where can i find a overdrive

i would love to make my 75 cj5 with the straight 258 more highway worthy without losing any of its four weel drive capability. so i was thinking of putting in a overdrive on my t-14 tranny. although i am not sure were to get them or how much they cost. i heard they can be just a bolt on operation without any modification. what do you think? and do you have any info

 

http://www.hermtheoverdriveguy.com/

Don't buy an ebaY unit...you will pay as much as what Herm can build for you fresh. Contact him regarding your specifics and he will suggest the solution for you.

 

What Transfercase do you have? I thought the intermediates came with a Dana 20 which does not have an overdriver option, only the Dana 18 did.

 

That's correct. I believe if you want an overdrive, you'll have to put in a tranny with an overdrive. Or swap out the D20 for a D18 Tcase and put in an offset D44 rear axle. Not really worth the expence.

 

The T-14 is not that low geared. A 4 speed with overdrive from a newer jeep will probalby be the best way to go. You may even be able to get one that has a Dana 300 T-case on it. Same high range as the 20 but better low range gearing.

 

Even with the lowest factory gears (4.27s) the Intermediate CJs are fine on the highway. Just some friendly advice - get some more info about gearing and engine speeds before you decide that you need an overdrive. Even with the stock sized tires (29" tall) and the optional low axle ratio (4.27s) you are well within the comfortable RPM range for the 258. Most of these Jeeps were delivered with 3.73s, in which case the 258 is loafing on the highway (comparatively speaking).

It's also correct that the Warn/Saturn overdrive that can be used on pre-72 Jeeps will not fit on your 75.

The 4-speeds from later Jeeps (SR-4, T-4, T-176) are not overdrive transmissions. The T-5 is, but it would be a downgrade from your T-14.

More advice - make sure everything is in good condition and drive it, but don't expect to keep up with fast traffic on the highway. Taller tires will help your highway RPMs a little, but if you already have 31s or 33s, you should be fine on the highway.

Welcome from Boston!

 

i didnt even know that their was not an option for an overdrive for d20, and i dont really have the money for tranny, tcase and rear axle. i need to change out the oil iin the differentials but other than that everything else is lubed and in good condition as far as mechanically goes.
on flat land i can get it up to about 65mph give or take but it seems like its having a hard time with that speed i dont know if thats just a jeep thing or do i just expect to much as far as speed from my jeep. "Taller tires will help your highway RPMs a little, but if you already have 31s or 33s, you should be fine on the highway".
i have 31x10 tires. do you have any other suggestions for better speed on the freeway or is this as good as it gets without swaping out anything?
thanks for all your suggestions

 

What's your axle ratio? You shouldn't be limited by the throttle - a 258 makes plenty of power for a light vehicle like a CJ. A Jeep does make a lot of noise compared to passenger car, no insulation between the engine and the cabin, gear noise, tire noise...

Have you checked the engine compression? Does your engine use any oil? If you don't have any power, and the drivetrain is ok, then I'd investigate the condition of the engine a little more. I have the same engine as you do in my pickup, and I can go 70-75 with no trouble. Might be something simple, like carburetoin or timing.

 

what would be the max rpm's on a 258 on a 74 cj5 w/ 4:27 and 33" tires? My max is about 3000 rpm and if I go faster (only exceeding 65 if going downhill) I think the engine will blow up.

 

There's a calculator here: http://www.novak-adapt.com/knowledge/gearing.htm

3000 rpm should be 69 mph. Modern engines like the 258 can go 3000-4000 rpm easily, and for long periods. 3260 at 75 - no problem! Note that "33" tires usually aren't really that tall, but revs of 3000-3500 should be easy for that engine. Realize that, if you are turning 3000 and you have 33" tall tires, you are going 69 mph, regardless of what the speedo says.

 

i dont know a whole lot of anything about gear ratios all i know is i got a stock d44 axle in the rear and 30 in the front.
i have not checked engine compression, and it dosnt burn oil. i checked the timing just yesterday, in fact and it was supprisingly pretty good.
the carburater (just a single barrel) needs a new choke, could that be an issue? i know it is starting it up on cold mornings but how about on the freeway?
"no insulation between the engine and the cabin, gear noise, tire noise..."
and then again maybe i am just not use to hearing a vehilce run at such high rpms. i suppose anything is possible.

 

If the choke does not open fully when warm, that could severely limit performance.

The axles came with tags under the bolts that lists the Jeep PN and ratio. The two stock ratios were 3.73:1 and 4.27:1. If you are lucky, the tags are still there. There are other ways to determine the axle gear ratio, either by reading the numbers stamped into the ring gear, or by turning the driveshaft and counting the number of rotations to the wheels.

It's not that high. I drove my '73 CJ up Cajon Pass in CA at 80 mph, full throttle all the way. I would regularly drive to work at 4AM at 70-75. Sounds like its running fast, but it's not.