4.30 geared rear with 4.27 geared front questions

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Phils67
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4.30 geared rear with 4.27 geared front questions

Postby Phils67 » Thu May 10, 2018 3:37 pm

As you all know differential projects arent cheap. Here is my dilemma... i have a 44 front under my truck, closed knuckle with a 4.27 gear set. I started building an open knuckle 44 front and planned on going 8 lug with disc brakes. I built the diffs a few yesrs ago and the internals are all new. I have a 60 rear i plan to build as well. Since i am on a budget and already have a good gear set and shafts in my front, with budget in mind, would it be easier to just add 8 lug hubs and disc to my front and build the 60 rear with a 4.30 gear set? Word on the trails is that this ratio works with 4.27 front gears when in 4x4 with zero issues. Has anyone done this? What have you found from doing this? Can i swap the J20 spindles, brakes and hubs over to my closed knuckle 44 front? I need advice before i spend a sh!t ton of cash i don't really have! Im at the point i can either move forward with my open knuckle build or deadhead the whole project and just focus on the rear which requires a ton less work and money and since i have all the knuckle-out parts the front would be an easy conversion if it works. Advice from prior experience is extremely appreciated!
Big Ugly 1967 J2000 4.0MPI/T18/D20/locked 44/welded 53/35s
Past Jeeps:
77 Cherokee S
89 MJ
91 YJ
98,98,98,99,01 XJs
00 TJ
03 KJ liberty
06 Commander
Half of a M715
None in that order and I'm sure im forgetting something

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Phils67
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Re: 4.30 geared rear with 4.27 geared front questions

Postby Phils67 » Thu May 10, 2018 4:05 pm

My biggest concern is the spindle and hub swap for the front. Gear ratio isnt even my concern as i could just go 4.56 front and rear and be done with it. I want a disc brake front. I want to run my detroit locker setups. I want to have 8 lug front to match the rear. I DON'T want to deal with spring mount positions and all that other stuff i don't have issues with. I have a closed knuckle, i have accepted you couldn't pull a u-turn in yankee stadium without at least using reverse once. That part i accept. What i really need to know more than anything is if the J20 spindles-out will work on the closed 44 without major mod. I want to build the rrar and be back driving in a weekend. This truck is my mule. It can not afford down time. So what is the front spindle,hub,brake concerns?
Big Ugly 1967 J2000 4.0MPI/T18/D20/locked 44/welded 53/35s
Past Jeeps:
77 Cherokee S
89 MJ
91 YJ
98,98,98,99,01 XJs
00 TJ
03 KJ liberty
06 Commander
Half of a M715
None in that order and I'm sure im forgetting something

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Stuka
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Re: 4.30 geared rear with 4.27 geared front questions

Postby Stuka » Thu May 10, 2018 8:16 pm

This is entirely normal and will not be an issue. Its common to have gearsets that are a few points off when you have different front and rear axles. Such as the 4.09/4.10/4.11 gearsets.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Stock, but not for long!
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

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Kaiserman
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Re: 4.30 geared rear with 4.27 geared front questions

Postby Kaiserman » Thu May 10, 2018 9:03 pm

This is what I was talking about with you earlier. You can use the later internally splined hubs in place of the earlier hubs I used with no problem.

http://www.ifsja.org/forums/vb/showthread.php?t=70297
1971 J2500 Gladiator Custom-Cab Platform Stake on 126" wb. B350/T18A/D20 D60/D60-3 w/locker 4.10's Ramsey 8klb PTO winch, Day-brook dump. 235/85R16's
1969 J3800 Gladiator 3407Z Camper Truck. B350/T18A/D20 D44/D60-3 w/4.10's
1968 J3800 Gladiator 3406Z Custom Cab 160" wheel base dually. 24K miles. B350/T18A/D20 D44HD/D70 posi w/4.88's 7/50-16's
1963 J300 Gladiator Townside Buick 350/Th400/D20 D44/D53 4.27 gears. Stock Meyers plow, 225/95R16's

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Phils67
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Re: 4.30 geared rear with 4.27 geared front questions

Postby Phils67 » Fri May 11, 2018 2:16 am

Stuka wrote:This is entirely normal and will not be an issue. Its common to have gearsets that are a few points off when you have different front and rear axles. Such as the 4.09/4.10/4.11 gearsets.


Im concerned with in this situation, what part would fail first. That slight difference in a truck on 35s with front and rear lockers sounds like an eventual transfer case grenading during a snow storm
Big Ugly 1967 J2000 4.0MPI/T18/D20/locked 44/welded 53/35s
Past Jeeps:
77 Cherokee S
89 MJ
91 YJ
98,98,98,99,01 XJs
00 TJ
03 KJ liberty
06 Commander
Half of a M715
None in that order and I'm sure im forgetting something

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Stuka
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Re: 4.30 geared rear with 4.27 geared front questions

Postby Stuka » Fri May 11, 2018 6:25 am

Phils67 wrote:
Stuka wrote:This is entirely normal and will not be an issue. Its common to have gearsets that are a few points off when you have different front and rear axles. Such as the 4.09/4.10/4.11 gearsets.


Im concerned with in this situation, what part would fail first. That slight difference in a truck on 35s with front and rear lockers sounds like an eventual transfer case grenading during a snow storm


You get more binding when you turn than the tiny difference in gearing. Vehicles have come from the factory with gearing differences like this since the dawn of the 4wd. And technically the larger your tires is, the smaller that difference becomes.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Stock, but not for long!
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

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derf
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Re: 4.30 geared rear with 4.27 geared front questions

Postby derf » Wed May 16, 2018 7:14 am

Phils67 wrote:
Stuka wrote:This is entirely normal and will not be an issue. Its common to have gearsets that are a few points off when you have different front and rear axles. Such as the 4.09/4.10/4.11 gearsets.


Im concerned with in this situation, what part would fail first. That slight difference in a truck on 35s with front and rear lockers sounds like an eventual transfer case grenading during a snow storm


The difference in diameter from a new tire and one that's near bald is a bigger difference than 4.27 to 4.30.

Heck, the difference between over inflated and under inflated tires can be more than that still.

You're not going to blow up a transfer case or chuck u-joints because you're running gear sets that are within 1% of each other. Especially in a low traction situation like snow. Any binding that would cause an issue in the snow will be worked out by one of your 4 tires slipping just a hair once in a while. But in the snow, you aren't even going to notice it.

It's not going to be an issue at all. Don't worry about it.

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tgreese
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Re: 4.30 geared rear with 4.27 geared front questions

Postby tgreese » Wed May 16, 2018 7:34 am

Heck, the difference between over inflated and under inflated tires can be more than that still.
...


I hate to bring up this argument again, but within normal range, tire circumference does not change measurably with inflation. Try it. Put a mark on your fully inflated tire, a mark on the ground, and roll forward 10 turns. Mark that spot, and roll back. Repeat with less tire pressure. You will measure the same distance.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 FCA Jeep Cherokee KL Trailhawk, ECO Green

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Re: 4.30 geared rear with 4.27 geared front questions

Postby SJTD » Wed May 16, 2018 7:57 am

I've been going round and round on that idea.

It made sense until I bought a '16 Jetta. It uses compares tire rotation to sense underinflation.
Sic friatur crustulum

'84 GW with Nissan SD33T, early Chev NV4500, 300, narrowed Ford reverse 44, narrowed Ford 60, SOA/reversed shackle in fornt, lowered mount/flipped shackle in rear.

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Stuka
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Re: 4.30 geared rear with 4.27 geared front questions

Postby Stuka » Wed May 16, 2018 7:58 am

SJTD wrote:I've been going round and round on that idea.

It made sense until I bought a '16 Jetta. It uses compares tire rotation to sense underinflation.


No, it has tire pressure sensors in each tire. When you remove the tire, you will see a device on the inside of the valve stem, this measures tire pressure.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Stock, but not for long!
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

SJTD
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Re: 4.30 geared rear with 4.27 geared front questions

Postby SJTD » Wed May 16, 2018 2:12 pm

That's not what the owner's manual says.
Sic friatur crustulum

'84 GW with Nissan SD33T, early Chev NV4500, 300, narrowed Ford reverse 44, narrowed Ford 60, SOA/reversed shackle in fornt, lowered mount/flipped shackle in rear.

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Stuka
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Re: 4.30 geared rear with 4.27 geared front questions

Postby Stuka » Wed May 16, 2018 2:39 pm

SJTD wrote:That's not what the owner's manual says.


Had to look this one up. Turns out you are right, they changed it. Unlike every other car maker that uses a direct sensor to tell the car exactly what the air pressure in the tire is, VW has switched to this other method in 2015. So the car has no clue what the air pressure is in any of the tires, only that one of them may be turning faster than the others. Unfortunately the system won't know about a flat tire for quite some time later. If you get a flat that loses air quickly, it won't alert you. The TPMS versions know immediately.

But, the point is, a tire with less air will turn more slowly. Which is a given, as the "rolling diameter" is from the ground to the center of the wheel.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Stock, but not for long!
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

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Phils67
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Re: 4.30 geared rear with 4.27 geared front questions

Postby Phils67 » Wed May 16, 2018 4:14 pm

Idk. Still seems weird. Maybe I'll give it a try. Worst case if i dont care for it i could always regear again. Currently im in the gathering info and parts stage with this. First has to be frame repair, then reconfigure this suspension, then i can get back to the axle build
Big Ugly 1967 J2000 4.0MPI/T18/D20/locked 44/welded 53/35s
Past Jeeps:
77 Cherokee S
89 MJ
91 YJ
98,98,98,99,01 XJs
00 TJ
03 KJ liberty
06 Commander
Half of a M715
None in that order and I'm sure im forgetting something

MJMadness
Posts: 92
Joined: Wed Aug 06, 2014 1:46 pm

Re: 4.30 geared rear with 4.27 geared front questions

Postby MJMadness » Thu May 17, 2018 8:06 pm

Stuka wrote:This is entirely normal and will not be an issue. Its common to have gearsets that are a few points off when you have different front and rear axles. Such as the 4.09/4.10/4.11 gearsets.


This.

And a more drastic example is coupling a Ford 9" with a DanaXX front, the 9" typically comes with 3.50 gears and the Dana will have 3.55. It works fine, as again it's close enough that it's just another variable that normal tire slippage can account for.


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