Stock Rear Axle Ratios? Auto vs. Manual

Sorry, I did a Search and could not find anything definitive.
This is the only thing I've found.

Gearing
3.07 - used with 4.0L engine / manual transmission
3.31 - only available on older (pre87?) 2 door XJs with "Fuel Economy" package
3.55 - used with 4.0L engine / automatic transmission
3.73 - found in some XJs with the towing package
4.10 - used with 2.5L engine usually, and older XJs with the "Off-Highway Vehicle" package.

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I'm trying to find out the stock axle ratio for a '95 Jeep XJ w/ 2.5L I4 with the AX-5 Trans and the 30RH Trans. Are they both 4.10? I haven't jacked up the rear of my XJ w/ AX-5 to find out for sure (its an SE with NO TACH), but driving it "FEELS" like a 4.10 rear end.

I'm considering a swap from a manual trans to an auto trans, and need to know if I have to swap axle ratios as well.

The AX-5 has a 0.85 5th Gear, while the 30RH (3spd) has a 1.00 3rd Gear, I would "THINK" that the auto came with a taller rear axle ratio to match the shorter top gear of the 3spd auto. Anyone know for sure?

I don't see any real reason to change from 4.10's (I'm inclined to think that's what you've got) or 3.73's just because you're going to an automatic - you'll probably come out ahead anyhow.

Easiest way to do it is to count the pinion gear teeth, if you take the cover off. Here's the list:

14/43 = 3.07
13/43 = 3.31
11/39 = 3.55
11/41 = 3.73
10/41 = 4.10
9/41 = 4.56

I don't recall the applications, but there are only two 11-tooth pinions - a quick ring gear count (if you have 11 pinion teeth) should differentiate the two. These gear counts are for, of course, stock D35 ratios.

5-90

In the past, I've just marked the tires and axle yoke and with the rear wheels in the air and trans in nuetral, just turned the drive shaft and counted the turns of the yoke to get one full rotation of the tires.

You can tell the difference between a 1/2 and 3/4 of turn, so a little more than 4 turns of the yoke, but well less than 4 and 1/2, I got a 4.10, 3 and 3/4 turns of the yoke its a 3.73, 3 and 1/2 turns of the yoke its a 3.55, etc.

Often an Open differential will still turn both wheels in unison if there is no other resistance, if it doesn't, then I guess I'm stuck with pulling the axle cover and counting teeth.

Don't forget:

2.5L + AW4 = 4.56's.

JIM.

if your lucky the tag might still be there on 1 of the axels.

ILLXJ said:

Don't forget:

2.5L + AW4 = 4.56's.

JIM.

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You're kidding right? There were 4.56's available but I don't believe they ever came with this setup.


The 5 spd 4 bngr should be 4.10's.

the auto 4 bngr should be 3.73's.

043500 said:

You're kidding right? There were 4.56's available but I don't believe they ever came with this setup.


The 5 spd 4 bngr should be 4.10's.

the auto 4 bngr should be 3.73's.

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yes they did and I have the 4 banger flex plate, torque converter and bellhousing to prove it.......

Thanks Guys,
Its a 2WD, so only a rear axle, it makes finding donor vehicles even more difficult, since 2WD 4Cyl Auto's are pretty rare. I've already looked and can't find any tags on the Chrysler 8.25" rear axle.

I've looked in the '94-'96 Factory Parts Catalog, and they are only showing a 3.07, 3.55 and 4.10 as replacement ring & pinion for this axle.

Consider the top gear for the AX-5 is 0.85 OD, and its 1.00 for the 30RH.

0.85X4.10=3.485

I'm inclined to believe the 2.5L I4 w/ 30RH came with a 3.55 axle ratio.

My '95 XJ with the 2.5L and AX-5 cruises very nicely at highway speeds, including the typical speeding 70+mph. I'm guessing swapping to a 30RH, would require a swap of the ring & pinion gear to a 3.55 ratio to keep that comfortable cruise.

I'd like to just set it up like the factory configuration, I just can't find what that factory configuration is.

I'll have to find a donor car and figure it all out, unfortunately the only one I've found so far is a 2 hour drive away.

What about just leaving the axle in place, do the tranny swap, then see how you like it? Autos generally get slightly deeper gears than sticks, so I'm not sure why on earth you would want to go the other way.
Jeep on!
--Pete

Pete M said:

What about just leaving the axle in place, do the tranny swap, then see how you like it? Autos generally get slightly deeper gears than sticks, so I'm not sure why on earth you would want to go the other way.
Jeep on!
--Pete

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Yea, I'm considering that as well, but this is going to be a street vehicle, grocery getter, so fuel economy and comfort would be preferred over performance. Maybe the 4.10 would work fine, but I calculate 3483 rpm to cruise down the highway at 70mph. Maybe that would feel fine, maybe the XJ will feel like its huffing and puffing too much, as well as mileage. A 3.55 rear axle would give 3016 rpm at 70 mph.

Perhaps the thing to do, is as you suggest, do the swap, see how it works with the 4.10 gears. I don't like it, then the next project is to swap in 3.73 or 3.55 gears.

The cost of swapping gears would take many MANY years to repay in theoretical gas saved. If you want to save gas money, drive 60, not 70. :laugh3:
Jeep on!
--Pete

5-90 said:

Easiest way to do it is to count the pinion gear teeth, if you take the cover off.

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No, the easiest way is to read the little tag on the diff. :} Look at near the cover bolts on the drivers side. Should still be there assuming it got replaced if the cover was previously pulled.

If that's missing, read the BOM number off the right-side tube. Should be a number like 605730-2 which you can look up at the Dana site http://www2.dana.com/expert/wc.dll?DSD~deabill~4~ . That will at least tell you what it came with from the factory.

With that said, I would recommend against you trying to swap in an auto. Not to sound rude, but if you can't figure out what axle ratio you have, you might be in over your head doing a tranny swap as it's somewhat involved. You'll be swapping driveshafts, maybe the xfer case if the spline counts don't match, and dealing with a tranny/engine computer.

Besides, the Chrysler-made 30RH is a turd and most people are trying to swap in a manual after the auto lets loose. Simplest and most painless solution is sell what you have and buy what you want.

ILLXJ said:

Don't forget:

2.5L + AW4 = 4.56's.

JIM.

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Not much chance of finding an AW4 on a 2.5l since the AW4's integral bellhousing won't bolt up to the 4cyl engine.

Doesn't look all that integral to me?

"Yes, but..." I'm going to go out on a limb here and presume he doesn't have the tag anymore - the ratio on the tag actually LOOKS like an axle ratio.

I took mine off, and attached them to the "service keys" I keep in the garage. A "service key" set for me is:
Door key
Ignition Key
"Dog Tag" (name, model, engine, transmission, tcase, axles, gears, VIN)
All axle tags (including the LSD tag on the second 89!)
A "bolt snap" so I can clip them to a belt loop while I'm working.

I also have a copy of the "Dog Tag" on the vehicle's notebook - detailing mods and upgrades. What I used, what was the donor, how I rearranged it and why - all that sort of thing. Right down to wiring diagrams for additional power distribution I've added, and stereo installs. Even if I'm never going to sell the thing, I keep records.

And, I have a copy of each "Dog Tag" on my everyday keys (there are a total of five - one for each XJ and one for me as well.) It makes it easier when I go for parts, if I have a handy reminder. Yeah, I paid for the tags - but the time they've saved is worth it! Having dog tags for myself also comes in handy - at least they knew who I was when I was lying dead on Highway 85 (for a few seconds, anyhow.) And, they knew my blood type - even though, by some miracle, I didn't need any!

I've also got "tune-up" part numbers written down, and I'm going to get a tag made for that so I don't have to look them up every damn time. Filters, plugs, cap & rotor - all on one or two tags to make my life just a little simpler. I do like Dog Tags for sorting and carrying stuff like this - and being able to get them made at the local Army/Navy store is a nice plus.

But, I digress. Like I said, I was assuming that he didn't have a tag (since he didn't mention it!) and counting the pinion teeth is a fairly good way to tell, since there are only two ratios that have the same number of pinon teeth in the D35 (from the factory.)

5-90

lawsoncl said:

No, the easiest way is to read the little tag on the diff. :} Look at near the cover bolts on the drivers side. Should still be there assuming it got replaced if the cover was previously pulled.

If that's missing, read the BOM number off the right-side tube. Should be a number like 605730-2 which you can look up at the Dana site http://www2.dana.com/expert/wc.dll?DSD~deabill~4~ . That will at least tell you what it came with from the factory.

With that said, I would recommend against you trying to swap in an auto. Not to sound rude, but if you can't figure out what axle ratio you have, you might be in over your head doing a tranny swap as it's somewhat involved. You'll be swapping driveshafts, maybe the xfer case if the spline counts don't match, and dealing with a tranny/engine computer.

Besides, the Chrysler-made 30RH is a turd and most people are trying to swap in a manual after the auto lets loose. Simplest and most painless solution is sell what you have and buy what you want.

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Pete M said:

Doesn't look all that integral to me?

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Doh! Not sure what I was thinking. I have two vehicles with AW4s and one of them I just swapped in an AW4. You'd think I would have remembered that.

I also googled and found a few folks with a 2.5l and AW4, so there is a correct bellhousing out there. I'd vote for the AW4 over the 30RH any day for reliability and plus the overdrive would be a close match to the AX5.

lawsoncl said:

With that said, I would recommend against you trying to swap in an auto. Not to sound rude, but if you can't figure out what axle ratio you have, you might be in over your head doing a tranny swap as it's somewhat involved. You'll be swapping driveshafts, maybe the xfer case if the spline counts don't match, and dealing with a tranny/engine computer.

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Not to sound rude in reply, but I'm more than capable of doing a tranny swap, I've removed and re-installed several transmissions, as well as rebuilt engines. If you read more carefully, you'd see I've never asked what my axle ratio was or how to figure it out, I was inquiring about the axle ratio of a 4cyl automatic from the factory.

My limiting factor is budget, which will depend on finding a junkyard donor to pull all the necessary parts, and needing to swap axle ratios starts to cut into that as well. I'm well aware of the multitude of minor changes that pile up between the two different configurations, thus a junkyard donor to scrounge up all the little different parts. Even with a junkyard donor cost can get out of control, that why I'm trying to figure out if I've got to swap axle ratios as well as everything else.

I have a Chrysler 8.25" Axle, the best I can tell, the DANA site doesn't have much info about the Chrysler Axle. Although, spline count was changed on the AX-5 output shaft sometime near my model year, so theres a chance that I'll need the slip yoke from the junkyard donor or even the whole driveshaft altogether, if length is different.

Like I stated previously, this is 2WD, so no transfer case to worry about. Yes, I'm well aware of the wire harness for the tranny, the PCM, cooler lines and the incompatibility between 4X2 and 4X4 configured trannies, pedals, shifters, etc.

I'm not overly excited about the 30RH, but from what I read, the AW-4 is nothing to get excited over either, besides its the OEM configuration for a 4 Cyl, which will be much easier to swap than improvising another swap. Its hydraulic as well, with no TCU to worry about. Besides, its a 2nd Car, for the kid to use also, it can easily sit for a couple of weeks while rebuild the 30RH if it goes out. I was planning on rebuilding the Junkyard donor before the swap anyway. I'll probably still have the AX-5 in the corner of the garage if it all goes to heck anyway.

I may be overly optimistic, I've found a junkyard with a jeep 30RH for $200 and willing to allow me to pick a part the donor car, but they may nickle dime for the other parts. Buts its a 2 hour drive away, so I'm still looking and hoping for something closer, because it may be several trips before I get everything together.

lawsoncl said:

Doh! Not sure what I was thinking. I have two vehicles with AW4s and one of them I just swapped in an AW4. You'd think I would have remembered that.

I also googled and found a few folks with a 2.5l and AW4, so there is a correct bellhousing out there. I'd vote for the AW4 over the 30RH any day for reliability and plus the overdrive would be a close match to the AX5.

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That is an intriguing thought. The TCU will talk to the 2.5L auto PCM?

As well the bellhousing pattern? Its different between the 2.5L I4 and 4.0L I6, I thought they were the same? Is it a depth thing?

Finally, Rebuilding? I've never done a Japanese Automatic, is that much different? Are the rebuild kits as available as the domestic automatics? What about the cost of the kit, japanese parts tend to be more expensive than domestic.

lawsoncl said:

Doh! Not sure what I was thinking. I have two vehicles with AW4s and one of them I just swapped in an AW4. You'd think I would have remembered that.

I also googled and found a few folks with a 2.5l and AW4, so there is a correct bellhousing out there. I'd vote for the AW4 over the 30RH any day for reliability and plus the overdrive would be a close match to the AX5.

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I wouldn't have posted if I didn't know for sure. I pulled the tranny & t-case about a month ago. The axle tags are marked 4.56 & I counted the gear teeth. JIM.

Rick Anderson said:

I've already looked and can't find any tags on the Chrysler 8.25" rear axle.

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Like I said guys, I've already looked for tags, they are gone.

I'm still in the middle of patching holes in the floor pan, and I've been distracted with fixing the shelves in our bedroom closet that fell off the wall, so I haven't gotten to figuring out the axle ratio.

There is a casting number on the carrier, correct me if I'm wrong, but I don't think that is going to tell me anything. I can't find any other numbers.

I still have to pull the rear drums, inspect the shoes/brakes and adjust the parking brake to prepare for the Maryland State Safety Inspection, I'll probably do that this weekend. While the rear axle is in the air, I'll figure out the axle ratio. I'll be surprised if its not a 4.10:1.