need a higher top speed

Unless you get an Overdrive tranny, it wont improve your top speed. Most transmissions are 1-1 in last gear, unless again, you get one with an Overdrive ...

They do make "add-on" overdrives for some transmissions. Not sure about yours particularly though...

Differential gearing may be better option to change if you want better freeway speed... :cool:

Others may have another idea for you though...

:chug:

~ JR
 
If you already have Overdrive swapping trannies wont get you a higher top end. Sounds like you will need to change the gearing in your differentials.
 
1955jeepwillys said:
I currently have a chevy 327 with a T-90 Transmission mated to a D18 with Overdrive .
Click to expand...

:wtf: Apparently I skimmed right over that... Sorry...

Advice still same, and as Ken pointed out too...

Do you know what gear ratio you are currently running, and what tire size you are running?

Those will help... Sounds like your gearing may be too low for top speed, though probably better for crawling / off road.

There's a balance to be had there.

:chug:

~ JR
 
Gears for sure.

Besides they could be cheaper. Well as long as you're in there - lockers. Forget the cheaper now.
 
haha my jeep is maxed out keeping up with people on the by-pass (45mph) :laugh:
 
1955jeepwillys said:
I currently have a chevy 327 with a T-90 Transmission mated to a D18 with Overdrive .
Click to expand...


I had that exact same drivetrain in my very first CJ, a 1947 CJ2a . That little thing kept up with everything I wanted it to, but then again I was a HS kid and didn't care about things like gear whine, fuel mileage, or expecting the rig to last for any length of time!
Seems like gears are your only answer, weather you change the current gears or throw a set of newer axles under there with the gearing you want. Then you can have disk brakes as well...
 
You could pop on a couple size bigger tires which will reduce your final drive ratio and allow a top higher top speed and lower cruising RPM? With that motor power shouldn't be an issue. I don't know what you Jeep has for tires but they usually can get away with two sizes larger than stock before a lift is needed.
 
what is your axle ratio now??:D
 
Im not sure what axle ratio it has. How do I check it if there is no tag on the diff? I have 29in tires now with a 2.5in bds lift. Do you think my speed will change much with 32in tires?
 
Jack-up the rear of the Jeep. Block the front wheels and place the Transmission or Transfer Case in neutral.

Make note or mark a wheel and the drive shaft.

Start to rotate a wheel by hand, if the other rear wheel rotates in the same direction (this means you have a Limited slip or locking diff) - rotate the wheel one time and count the drive shaft revolutions.

If the other rear wheel turns in the opposite direction (this means you have an open diff) - rotate the wheel two times and count the drive shaft revolutions.

Your ratio is determined by the number of drive shaft revolutions.
Example - if the shaft rotates about 3 3/4 turns you have a 3.73 diff gear ratio.
 
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