My truck has a 400/700r4 and 2.74 rear..which rear to get for economy & peformance

[erikgto]

Hi guys,

Found out that my '86 still has it's original 2.73 peg leg rear.
I will be running 385/40 or 295/40R20's.
Clearly the 2.74 is purely an economy gear and will have the 400 sbc lugging around.

I want to keep economy and relative low highway RPMs in mind, but I do think something like a 3.42 would be way better for performance without hurting my fuel economy.

What would you do, buy a complete used rear (sight unseen over internet) or swap ring and pinion?

[Jonboy]

I would swap to a 3.42 ring and pinion. Shipping would be a lot easier, and you would probably come out better in the long run.

[Clyde65]

3.42 or 3.73

[benoit454]

x2 at least 3.42 maybe as far as 4.10's if you have a tall tire since you'll have od, but really 3.73 would help give you fuel mileage. If you want more fuel mileage then power do 3.08.

[Keith Seymore]

3.42 is usually my "default" setting.

By having an overdrive in this case, 3.73 might give you a bit more pep.

K

[Greenlee]

I did this on my 76' Silverado. I went to Pick-a-Part and pulled one with 3.73's. It was like a different truck with 3.73's.

I thought this was easier and cheaper than swapping out the gears, however, since you are in The Netherlands having a complete rear end shipped to you might not be that easy.

[jchav62]

Since you have such a high gear ratio out back, just use Drive(3rd), and save the overdrive for that flats and downhills...

[erikgto]

Thanks for the response

I guess I'll be on the look for a 3.42 set.
With gasprices right around $ 8,- a gallon around here I'm leaning a bit more towards better mileage than quicker acceleration.
Might take the plunge and go for a posi at the same time.

If I get the urge to play I can allways get in my '71 Pontiac and go

[benoit454]

yea you wouldn't need od with them gears but I would agree you need more pep for sure. I usually like alot taller gear for torque and take off and od helps out with rpm's.

[Clyde65]

is the truck you r play toy? do you live in the city, do you drive the highway alot?

If your playtoy, or you live in the city, then 3.73 is the way to go...

If your DD or you drive the highway alot, then 3.42 would be best

[N2TRUX]

My experience has been with an OD transmission, a 3.42 is good for one MPG over a 3.73. The fun factor goes up considerably, but the 3.42 is a good compromise.

Keep in mind, you probably have a 3 series carrier, so a 3.73 won't fit unless you order a set specifically for the 3 series.