird]

I have 3.08's now in the 81 with a 700R. I will switch to 3.73 later this/next year. 3.55 would JUST be okay.

I'm afraid any higher would just SUCK on the highway.

My truck has 3.73 and an OD tranny. Cruises just fine, and gets 21MPG highway with a small V-8

I think it's the LA smog, it lubes the car to cut down on drag and increases MPG. Now that gas is going back up I'm thinking of opening a chain of Air Lube stations, kind of like a car wash only we'll spray the cars with oil to increase MPG,what do you think? You want to give up playing with electrons and run the So Ca chain!

We do alot of drafting.:rofl:

 

[BRUTAL64]

I have 3.08's now in the 81 with a 700R. I will switch to 3.73 later this/next year. 3.55 would JUST be okay.

I'm afraid any higher would just SUCK on the highway.

My truck has 3.73 and an OD tranny. Cruises just fine, and gets 21MPG highway with a small V-8

I think it's the LA smog, it lubes the car to cut down on drag and increases MPG. Now that gas is going back up I'm thinking of opening a chain of Air Lube stations, kind of like a car wash only we'll spray the cars with oil to increase MPG,what do you think? You want to give up playing with electrons and run the So Ca chain!

We do alot of drafting.:rofl:

Yes we do. But at 5 mph it does not do much good.:skeptic:

 

[69autoXr]

235 40R17 tires

Surely this is not correct is it?

 

[Jsup]

I've got 3.70 gears and a 700R-4 behind an aftermarket TPI 383 stroker. @ 60 MPH I'm running 1800 RPM and get 22 MPG.

Well, that is where local conditions rule, and obvious intended use of the car....

everyone here in Florida, seems to cruise at 75+ quite regularly....sometimes I"m doing 90+ and everyone on my tail.....

I cruise at 80.....I don't want the car spinning that high.

 

[big2bird]

I've got 3.70 gears and a 700R-4 behind an aftermarket TPI 383 stroker. @ 60 MPH I'm running 1800 RPM and get 22 MPG.

Well, that is where local conditions rule, and obvious intended use of the car....

everyone here in Florida, seems to cruise at 75+ quite regularly....sometimes I"m doing 90+ and everyone on my tail.....

I cruise at 80.....I don't want the car spinning that high.

Then it sounds like 3.55 is the right choice for you. You certainly have the engine to pull it with.

 

[Jsup]

I've got 3.70 gears and a 700R-4 behind an aftermarket TPI 383 stroker. @ 60 MPH I'm running 1800 RPM and get 22 MPG.

Well, that is where local conditions rule, and obvious intended use of the car....

everyone here in Florida, seems to cruise at 75+ quite regularly....sometimes I"m doing 90+ and everyone on my tail.....

I cruise at 80.....I don't want the car spinning that high.

Then it sounds like 3.55 is the right choice for you. You certainly have the engine to pull it with.

That's what I'm thinking.