62mm Throttle Body or 8.25 Rear Differential Swap.

[kastein]

Need perches and tubes welded, shock mounts, new ubolts and ebrake cables, and some other stuff.

Oh you will need a different driveshaft going 35 to 8.25 - a bit shorter. For a 95 or earlier get a 95 or earlier 8.25 with the same drivetrain (engine, auto or manual, and 4x4 or 4x2) for a 96 and later get a 96 and later 8.25 shaft.

 

[streetxj]

Need perches and tubes welded, shock mounts, new ubolts and ebrake cables, and some other stuff.

Oh you will need a different driveshaft going 35 to 8.25 - a bit shorter. For a 95 or earlier get a 95 or earlier 8.25 with the same drivetrain (engine, auto or manual, and 4x4 or 4x2) for a 96 and later get a 96 and later 8.25 shaft.

So the 96 and later 4x4 driveshaft is the same length as the 4x2 driveshaft?

Thanks for the info.

 

[kastein]

Nope, you misunderstood, sorry.

Things that affect rear ds length:
4cyl vs 6cyl - I think 4cyl are longer but not sure
auto vs manual - manual are longer
4x4 vs 4x2 - 2wd are much longer, like 6 to 8 inches or more
rearend (35 or 44/8.25) - 44/8.25 are around an inch shorter
95- vs 96+ - one is a few inches longer than the other, think its the old ones

Np231 vs np242 doesn't change anything.

So basically the shortest shaft you can get is probably a 6cyl auto 4x4 8.25 made after 96. The longest will be a 4cyl manual 4x2 d35.

Oh, MJ shafts are way longer too, longbeds especially.

Iirc all 4x4 rear shafts have 27 spline yokes. I know 4x2 manual renix era MJs with 4cyls got 21 spline yokes, not sure about any others, I believe it is because the transmissions have the same spline count regardless of 4x4 vs 4x2 status in those years, need to find out if it depends on auto vs manual, 4 vs 6cyl, and what exact year split. I discovered that when I shortened a 4cyl 4speed manual 4x2 MJ shaft for my 4x4 6cyl manual MJ and the damn yoke was a mile from fitting on. So I had to knock the ujoint out and put a different yoke on it.

 

[streetxj]

Nope, you misunderstood, sorry.

Things that affect rear ds length:
4cyl vs 6cyl - I think 4cyl are longer but not sure
auto vs manual - manual are longer
4x4 vs 4x2 - 2wd are much longer, like 6 to 8 inches or more
rearend (35 or 44/8.25) - 44/8.25 are around an inch shorter
95- vs 96+ - one is a few inches longer than the other, think its the old ones

Np231 vs np242 doesn't change anything.

So basically the shortest shaft you can get is probably a 6cyl auto 4x4 8.25 made after 96. The longest will be a 4cyl manual 4x2 d35.

Oh, MJ shafts are way longer too, longbeds especially.

Iirc all 4x4 rear shafts have 27 spline yokes. I know 4x2 manual renix era MJs with 4cyls got 21 spline yokes, not sure about any others, I believe it is because the transmissions have the same spline count regardless of 4x4 vs 4x2 status in those years, need to find out if it depends on auto vs manual, 4 vs 6cyl, and what exact year split. I discovered that when I shortened a 4cyl 4speed manual 4x2 MJ shaft for my 4x4 6cyl manual MJ and the damn yoke was a mile from fitting on. So I had to knock the ujoint out and put a different yoke on it.

Oh okay. Thanks for clearing it out. I wonder how common the 97-01 4x2 4.0 auto cherokees with 8.25 rear ends are, so I can grab a drive shaft from one of them. My jeep build date was 4/96. Looks like I'm going to be looking around in junkyards during my summer vacation. Due to time and money I'm going with the throttle body first (now), then the differential later on this year. Besides the differential, now I know that I also have to get the driveshaft and new rear shocks since mine look old and rough, even though they are firm and still function good. But since I have to take them out, might as well get new ones. I don't do burnouts, donuts, or floor it from a dead stop or climb hills with it. It has pretty small/light wheels, it is open differential and I drive on flat streets (south florida). The truck was never abused and has always been well taken care off, so I don't think that my rear differential is a ticking time bomb. I'll just feather the throttle when I make right turns on wet roads for now.

 

[kastein]

Since you need a slightly shorter shaft, worst case you can have yours cut down at a drivetrain shop. I had one done a while ago and iirc it ran me 125 bucks for a shorten/balance. Been doing my own since then with somewhat mixed results, but all fine for a beater.

Upper shock bolts were a bear on my 96, the bolts broke and the weldnuts were very solidly MIGed in place so I had to go through the floor to get at them. No fun. I would just unbolt the low end and swap rears if your shocks are fine.

Edit: you will need either the ubolts that were used on the 8.25 donor or preferably new ones. The 8.25 has larger axle tubes and the 35 bolts will not fit over it.

 

[Talyn]

A 8.25 would be nice, but don't count on the trash-lock still being good.

On a stock engine I would stick with a 60mm throttle body. It improved throttle response noticeably on mine . If you are planning on going with a stroker in the future I would get the 62 mm. www.strokedjeep.com

 

[nick86]

baby steps brother, I did the 60 mm throttle body, than upgraded to 8.25 with and ausie locker.

 

[streetxj]

Thanks for your help guys.

I agree with you Nick. Baby steps.

 

[nick86]

Thanks for your help guys.

I agree with you Nick. Baby steps.

well I actually locked the front in between, but since didn't ask about the front, I left that out.

 

[IXNAYXJ]

Need perches and tubes welded, shock mounts, new ubolts and ebrake cables, and some other stuff.

Oh you will need a different driveshaft going 35 to 8.25 - a bit shorter. For a 95 or earlier get a 95 or earlier 8.25 with the same drivetrain (engine, auto or manual, and 4x4 or 4x2) for a 96 and later get a 96 and later 8.25 shaft.

We retained our stock 2WD driveshaft when we swapped the stock D35 for the 8.8. You do need a flange adapter, though.

-Matt

 

[streetxj]

well I actually locked the front in between, but since didn't ask about the front, I left that out.

Yeah, I don't have a front differential so don't worry about it.

 

[streetxj]

We retained our stock 2WD driveshaft when we swapped the stock D35 for the 8.8. You do need a flange adapter, though.

-Matt

Cool. Yeah, there's even more modifications to be made for the 8.8 than the 8.25 differential swap so I'm not going with that route, unless I hit the lotto. Then I'll redo who the suspension so it can sit lower like Gradon's 96 and put in a turbo 4.6 stroker and improve the AW4 trans even more. All I can do for now is dream about it. lol
Thanks for the advice Matt. I guess D35's are more common in 2wd jeeps.

 

[nick86]

Here is what I did, got A 29 spline 8.25, let it sit till I could afford a locker for it. Did my engine upgrades in between. Than me & the g/f installed the rear in one afternoon. remember new u-bolts, possible brake lines,brakes, wheel cylinders, e-brake cables.

 

[kastein]

We retained our stock 2WD driveshaft when we swapped the stock D35 for the 8.8. You do need a flange adapter, though.

-Matt

yeah, I was talking about the 8.25 - I don't know offhand the pinion length and hypoid offset of the 8.8, so I don't generally tell people anything about driveshaft length when swapping to one out of fear of misleading someone.

 

[streetxj]

I took a closer look at my rear differential and it's the chrysler 8.25. :gee: The bottom part of the "pumpkin" is flat and not roundish like the dana 35 and the cover as a larger bubble and small flat area which is typical of the 8.25. Overall the whole rear axle looks thicker than the dana 35. I got confused cause one of the two metal tags read "35". They are kinda oxidized. Maybe it just means that I have 3.55's. Still a an open differential though. At least it's the stronger rear axle. Since mine is a later 96' it might have one of the first 29 spline versions. Who knows. Here's my vin if anybody can identify what I have: 1J4FT67S1TL239940

 

[kastein]

Probably a 27 spline in 96 but you never know.

If you get an LSD for it, get a 29 spline one and put it in, then install 29 spline shafts and now you have a 29 spline 8.25.

Installing an LSD will require minor gear work, but it's a side adjuster axle, so no bearing pullers or shims or micrometers or presses are required. Might have to pay someone a 12 pack to get the new bearings pressed onto it (unless it comes with the old bearings in good shape and the races are still matched to the appropriate sides) and you'll need a dial indicator to set backlash back to what it was plus a torque wrench and a new set of ring gear bolts, but I think that's about it.

Basically, steps are:
take a gear pattern using marking paste, photograph it
measure backlash using dial indicator
remove axleshafts and carrier from diff, making sure to keep carrier bearing caps with the side they came from and properly oriented (they may already be stamped with markings to help with this)
remove ring gear from carrier (I forget whether they are left hand thread bolts, make sure before trying to unscrew them)
discard old ring gear bolts
replace bearings on new LSD carrier if necessary
install ring gear on carrier using new ring gear bolts
install carrier into differential
use side adjusters to adjust carrier location until backlash/pattern are the same as they were before, set carrier bearing preload, recheck backlash/pattern, torque carrier bearing cap bolts to spec, recheck backlash/pattern, repeat as necessary
install 29 spline shafts, cover, gear lube

and now you have a 29 spline LSD 8.25. Literally everything in the 8.25 except the carrier, spider gears, and shafts is exactly the same between 27 and 29 spline, so switching to an LSD carrier is the ideal time to upgrade the shafts as well.

I think the only truly custom/special tool (aside from the usual torque wrench/dial indicator etc) is the side adjuster socket, IIRC most people make them from old 36mm dana 30 hub nuts welded to a 1/2 drive extension bar. Check that before doing it though, I'm not completely sure.

 

[streetxj]

Probably a 27 spline in 96 but you never know.

If you get an LSD for it, get a 29 spline one and put it in, then install 29 spline shafts and now you have a 29 spline 8.25.

Installing an LSD will require minor gear work, but it's a side adjuster axle, so no bearing pullers or shims or micrometers or presses are required. Might have to pay someone a 12 pack to get the new bearings pressed onto it (unless it comes with the old bearings in good shape and the races are still matched to the appropriate sides) and you'll need a dial indicator to set backlash back to what it was plus a torque wrench and a new set of ring gear bolts, but I think that's about it.

Basically, steps are:
take a gear pattern using marking paste, photograph it
measure backlash using dial indicator
remove axleshafts and carrier from diff, making sure to keep carrier bearing caps with the side they came from and properly oriented (they may already be stamped with markings to help with this)
remove ring gear from carrier (I forget whether they are left hand thread bolts, make sure before trying to unscrew them)
discard old ring gear bolts
replace bearings on new LSD carrier if necessary
install ring gear on carrier using new ring gear bolts
install carrier into differential
use side adjusters to adjust carrier location until backlash/pattern are the same as they were before, set carrier bearing preload, recheck backlash/pattern, torque carrier bearing cap bolts to spec, recheck backlash/pattern, repeat as necessary
install 29 spline shafts, cover, gear lube

and now you have a 29 spline LSD 8.25. Literally everything in the 8.25 except the carrier, spider gears, and shafts is exactly the same between 27 and 29 spline, so switching to an LSD carrier is the ideal time to upgrade the shafts as well.

I think the only truly custom/special tool (aside from the usual torque wrench/dial indicator etc) is the side adjuster socket, IIRC most people make them from old 36mm dana 30 hub nuts welded to a 1/2 drive extension bar. Check that before doing it though, I'm not completely sure.

Thanks for the info Kastein.

 

[Johnnie Walker]

strokedjeep.com bored TB about 100$. Most likely 8.25 with LSD is going to be 150$+ With your current mods, a bored TB should go well nicely. Might even improve MPG slightly. I know mine did.

 

[streetxj]

strokedjeep.com bored TB about 100$. Most likely 8.25 with LSD is going to be 150$+ With your current mods, a bored TB should go well nicely. Might even improve MPG slightly. I know mine did.

Thanks for the info Johnnie. My 96' already came with the 8.25. I took a closer look at it yesterday. Later on, I might install some sort of a locker. I just ordered a 62mm throttle body from Jeff (strokedjeep.com). I just made the payment today in the afternoon. It's 172 bucks which includes the 70 dollar core charge which will get refunded when he receives my stock throttle body. So when all is done, it would end up being 102 bucks, which is not bad at all. Looking forward to installing it.

 

[Johnnie Walker]

Yes, the 91+ XJ's came with a 8.25 unless ABS was equipped. Those had the Turdy5.
Since yours is a 96. before you swap a LSD carrier or locker, make sure you find out whether its 27 or 29 spline. Regardless, when you pull the cover I recommend installing lube locker gasket. Well worth the money and not having to spend time cleaning up gasket crap.
If you want it larger, I believe he will make up to a 65mm for no extra charge. Just have to let him know.