Rear Axle Swap/Re-gear - JeepForum.com

 
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post #1 of 11 Old 06-19-2017, 03:48 PM Thread Starter
1996maroonzjf
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Rear Axle Swap/Re-gear

I have recently moved to Denver Colorado, and it immediately became apparent to me that a ZJ with the 4.0, 3.55 gears, and 31" tires was not practical for the area, and honestly, its a safety issue. I've nearly been rear ended a couple times, and even with OD locked out it really sucks having the pedal mashed to the floor and still loosing speed. I've started downshifting to 2nd gear to accelerate at all up hill.

So my plan is to find another rear axle that has 3.73 gears and swap that in, along with either re-gearing the HP Dana 30 that I swapped in a few years back, or trying to find a 3.73 HP30 to swap in. I don't do hardcore wheeling, I did mostly trail riding fire service roads and logging routes back home in the midwest, but this may change since I now live at the base of the Rocky Mountains. Also worth mentioning, I don't plan on going to a larger diameter tire.

A few questions -

-Would I be crazy to swap in another Dana 35C with 3.73 gears? I recently had the rear driveshaft re-built/balanced, and would like to avoid the extra expense of getting a different drive shaft for a 44A. I also like to jack the rear end up by the pumpkin, and I know you can't(shouldn't) do it with the 44A, but that's pretty minor.

- Lets say I do want to really upgrade to a ford 8.8. Realistically, without a welder, what is a ballpark price for the completed swap, assuming I can get a donor for around $100 at a pick and pull? Would it be at all necessary for a stock 4.0 and 31's?

-How rare are 3.73 HP30's? Everyone that I've seen at junkyards were 3.55 but Ill keep looking.

I don't plan on keeping this particular ZJ much longer (rust), but I do plan on finding a cheap rust free ZJ with a blown engine or transmission and swapping everything over (including axles) this winter. I don't mind swapping them into this one now and then into the new one over the winter.

Any input and or advice would be much appreciated!

Cheers


-Tim
96 4.0 Laredo, 42RE, NP242, HP30 & D35c 3.55, OME 2.5" HD Coils, Bilstein 5100s, IRO Adj. LCAs
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post #2 of 11 Old 06-19-2017, 04:32 PM
HighLonesome
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I don't think 3.73 is going to help that much. The 3.73 5.2 is doggy with 31s.
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post #3 of 11 Old 06-19-2017, 04:50 PM
PolkaPower
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The easiest, cheapest option would be to get a d44a and a hp 30 with 3:73 or just a lp 30 with 3:73.
That would bolt right in.

You can try to find a hp30 with 4:10s and then regear the rear to match but gear set up are costly and I've never come across any 4:10s in the junkyards yet.

Shops might charge 80$+ for labor so an 8.8 with brackets welded isn't exactly inexpensive but it is a good option for the long run.
There's nothing wrong with a d44a. It's plenty strong. Just needs a skid. For larger tires like 33s and up a truss is also a good idea.
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post #4 of 11 Old 06-19-2017, 04:59 PM
kg6mov
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3.73 HP30's are extremely rare. They were only available in some tow packages, and there's not a good way to identify them by the jeep trim/engine/option.

Going to 3.73 with 31's is still gonna be under geared compared to factory 3.55's and factory tires. 4.10 would get you just a little over factory, and it was a factory option in the XJ (manual, 2.5l).

There's a great calculator to let you compare gear ratios here: http://www.grimmjeeper.com/gears.html


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1984 F250, 460 BB, T19, work truck/future tow pig
1987 Mercedes 300D Turbo, the diesel daily, 30mpg in style

Quote:
Originally Posted by Texas ZJ1 View Post
I heard someone yell "mall crawler" from the back porch. I'll go see who said that. Be right back.
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post #5 of 11 Old 06-20-2017, 07:21 AM
LordHobbit
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If you choose a Ford 8.8, look for 4.10 gears. They should be fairly easy to find. You might be able to find an HPD30 with 4.10s also as stated by Kg6.

with the 8.8, you'll need a bracket kit and someone to weld it up. It isn't a difficult job and any semi-conscious welder should be able to do it in a few hours.

IRO has a bracket kit: http://www.ironrockoffroad.com/10559.html
ECGS also has one: http://eastcoastgearsupply.com/i-116...-brackets.html
Artec has a really nice one with a truss: http://www.artecindustries.com/ZJ_8.8_Swap_Kit
TNT also has a truss: https://www.tntcustoms.com/jeep_part...zj_tnt_customs

Do you have a small lift with the 31s?

Offroading is fairly popular in CO. You may change your mind about playing in the Jeep.

Edit: If I would bother to read your signature I would see that you have the OME coils. Way to go Hobbit ...

93 red ZJ 190k 4.0. Spent more money than I should have ...

Isn't red the only color a vehicle should be?
If at first you don't succeed, use more speed.

Last edited by LordHobbit; 06-20-2017 at 07:26 AM. Reason: not looking where I should
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post #6 of 11 Old 06-20-2017, 11:18 AM Thread Starter
1996maroonzjf
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Thanks for the thoughtful responses fellas. So the consensus, on here and around my office, seems to be 4.10 or nothing.

Well I guess I will have to put up with the nonexistent acceleration for the time being. The research will continue and the search begins for a 4.10 8.8 and a 4.10 HP30.

I've been doing quite a bit of googling and I seem to keep coming up with the same few posts. Is there a definitive 8.8 ZJ swap thread?

-Tim
96 4.0 Laredo, 42RE, NP242, HP30 & D35c 3.55, OME 2.5" HD Coils, Bilstein 5100s, IRO Adj. LCAs
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post #7 of 11 Old 06-20-2017, 12:43 PM
kg6mov
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There really isn't at this point, no.

I wouldn't do anything but the Artec truss for that, unless I was ordering an axle built from ECGS.


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1984 F250, 460 BB, T19, work truck/future tow pig
1987 Mercedes 300D Turbo, the diesel daily, 30mpg in style

Quote:
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I heard someone yell "mall crawler" from the back porch. I'll go see who said that. Be right back.
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post #8 of 11 Old 06-21-2017, 06:55 AM
Boone96ZJ
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When and if my D44a goes I will be ordering the 8.8 from ECGS. Already set up and ready to throw in there. But I can drive and pick mine up which isn't really an option for you but that is what I would do.

96 5.2 242 3" 32x11.5
http://www.jeepforum.com/forum/f13/1996-grand-cherokee-laredo-5-2-a-2570290/
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post #9 of 11 Old 06-21-2017, 10:31 AM
PolkaPower
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Currie axles would be near the same price wouldn't they? After all the add ons?
You can do front and rear 44s.
http://www.currieenterprises.com/roc...stom-frontends

This guy did that. I'm jelly.
http://forum.expeditionportal.com/th...FV-quot/page37
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post #10 of 11 Old 06-21-2017, 11:06 AM
kg6mov
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Yeah, ecgs would come in a little cheaper, but any of the axle builders are gonna be in about the same price range.

Not a bad way to go if you can float the cash and want it done. Building is fun, but you gotta have the time.


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1984 F250, 460 BB, T19, work truck/future tow pig
1987 Mercedes 300D Turbo, the diesel daily, 30mpg in style

Quote:
Originally Posted by Texas ZJ1 View Post
I heard someone yell "mall crawler" from the back porch. I'll go see who said that. Be right back.
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post #11 of 11 Old Yesterday, 01:54 PM
Spike6901
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Just an FYI...
I had 4.10's in a '99 XJ with 3" lift and 31's and it was just about right. It would run 80 on the highway and get 18mpg.
I currently have 3.55's in a '97 ZJ with 2.5" lift and it sucks...bad.

Future: '18 WK2 or a JL
Current: '97 ZJ - Lots of mods
Past: CJ-7, XJ, KJ, JKU
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