Rear End Reccomendations

Jsup

Jsup

Well-known member
Joined
Oct 31, 2008
Messages
812
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.
 
Jsup said:
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.
Click to expand...

IMO, 355-370....and I would go to 50 series tires.....
 
mrvette said:
Jsup said:
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.
Click to expand...

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


Why 50 series?
 
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 said:
big2bird said:
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.
Click to expand...

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

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....
 
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.
 
AJ77 said:
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.
Click to expand...

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.....
 
big2bird said:
Jsup said:
big2bird said:
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.
Click to expand...

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

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

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!
 
GTR1999 said:
big2bird said:
Jsup said:
big2bird said:
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.
Click to expand...

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

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

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!
Click to expand...

We do alot of drafting.:rofl:
 
big2bird said:
GTR1999 said:
big2bird said:
Jsup said:
big2bird said:
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.
Click to expand...

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

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

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!
Click to expand...

We do alot of drafting.:rofl:
Click to expand...

Yes we do. But at 5 mph it does not do much good.:skeptic:
 
mrvette said:
AJ77 said:
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.
Click to expand...

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.....
Click to expand...

I cruise at 80.....I don't want the car spinning that high.
 
Jsup said:
mrvette said:
AJ77 said:
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.
Click to expand...

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.....
Click to expand...

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

Then it sounds like 3.55 is the right choice for you. You certainly have the engine to pull it with.
 
big2bird said:
Jsup said:
mrvette said:
AJ77 said:
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.
Click to expand...

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.....
Click to expand...

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

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

That's what I'm thinking.
 
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