Overdrive ???

Are the warn and husky OD's specifically designed for the 18s or can they be put on a d20? I've also got a spicer18 from a scout, is that the same thing as Dana18? And if so, could i put an overdrive on that and mate that with my t14?

 

they only work on a dana 18. dana/spicer 18 is the same thing. if you swap your 20 out for an 18, you can use an OD, but you'd have to change your rear axle to be compatible with a dana 18. the dana 18 transfer case uses an offset rear differential, while the dana 20 uses a center rear differential.

 

hmm................ Lets say i swap out for a d18 and an offset rear. Would it be worth it just for the overdrive. How is the early diff compared to the intermidiate.

 

IMHO the OD is well worth it, if you plan on doing any street driving. I can cruise the freeway at 65mph and tack around 2600 rpm with 4:88 gears. Without the OD I would be lucky to make it to 55mph and hold the engine together. Just my $.02

 

The stock axle ratios for the '73 are 3.73 (std) or 4.27 (opt). Either of those ratios are FINE on the street. You don't need an overdrive.

Jeeps make a lot of engine noise, tire noise and gear noise. Even with the short OEM tires, you can travel at highway speeds EASILY. How tall are your tires and how fast do you want to go?

 

I used to drive in the fast lane on the CA freeways all the time in my '73 with 4.27s and 31s. Even with the stock H78-15 tires, it was fine on the highway. I'd never win a race with a CHP cruiser, but it went as fast as was safe (faster really).

If the Jeep had 4.27s and a D18, you might want an overdrive, but I'd think it might not change the mileage that much. With a T-14 it would be helpful because it would give you a more usable passing gear. D18s are freakin' noisy too, so you might want to drop the revs to make a little less gear noise.

 

While you can't use a Warn Style OD with a 20, you might be able to use a Rancho (Borg-Warner) Style OD. It's 2WD only and in a CJ your going to have a real short rear driveline though, probably need CV joints in the driveshaft. It's much more suitable for wagons and pickups.