Available Ratios in 1962 CJ-5's for Dana 44 Limited Slip Differentials

Gents,

I have determined that my Dana 44 rear diff is not the standard 5.38:1 ratio that I guess was popular back then. It is more like a 4.25:1 or something close to number. Do any of you know what ratios may have been available then? I asked this in one of my posts, but it was far down the list and not a general question, so I thought I would toss it out here and see what I get in return. As usual, thanks in advance for any help.

 

4.27 was an option at some point but I didn't think it was as early as '62.

 

What is the difference in the gear ratios ? one makes the jeep go faster ?

 

Gear ratios are a trade off. They maximize the available power for the intended usage. Lower numeric numbers give more torque at the rear wheels in any gear while higher numbers allow for more speed in any gear. And there are diminishing returns both directions and tire height plays a big role in what works best.

 

I think what Mike intended to say was.........................Higher numeric numbers ( like 4.88's - 5.38's ) are lower ratios and will apply more torque. While lower numeric numbers ( like 3.0 - 3.73 ) are gears that are more for higher Speed. Confusing Yes............but you would not put a 4.88 gear in your Jeep to go fast on the freeway.

 

5.38 was the only CJ ratio ever available prior to early 1963 model year ........
http://cj3b.info/Photos/Tech/ServiceBulletins/SB601AxleRatio.JPG

 

5.38 gears and 35" tires. When I am doing 2500 rpm my speedo says something like 40~42 but the calculations say I am doing 48. I was looking hard at an overdrive, but with 35" tires I just don't need it unless I am going on the highway. Thats not going to happen.

 

Look at the tooth count numbers stamped into the ring gear. "47 11" = 47/11 = 4.27. I think that's right for a D44 with 4.27s.

Will the 4.27s make the Jeep go faster? Maybe, a little. The F134 is either power or RPM limited in the CJ-5. Recall that power = RPM * torque * (some conversion constant), so the faster the engine spins, the more power it makes. UNTIL you reach the point where the torque curve is falling off faster than the RPM is increasing. With 5.38s, you are topping out at around 55-60 mph. At this speed, the drag from the air (proportional to velocity squared) is increasing faster than the power is increasing with RPM. With 5.38s the engine spins faster giving more power, but the engine is really straining at the end of its torque curve. With 4.27s its probably not much different, but instead the Jeep just won't go any faster because the lower power at lower engine speed equals the drag.

I expect that if you went to, say 3.73 gears, your top speed would decrease to below 55 because you'd hit that power equals drag barrier at a lower speed.

 

3300 with 4.88s on 33s is 66 mph.

 

Yes other differential ratios were around long before 11/1962 but not for the CJ's.
The MB, GPW was 4.88.
Stock components were specified by the service standards for each particular model and vintage.
No CJ never had a factory designated differential ratio option prior to 11/1962.
All CJ's were 5.38 ratio 39/8.
The 5.38 ratio was a carryover from the 1945 Agri-Jeep (plow Jeep).
Even though the Hurricane is more powerfull than the Go-Devil, the differential ratio was not changed in 1953.

Look at the tooth count numbers stamped into the ring gear. "47 11" = 47/11 = 4.27. I think that's right for a D44 with 4.27s.

Will the 4.27s make the Jeep go faster? Maybe, a little. The F134 is either power or RPM limited in the CJ-5. Recall that power = RPM * torque * (some conversion constant), so the faster the engine spins, the more power it makes. UNTIL you reach the point where the torque curve is falling off faster than the RPM is increasing. With 5.38s, you are topping out at around 55-60 mph. At this speed, the drag from the air (proportional to velocity squared) is increasing faster than the power is increasing with RPM. With 5.38s the engine spins faster giving more power, but the engine is really straining at the end of its torque curve. With 4.27s its probably not much different, but instead the Jeep just won't go any faster because the lower power at lower engine speed equals the drag.
I expect that if you went to, say 3.73 gears, your top speed would decrease to below 55 because you'd hit that power equals drag barrier at a lower speed.

Timgr is basically right on.
Yes 4.27 always = 47 / 11 regardless of vintage.

4.27 differential ratio was Jeeps early attempt to get more speed from the Hurricane.
I have operated the Hurricane under various conditions.
I have installed and operated a stock CJ with various drive ratios with O.D. installed.
The absolute best configuration for the Hurricane is 5.38 and O.D.
For typical driving the Hurricane engine (in excellent condition) will actually be slower with 4.88 and O.D. than 5.38 plus O.D.
If you can't afford the O.D. unit then 4.27 allows a bit more speed than 5.38 without.
Insufficient torque at a normal operating RPM is the key problem.
The O.D. unit was not designated as JEEP APPROVED SPECVIAL EQUIPMENT until September of 1964.

 

Now there is a split and a divider for 4 wheel drive . My 95 wangler with a 4cyl. would tow a 21 ft cuddy cabin out of the water in 4ln it would creep up the boat ramp at idle .the boat was6,000 pounds . pulling down the road I had to be careful .it looked like a batlle ship behind the jeep!!!!!