Jeep Cherokee axle in KB1


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Pile of Parts
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Post Tue Oct 29, 2019 8:38 pm

Jeep Cherokee axle in KB1

Anyone done this before? It was free, and the same wheel bolt pattern. Ratio is better, from an automatic Jeep.

Once you can go faster does the non synchro tranny become the problem? Down shifting is usually a challenge.

Thanks!

Earl
1949 KB1
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Golden Jubilee
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Post Wed Oct 30, 2019 1:01 pm

Re: Jeep Cherokee axle in KB1

I don't know how much the ratio change would affect your speed. The wheel bolt pattern will be the least of your worries swapping out the axles. Things to consider are, spring and axle height in comparison, is the chunk centered as the IH, driveshaft adaptation, brake lines, emergency brake, width of axle, spring perches. spring tension comparison, braking at higher speed etc. Seems like a lot of work for what you might get in speed gain. A complete driveline adaptation from engine to rear along with upgraded suspension and brakes is the only way to guarantee speed and comparable braking and suspension ability that work together.
With all that said, go for it, I'm curious to see how it works out.
Be safe, Bob

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Post Wed Oct 30, 2019 2:10 pm

Re: Jeep Cherokee axle in KB1

nikkinutshop wrote:
Captainbob, please!
A ratio change will not change the truck's speed. Only the engine to road speed relationship will change. A ratio of 3:73 over the OEM of 4:11 may allow the engine to push the truck to a higher speed at a given rpm. This may be possible only if the engine has the power to push the truck past the resistances that come into play when going faster.
This is where good brakes are important. Is the brake system able to convert the kinetic energy of motion into heat and not fade? I think a 20% speed increase may be compatible with OEM brakes. The load in the truck adds to the stopping kinetic energy. Reduce the load and there should be more brake left to handle a mild increase in speed.
My R120 could go over 90 miles per hour. I installed a 420 cubic inch V8 Diesel and 4X4 axles. The "R" had 4 wheel disc brakes. Stopping was never a problem.
I have posted the how to determine the engine revolutions per mile using the axle ratio and the tire diameter. This is simple mathematics.
Here is a copy and paste of what I wrote:
You need to calculate the circumference of tire by using 3.1415 X the diameter of 31.4 inches. Your tire circumference should be 98.643 inches or close to 8 feet. One mile is 5280. Divide 5280 by 8 feet ( 98.643"). You should get 3063 revolutions in a mile. One mile in a minute is 3063rpm.
40 mph is 2/3 of 60 mph. Divide 3063 by 3 and multiply that new number by 2 and you get an rpm

Spring mounts are an easy move. Adapting the hydraulic system to the replacement axle is as easy as replacing the parts that should be replaced anyway.
BTW. The center section, or chunk, as you have named it, can be off-center a few inches and not affect the driveline.
Last edited by nikkinutshop on Wed Oct 30, 2019 11:10 pm, edited 3 times in total.
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Golden Jubilee
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Post Wed Oct 30, 2019 2:27 pm

Re: Jeep Cherokee axle in KB1

Earl wrote:Anyone done this before? It was free, and the same wheel bolt pattern. Ratio is better, from an automatic Jeep.

Once you can go faster does the non synchro tranny become the problem? Down shifting is usually a challenge.

Thanks!

Earl
1949 KB1

The only problem here is the guy stirring the gears. Yes, you may have to down-shift sooner. Learning a non synchro transmission is achievable. CB89 does this hundreds of time every day. But then CB89 is a brighter bear.
You do not mention the new to you gear ratio in the free differential. Why is it free and why is it not in the original vehicle. Maybe you are getting a worn out POS.
I was given a Ford Explorer 8.8 complete disc brake axle for my 1940 Ford. (read this as free) I bought everything needed to rebuild the axle to like new. The parts were about $1400. I think this is a good price for what is now a new axle.
If I had the space, I would be fitting different transmissions to a few Old IHC engines. I know this can be done, but I will not be the one making it happen. Surely a later model IHC transmission with synchro can be fitted.
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive

Golden Jubilee
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Post Wed Oct 30, 2019 3:14 pm

Re: Jeep Cherokee axle in KB1

Examples: No arguments, don't care, this is my experience.
Gear---Tire"---speed---rpm
4.77----32-----65-----3256
4.11---32-----65------2805
3.55---32-----65------2423
3.55---32-----75------2796
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Golden Jubilee
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Post Wed Oct 30, 2019 4:41 pm

Re: Jeep Cherokee axle in KB1

nikkinutshop wrote:Captainbob, please!
Almost everything you wrote is incorrect.
A ratio change will not change the truck's speed. Only the engine to road speed relationship will change. A ratio of 3:73 over the OEM of 4:11 may allow the engine to push the truck to a higher speed at a given rpm. This may be possible only if the engine has the power to push the truck past the resistances that come into play when going faster.
This is where good brakes are important. Is the brake system able to convert the kinetic energy of motion into heat and not fade? I think a 20% speed increase may be compatible with OEM brakes. The load in the truck adds to the stopping kinetic energy. Reduce the load and there should be more brake left to handle a mild increase in speed.
My R120 could go over 90 miles per hour. I installed a 420 cubic inch V8 Diesel and 4X4 axles. The "R" had 4 wheel disc brakes. Stopping was never a problem.
I have posted the how to determine the engine revolutions per mile using the axle ratio and the tire diameter. This is simple mathematics.
Here is a copy and paste of what I wrote:
You need to calculate the circumference of tire by using 3.1415 X the diameter of 31.4 inches. Your tire circumference should be 98.643 inches or close to 8 feet. One mile is 5280. Divide 5280 by 8 feet ( 98.643"). You should get 3063 revolutions in a mile. One mile in a minute is 3063rpm.
40 mph is 2/3 of 60 mph. Divide 3063 by 3 and multiply that new number by 2 and you get an rpm

Spring mounts are an easy move. Adapting the hydraulic system to the replacement axle is as easy as replacing the parts that should be replaced anyway.
BTW. The center section, or chunk, as you have named it, can be off-center a few inches and not affect the driveline.

I'll never understand why someone has to always find fault with a post or response instead of just offering their experience or knowledge in a friendly post. I don't intend to start any riff here so I'll defer to your post even though your statement that almost everything I wrote is incorrect, is not correct.

Golden Jubilee
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Post Wed Oct 30, 2019 4:51 pm

Re: Jeep Cherokee axle in KB1

I think you know why misinformation has to be challenged.
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive

Golden Jubilee
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Post Wed Oct 30, 2019 9:27 pm

Re: Jeep Cherokee axle in KB1

My take is this: You bought an antique truck, if you wanted a modern truck, that is easy to drive, then buy that. Non syncro trans is part of the deal. It isn't hard to learn, but you have to pay attention and it will never be a fast shifting vehicle.
A K series pick-up can take a modest axle ratio change, but it will be a trade off between slower engine RPM and load carrying ability. Most don't use pick-ups as trucks any more, but rather as cars with only one seat.
The GRD was never a powerhouse, and how well it will take a ratio change I will leave to those who have done it.
When I drive my K-7's I drive slower, and more relaxed. Shifts are slow to allow for the engine speed to drop and match the road speed. With the wide ratio jumps ( when compared to a modern semi's trans) I find it easier to ease off the throttle and slip the trans into neutral then release the throttle while stepping on the clutch and selecting the next higher gear. Down shifting is a little more difficult, those I normally double clutch, as the reason for down shifting is likely that the grade is too much for the gear your in, and the idea is to make the shift as quick as possible to loose the least road speed . With the K-7's two speed axle in the mix, you learn to take your time and not rush shifting.
All in the joy of driving something that has been around for over 70 years,

Yard Art
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Post Thu Oct 31, 2019 7:21 am

Re: Jeep Cherokee axle in KB1

http://www.csgnetwork.com/rearendgearcalc.html
hello. here is where you can check speed diff. ratio and on my kb-3 i change housing to fit a colorado 2005 with a ratio of 3.73, very good, i try to find gear to fit on oem housing with a 3.73 gear set or if i find a 3.55.

Rusty Driver
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Post Fri Nov 01, 2019 10:25 am

Re: Jeep Cherokee axle in KB1

That's a useful calculator. Thanks.
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