starting the change

[country tough cj5]

I have a plain jane original 1979 CJ5 . Love the jeep and enjoy driving it until I hit the highway. Runs high at 60mph. Can anyone give any incite on what the best mods are for regearing my jeep. It has the AMC 258 i6 / 4.2l inline 6 with manual 3speed tranni. I don't really know wear to start or best place to buy parts on a budget. Any help is appriciated. Thanks.

 

[Torxhead]

If you want to slow down the rpms on the freeway, larger diameter tires is one way to do it. That will slow down the bottom end down though. The main thing is to figure out just want you want to do with it. Going above 60 mph is a bit scary, not to mention stopping it in a hurry.

 

[Old Dog]

with so many people wanting to gear the other way there should be lots of used gears or whole axle assembly's out there. Start by finding out what ratio you have now.
Torxhead has another way if you can fit bigger tires.

 

[Saddle Tramp]

The mods you select depend a lot with what you plan to do with your jeep. There is a certain “cool factor” these days with a “Plain Jane” rig that hasn’t been butchered. As far as high rpm at highway speeds the only three options I see are, larger tires, change the Transmission to one with an Overdrive and/or put taller (numerically lower) gears in the differentials.

There was only one Transmission with an Overdrive , the T-5 , which was used in a CJ (1982 to 1986) and it is only a light duty Transmission . The good thing about a T-5 is it is set up for a Dana 300 Transfer Case , the best of the best ever used in CJs. The Dana 300 is a strong box with a relative low, low gear compared to the Dana 20 that’s stock in a 1979 CJ.

Perhaps the gearing in the differentials has been change causing excessive rpm? Something to check but again if you put too tall of gears in then the motor will have trouble holding top gear on the road.

More modern transmissions used in Wranglers and other vehicles can be adapted to work but in a CJ5 one has to be mindful of how short the rear drive line becomes after the swap or there will be a real problem with vibration and U-joint failure.

60 mph is plenty fast is a CJ5 but with a V8, from person experience, they will fly down the road at 80 just make sure your life insurance premium is paid up as your family is going to need it to bury you.