Help! In search of stock gears...

So when I bought my jeep it had a T-18 4 Speed Transmission w/6:32 1st gear and Dana 44 Rear W/3.73 Gears/ 30 Spline Axles which means I was never able to get this thing to go past 50 mph. I also broke the steering column on it last time I was out on southern so its just been sitting at my apt complex but I finally got it towed to my mechanic and am going to have him get it running good again.. I am going to add power steering, power brakes and want to put the stock gears on it so I can actually take this thing on the highway. The jeep is a 1972 CJ5 I am not really sure where to look for stock gears for this thing or how much they will cost. My mechanic said I am looking at about 1000 for the gears alone so he told me to try looking online and he will install them for me. So any help would be greatly appreciated smile.gif

 

Tell you the truth I couldnt tell you I always thought it was the gear ratio? Since the gear ratio is set really low?? This is the list of stuff that I bought it with...

AMC 360 v-8 (75,000 Miles)
-T-18 4 Speed Transmission w/6:32 1st gear (Granny)
-New Paint
-New Clutch
-Dana 44 Rear W/3.73 Gears/ 30 Spline Axles
-Detroit Locker (Rear) W/ anti-spin
-Model 30 front W/ Loc-rite Locker
-Headman Headers
-3” exhaust W/ Dynamax racing mufflers
-6” total Lift (2” body / 4” suspension)
-33 X 12.50 X 15 Procomp Mud Terrains
-Aluminum wheels
- 6 states CV rear drive shaft

 

Any suggestions on what it might be? The jeep has a ton of torque and power and is a beast off road but once it hits pavement it hates it.. it starts shaking like hell once you hit 50 and it also sounds and feels like it doesnt want to go anymore? I put new rancho shocks thinking it was the suspension? I also swapped out the tires cause i bought it with 38's and i swapped em for 33's I dont know what else to swap out?

 

My CJ with a 258 does 70 with 31s and 3.73 gears. The only time I had any problem was when the rear main leaked oil all over the clutch assembly causing slippage. Another truck I had wouldn't get up to speed b/c the weights for the spark advance were siezed (rusted) and wouldn't open up. I check the simple stuff 1st before I start throwing time and money at fixes.
Good luck.

 

Does your Jeep have a tachometer on it? If so, how many RPM's are you turning at 50 MPH? I hate like hell to make this stupid suggestion but you're not in low range, are you? Some of the D20 Tcases actually have a 2wd low position.

P.S. My 80 CJ-5 with 258 L6, 4.10's and 32" BFG MT's will cruise at 50 effortlessly.

 

The stock gear ratios in a '72 will let you go 70-80 mph easily. You don't even need a paved road to go 50. A '72 CJ with a 360 and 3.73s should be able to do 85-90 easily, if you dare.

Also, the 4-speed transmission does nothing to the top speed. Most transmissions connect straight through in top gear, and have no effect on the top speed. The T-18 is irrelevant to your top speed.

Pull the differential cover off and read the tooth ratio from the gears themselves. This will be stamped into the edge of the ring gear. Divide the two mumners, ie 39 11 is 39/11 = 3.54:1. Unlikely you'll find anything but confirmation of the 3.73 ratio, but a check will help your piece of mind.

Also, Jeeps are noisy. Uninitiated drivers might not understand how noisy. Tires, gears, engine, exhaust all make noise, and there's no insulation between you and them. The fan also makes a lot of noise. If you have an aftermarket fan (ie not the stock fan and fan clutch) it could be very loud. I used a flexalite for a while, and the Jeep sounded like you were standing behind a jet engine...

You can calculate what your engine speed is from the tire height and speed reading. Realize that your speedometer will be affected by the tire height too - if your speedo reads 50 and you're keeping up with traffic, you're not really going 50.

A tachometer is a good idea if you still feel nervous.

Shaking like hell? What do you mean? Describe better please.

 

I agree with what's already said. I'd also check and make sure it isn't in 4 wd as you said you hit pavement and it starts shaking badly. This can cause driveline bind and create an issue similar to what you are experiencing. According to my chart with 33" tires and 3.73 gears you should only be turning 2279 RPM at 60 mph. You've got another issue somewhere and if your mechanic can't figure it out and is simply blaming it on the gear ratio, get another mechanic. Nickmil

 

Another thought - if your Jeep came with a 304 and was changed to a 360, it's possible the PO reused the 304 flywheel. This would be bad. The 304, 360 and 401 are externally balanced (aka Detroit balance), and all have their own flywheels that are balanced differently. You must use a 360 flywheel with a 360. The 304 flywheel will bolt on, but it will not balance the engine correctly.

 

If it starts shaking at 50 i would check out your tire balance. With everything right you should be able to go well beyond legal speeds with no vibes, just a lot of noise.

 

I was running "45mph" the other day, and passing cars- 33-12.50s will do that

 

If the flywheel is wrong, it will vibrate if you rev the engine with the vehicle at a stand still and transmission in neutral.

 

Its not that stupid. I knowingly drove in the street in low and managed to get up into the 40's speed wise. The motor started to get a little warm, and it was using fuel at an alarming rate, but it made it up there.

My 72 with 3.73's can get to 50 no prob in high range, but the steering makes you wish you weren't going that fast.

 

The noise is normal on the jeep its noisy but its cause of the v8 engine and of course it rattles like everyother jeep but what i meant by it shakes like hell is its hard to control the steering wheel jerks from left to right... i had a friend drive on the side of me and tell me how fast i was going at top speed as fast as the jeep could go without scaring the hell out of me and top speed i got it to was 55. The funny thing was at that speed my tach was only at 3200 rpms? in 4th gear.. My mechanic hasn't started working on it but I till keep everyone updated.. when i explained the problem to him he said it was probably the gears so thats what made me assume that. btw its not in 4 wheel drive either i have taken my jeep in 4 wheel drive on dry pavement and there is a huge difference.

 

Sounds to me like an alignment/tire balance problem.

 

I'd suggest -

Check the actual ratio of the gears. Look at the tooth count stamped into the ring gear.

Measure the caster. Any place that does front end alignment can do this for you. Toe-in is also important. I'd also check that your wheels are balanced. The gearing has nothing to do with the shaking problem.

The only way you could be going 55 mph at 3200 rpm with 33" diameter tires is of the gears are 5.38:1, not 3.73. Something is not right in this story... tach, speed, gear ratio... something.

 

Did not see this before. But check for a bent driveshaft or pull them and have them checked for balance.

 

Steering jerking around sounds like really bad tire, bent wheel, bent axle, spindle ready to fall off, hub ready to fall off, steering linkage ready to fall off, steering box ready to fall off. Shouldn't be too hard to track down if you troubleshoot based on the actual symptoms. It doesn't sound speed related at all, and it sure doesn't sound like gears, tranny, engine, etc.

 

Excelent suggestion. If you have some lift in your Jeep it is easy, especially in a CJ-5 to end up with bad rear driveline vibrations/shakes, even at relatively low speeds. I had to get a CV shaft to fix it.
Also confirm the gear ratio for your own knowledge, but I doubt the gears are the reason for your troubles.