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Mj Front Axle/lift Question


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#1 MJeep

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Posted 17 October 2012 - 11:48 AM

Ive got an 89 MJ 2wd 2.5L 4spd. My teacher gave me the green light to put an xj front axle in and a front lift next week. Now the questions start:
1. What ratio am i looking for in the front axle?(is there one to match my current rear D35)
2. I'm going to have 31s all around and do alot of street driving but also do moderate trail riding, what lift would do the job without welding, and what all do i need? i was thinking 3-4".
3. Are there any other parts I'm going to need and what problems should i expect to run into? (Brake lines, etc)

Thanks alot

1989 SporTruck
2.5L 4spd 2wd
93,500mi
Small truck, Big plans


#2 Geonovast

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Posted 17 October 2012 - 11:53 AM

Your front axle HAS to match the rear in ratio.

You don't need any lift to run 31s.

-Correy

99 XJ, 4.0 HO/AW-4/NP 231, D30/8.25 - Parked The MJs formally known as mine.

88 MJ, 2.5 TBI/AX-4, D35 - DD                             CC on Facebook!
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Do I have an AX-15 or BA 10/5? What's my factory axle ratio? Common Jargon definitions.


#3 MJeep

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Posted 17 October 2012 - 11:59 AM

It doesnt have a transfer case yet, so the ratios won't interfere with each other as of yet. Since I'm putting in the axle, i want to put the lift in, being that the front end will be all torn apart anyway, and ill have the proper tools

1989 SporTruck
2.5L 4spd 2wd
93,500mi
Small truck, Big plans


#4 Garvin

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Posted 17 October 2012 - 12:15 PM

For a proper front lift you'll need: longer shocks to accommodate the lift, the springs of your choice for the lift, longer sway bar links, longer brake lines, and a longer (or adjustable) track bar. You can put a drop pitman arm on also to correct the steering angles some from the lift but don't need to. If you do put a drop pitman arm on, make sure you put a drop track bar bracket on that will match the amount of drop the pitman arm gives or you will get bump steer.

I believe the rear of your truck has 3.73's but make sure on that as the 4.10 ratio was an option for the trucks. If you pop off the rear differential cover, the ring gear should be stamped with two numbers. Divide the larger number by the smaller number to get your ratio (example: 41 10 41/10=4.10). If you can find a donor vehicle with the same setup then you can steal everything from the front end, including the drive shaft. The rear drive shaft will need to come out of a Comanche with the same options or get custom made as Cherokee ones won't fit. If the 4spd is manual (AX4) then now might also be a good time to swap in an AX5 to get overdrive as you will need to swap the transmission to a 4wd one to put the transfer case in. You can also swap in an AX15 with a Dakota 4cyl bellhousing.
1986 Jeep Comanche...Project Mutt
Long Bed, 5.7L V8 TPI, AX15, NP231, 60HP/10.25, Custom 3-link long arm, ~6" lift, 15/38.5 Ground Hawgs, roll bar, recessed winch, and a whole lot less sheet metal.

1992 Jeep Comanche
Short Bed, 4.0L I6 HO, AX15, NP231, 30HP/D35

...RIP...
1990 Jeep Cherokee XJ 207774 miles
4.0L I6, AW4, NP231, AA SYE, TW Driveshaft, 8" Rusty's LA lift, 30HP/44, 4.56 gears, OX locker rear, Olympic Top Hat roof rack, 36" IROK's

#5 MJeep

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Posted 17 October 2012 - 12:21 PM

Thanks Garvin, I'm leaning towards this Rubicon Express RE6020 http://www.rubiconex...&t_pn=R/ERE6020
The transmission will need replaced, but thats a next year job.

1989 SporTruck
2.5L 4spd 2wd
93,500mi
Small truck, Big plans


#6 MJeep

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Posted 17 October 2012 - 12:35 PM

Any specific year XJ or MJ i should look for as a donor?

1989 SporTruck
2.5L 4spd 2wd
93,500mi
Small truck, Big plans


#7 Geonovast

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Posted 17 October 2012 - 01:18 PM

I would look for an 94ish+ XJ with the 2.5, 5 speed, and 8.25 rear end. This will give you your AX-5 with an external slave, a 231, non- D35 rear end non-disco HP D30, and the 4.10 axle gearing that you're going to want.

This is an ideal situation of course, If you're looking to match the front to the rear and don't want to change the rear (the 5th gear in an AX-5 will be useless on 3.55s with 31s), you can get 3.55 gears from a 2.5/4 speed or 4.0/automatic.

-Correy

99 XJ, 4.0 HO/AW-4/NP 231, D30/8.25 - Parked The MJs formally known as mine.

88 MJ, 2.5 TBI/AX-4, D35 - DD                             CC on Facebook!
Think of the children; Lock your CAD today!  Having trouble posting pictures?
Do I have an AX-15 or BA 10/5? What's my factory axle ratio? Common Jargon definitions.


#8 Eagle

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Posted 17 October 2012 - 01:21 PM

Ive got an 89 MJ 2wd 2.5L 4spd. My teacher gave me the green light to put an xj front axle in and a front lift next week. Now the questions start:
1. What ratio am i looking for in the front axle?(is there one to match my current rear D35)
2. I'm going to have 31s all around and do alot of street driving but also do moderate trail riding, what lift would do the job without welding, and what all do i need? i was thinking 3-4".
3. Are there any other parts I'm going to need and what problems should i expect to run into? (Brake lines, etc)

Thanks alot


With a 2.5-liter 4-speed, your rear axle is almost certainly a 3.54. Fortunately for you, that's the most common axle ratio in 4.0-liter XJs, because that's what the factory used with the automatics. Just bolt it in.

To echo a previous post, you do not need a lift to run 31" tires, and you do not need a lit for moderate trail riding. Keep it at stock height, drive it for a year, THEN decide if you really need a lift. Once you lift, you've just dug a deep hole that you keep pouring $$$$ into.
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#9 mvusse

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Posted 17 October 2012 - 04:52 PM

I'm going against the grain here. You don't need a lift for 31s, but it would look better and work better off road with a bit of lift. I would go with a budget boost: 1.75" pucks up front, depending on how the truck sits and your preference either leave the rear alone or get a pair of 2" Chevy drop shackles for ~3/4" lift in the rear. Your current brake hoses will still be long enough and it is a small enough lift that you don't need to worry about control arms or track bar. You will want to get the longer sway bar links from a newer XJ, though.

To match your current rear axle ratio you would need a 3.54 or 3.55 ratio front axle, these are plentiful with a 4.0/automatic transmission combo. If you can get one from between 95 and 99 it will be high pinion, non-disconnect and have the larger (stronger) u joints.

With 31" tires behind a 4 cylinder I would instead opt for 4.10 ratio axles. These would come behind a 4 cylinder/5 speed stick. Not as common as the 3.55 axles, but not all too difficult to find. I would get both axles, front driveshaft, transmission and transfer case all from the same vehicle (95-99 XJ WITHOUT ABS would be optimal), and get a speedometer cable from a 84-90 4wd XJ with a 4 cylinder because your current one would be too short, and swap the speedo pickup out of your transmission and into the new transfer case. It won't be completely accurate but you can always get a new gear at a later time.
87 Comanche Pioneer 4.0 4x4 auto, Wilbur. 6.5" lift, Aussie lockers, Jawz JP Customs winch bumper, XRC10 winch and 35x12.50 Maxxis Mudders. Lots of cutting, lots of rust(holes), lots of dents.
87 Comanche 2.5 4x4 5 speed, The Purple People Eater, stock daily driver.
96 Cherokee Sport 4.0HO, Sparkles. mild lift, 32s, 2wd converted to Selec-Trac. Built for my daughter.

#10 MJeep

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Posted 18 October 2012 - 12:06 PM

Ive read XJ shocks won't work. Which shocks should i run?
And ive been contemplating a lift for a long time. ive got 31s on the rear and they rub on the trails i run, and i can't clear half of the things i could in my old truck. I figure 3" will give a good stance, good versatility, and not consist of welding on any parts. Anything over 3" would ruin the truck.

1989 SporTruck
2.5L 4spd 2wd
93,500mi
Small truck, Big plans


#11 randomguy310

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Posted 18 October 2012 - 08:02 PM

I'm sure all 2.5 came with 4.10:1 ratios... look it up and auto 2.5s came with 4.56:1 ratio

#12 Geonovast

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Posted 18 October 2012 - 08:22 PM

No, not all 2.5s came with 4.10s

2.5 with 4 speed = 3.55
2.5 with 5 speed = 4.10
2.5 with auto = early had 4.56, later could be 4.10 or 4.56

-Correy

99 XJ, 4.0 HO/AW-4/NP 231, D30/8.25 - Parked The MJs formally known as mine.

88 MJ, 2.5 TBI/AX-4, D35 - DD                             CC on Facebook!
Think of the children; Lock your CAD today!  Having trouble posting pictures?
Do I have an AX-15 or BA 10/5? What's my factory axle ratio? Common Jargon definitions.


#13 mvusse

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Posted 18 October 2012 - 09:02 PM

Later year XJs (97+?) they used 4.10 gears with the 2.5 no matter what transmission is had.
87 Comanche Pioneer 4.0 4x4 auto, Wilbur. 6.5" lift, Aussie lockers, Jawz JP Customs winch bumper, XRC10 winch and 35x12.50 Maxxis Mudders. Lots of cutting, lots of rust(holes), lots of dents.
87 Comanche 2.5 4x4 5 speed, The Purple People Eater, stock daily driver.
96 Cherokee Sport 4.0HO, Sparkles. mild lift, 32s, 2wd converted to Selec-Trac. Built for my daughter.

#14 mnkyboy

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Posted 18 October 2012 - 09:16 PM

Seems that a lot of 1986 2.5ls came with 3.73 gears.


1989 MJ 2.5L bobbed SWB AX4 231 Non disco D30/D44 Disc brakes,4.88s,lockers, 6.5"-7"lift,SOA rear, 33x12.5x15, hidden 10k winch.

Working on Phase 2- 2.5l MPI,0.060 over, Mopar Purple cam, inertia ring,4.0l TB, Bosch yellow tops, adjustable MAP, ported intake, ported poweraid TB spacer, header, and Flow Kooler. Ford 3/4 ton HP D44/Sterling 10.25, 5.38s, locked, and disc brakes. AX15, 231 6 pinion planetaries, wide chain, doubler 7.4:1 double low. Custom 3 link front, SOA rear,37x12.50-17s, exo.

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#15 ParadiseMJ

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Posted 18 October 2012 - 09:18 PM

So, not to hijack, (I'll go away if I'm stepping on toes) but does that mean I could install my waiting 8.8 with 4.10's and still run the 3.07 D30 if the front driveshaft is removed?? Until I get an HP D30 with matching gears??

Is the front just freewheeling then?

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#16 mnkyboy

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Posted 18 October 2012 - 10:15 PM

You don't even have to go that far,just don't shift into 4wd till you match the gears.
1989 MJ 2.5L bobbed SWB AX4 231 Non disco D30/D44 Disc brakes,4.88s,lockers, 6.5"-7"lift,SOA rear, 33x12.5x15, hidden 10k winch.

Working on Phase 2- 2.5l MPI,0.060 over, Mopar Purple cam, inertia ring,4.0l TB, Bosch yellow tops, adjustable MAP, ported intake, ported poweraid TB spacer, header, and Flow Kooler. Ford 3/4 ton HP D44/Sterling 10.25, 5.38s, locked, and disc brakes. AX15, 231 6 pinion planetaries, wide chain, doubler 7.4:1 double low. Custom 3 link front, SOA rear,37x12.50-17s, exo.

http://www.comanchec...php?f=7&t=17196

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#17 Eagle

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Posted 18 October 2012 - 10:16 PM

So, not to hijack, (I'll go away if I'm stepping on toes) but does that mean I could install my waiting 8.8 with 4.10's and still run the 3.07 D30 if the front driveshaft is removed?? Until I get an HP D30 with matching gears??

Is the front just freewheeling then?


You could run mis-matched gears and leave the front driveshaft in place ... as long as you never put the lever in 4WD. Yes, if you remove the driveshaft there is nothing to connect the front and rear axles, so mis-matched gears won't matter.
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