Transmission help/ advise help

[countrylegend]

Hello all,
I haven't owned my '83 CJ7 but a couple of months, and after this past 4th of July weekend am having to do a 350 swap earlier than I wanted to. (Dipstick blew out and blew 4 quarts of oil out going down highway)

After doing a little of google research I think I'm gonna put the SM465 Muncie in my jeep and go back with my Dana 300 . I also considered the ax15, but liked the 465 because of the granny lo and how tough it is. The only thing I'm not sure is how does the 465 drive down the road?

I bought my jeep as a toy and weekend driver to the store or 100 mile trip home or beach ect. Right now I do lite off roading(sand,mud, crawling), but interested in getting more into crawling. I know the 465 is good for that, just wondering if I'm gonna hate highway driving in it?

Any help, advice, or suggestions is greatly appreciated.

Thank you

 

[hole]

First off, Welcome . Since you have an 83, then you probably have either a T-4 or T-5 Transmission . If you have a T-4 , you shouldn't see much difference on the highway, but if you have a T-5 you'll notice it. What gears are you running?

 

[countrylegend]

I assume the T-5 is the 5 speed? If so that's what I have in it now. As far as what gears I have, I'm not sure ? I just know they are Yukon that's what the previos owner told me. Sorry I know that's not much help, and I'm a newbie too so that's not much help either.

 

[countrylegend]

Anybody have this tranny in their jeep and do much highway driving with it?

 

[Sam5038]

I have one. I'm running 4:27 gears and it's a great Transmission . I'm using it behind my 4.3ltr Vortec TBI V-6. I never use first gear on the street and fourth gear is 1 to 1. Also. This is a large Transmission . It will hold one gallon of gear oil and it weighs 175 lbs empty.

 

[countrylegend]

Yeah I know this is a heavy beast of a Transmission . From what I've read it will handle just about anything you throw at it.

So as far as gears go what would be a good combo with this tranny? I could possibly have them in it already?? Not sure what's in it now, but I know they aren't stock.

 

[GatorBate]

Here are links to a couple of gear ratio calculators. You can play around with them and get an idea what different combination of gearing will do for you.

Gear Ratio Calculator

Gear Ratio Calculator

 

[JR74CJ5]

if you haven't changed and inspected fluid / gears in front and rear end, the safest bet is to do so. You can then look for the stamped numbers on the gear-set or count the teeth and get your gear ratio you currently have.

you can do this without breaking the seal on the diffs by counting the revolutions of the drive shaft in relation the the tires as well.

There are a few write ups on the subject that will help you.

The gear calculator will help you figure out what to swap to if you need to.

The SM465 is 1:1 in the final gear (most are) but your 5 speed probably has a over-drive, which you will notice loosing on the freeway as you wont have that extra gear to cruise in for better mileage / lower cruising RPM.

the "best gear combo" is up to you.. the tire size you wish to run, and speeds you wish to cruise at all play a factor in the decision making process.

I'd say you first place to start will be seeing what gears you currently have...


~ Jr

 

[Petescj]

If you had stock gears in there with 37 inch tires youd know it. I grabbed the SM420 Transmission for my Limited build which is almost the same. Alot of things have been covered already. It has a great 1st gear for crawling that you never use on the pavement. Every stock Cj Transmission from this era has a final ratio of 1 to 1 except the T-5 . It has an Overdrive but the ratio escapes me right now. With that being said that would mean the only Cj that was ever decent on the highway would be ones equipped with a T-5 .

I had a 78 CJ5 and a T-150 3spd. with 4.10s that would purr along at 70 mph no problem. Id love to know what gear ratio your running in those axles. Everything is relative when it comes to this. I imagine anything that worked for thr T-5 will be fine with your SM465

Yeah I know this is a heavy beast of a Transmission . From what I've read it will handle just about anything you throw at it.

So as far as gears go what would be a good combo with this tranny? I could possibly have them in it already?? Not sure what's in it now, but I know they aren't stock.

 

[countrylegend]

Changing all fluids except in the tranny is one of the first things I had done. I'll have to try the tire and drive shaft trick this weekend if I'm not working.

To be honest I could run 60-70 down the highway in 5th gear no problems.

 

[Torxhead]

If you are considering switching over to a non-Overdrive Transmission , why not spend some time without using the Overdrive ? With the heavy duty compound low in those transmissions, they are mostly non-synchro in the first gear. So you have to come to practically a full stop to get it in, and they are too low for most street driving. So second gear is a lot easier to use, they are around the 3 to 1 ratio, and your second gear is 2.37 to 1 to give you an idea. They were designed for heavy duty trucks when carrying big loads, with that V8 you will probably be in good shape though, and consider gas mileage and distance to empty. Yes, they are awsome for crawling, especially with 4 to 1 Transfer Case gears

 

[countrylegend]

I'm sure it's not apples to apples, but my Cummins has the NV5600. I only use first when I'm loaded down with my 5th wheel, or just easing around tight spots at work. When my jeep was drivable I drove it some by not putting it in 5th/O.D. I didn't buy my jeep for the gas mileage (but was surprised by it getting 14mpg) so losing O.D. I don't think is gonna kill me. Also when I took my jeep into our rocks to mess around 1st gear that's in it now was a little to high.

 

[countrylegend]

I just want to say thank you to everybody that gave advice and input. I really appreciate it :rock: