Most efficient axle

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The Dark Side of Will
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Most efficient axle

Post by The Dark Side of Will » Sat Sep 04, 2010 8:56 am

I have a 1985 AMC Eagle wagon which I am building up to be a fun winter beater/light offroader.

The stock driveline consists of:
AMC 258 + Non-WC T5 + NP 119 T-case + 2.73 gears. The front diff is a Dana 30 center section. The rear is a Dana 35 with two piece axles.

I'm going to end up with:
Jeep 4.0 + WC T5 (Maybe a TKO if I can score a used one cheap) + NP 229 + 3.54 gears. I bought the front diff from a 4 cylinder Eagle to get the 3.54 front end. However, I have quite a few options for the rear.

I am NOT interested in another Dana 35. The stock ones in Eagles are worthless. My dad's owned a few and they all make noise. The wheel bearings are tiny and badly designed. I'm not even willing to try one with one piece axles.

The axles from Cherokees are easy to swap. I can have a Dana 44 or a Chrysler 8 1/4 pretty easily.

Of course with more work (welding on spring pads, relocating shock mounts, maybe narrowing) I could put basically any axle I want in it (e.g. GM 8.5")

What's the most efficient readily available axle on the market? I know a Ford 9" is pretty inefficient, which is why it's not on my list.

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Re: Most efficient axle

Post by iadr » Thu Sep 09, 2010 2:29 am

The Dark Side of Will wrote:I have a 1985 AMC Eagle wagon...I'm going to end up with:
Jeep 4.0 + WC T5 (Maybe a TKO if I can score a used one cheap) + NP 229 + 3.54 gears. I bought the front diff from a 4 cylinder Eagle to get the 3.54 front end. However, I have quite a few options for the rear.
Similar "clutch & back" drivetrain to what I'm doing, under a Suzuki Sidekick LWB.
The WC 14.7" 23 spline mainshafts are in very very short supply. PM me if you meed help there.
The OD ended up being a funny ratio, because the internal step ratio wasn't really like anything else because I chose Mustang 3.8V6 SN95 ratios. I ended up with the factory ".72" gears giving me .64.

If I had to do it again I'd probably use a RSG Terminator which is an AX14 with Toyata Supra guts.
I'm using a NP129 turned upside down to give a PS drop. The Suzuki Diffs use crazy 5.125:1 ratios. I've found a set of 3.73 gears can be sourced from a Samurai & that'll go in the front. I think it's going to get a 3.73 8.8 from an Explorer in the back, just because they are very decent pieces. So !@#$ heavy, though..

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Re: Most efficient axle

Post by crazyman » Thu Sep 09, 2010 2:56 am

Whatever you can get a Zexel Torsen/detroit trutrac into.

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Re: Most efficient axle

Post by SilverXJ » Fri Sep 10, 2010 6:52 pm

crazyman wrote:Whatever you can get a Zexel Torsen/detroit trutrac into.
They make them for the 29 spline 8.25, which is a strong axle for the vehicle.

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Re: Most efficient axle

Post by SilverXJ » Sat Sep 11, 2010 10:35 pm

Also, the 8.25 axle can be easily converted to disc brake using parts from a 93-98 Jeep Grand Cherokee. If you do go with the 8.25 get a 97+ as it will have the 29 spline shafts. I wouldn't go with a Cherokee D44 as they fetch a premium price and the 8.25 is just as strong as the D44 and will survive well behind a 4.0L or stroked 4.0L.

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Re: Most efficient axle

Post by The Dark Side of Will » Sun Sep 12, 2010 11:41 am

Thanks for all the input!

I've been in touch with the guy at www.5speeds.com who says that the WC and non-WC output shafts use the same alloy/heat treatment and are dimensionally identical EXCEPT for the forward tip, which runs in a bushing in the input shaft for non-WC transmissions and a needle bearing in WC transmissions. Apparently, turning a non-WC output shaft into a WC output shaft only requires some simple lathe work, which I am prepared to do.

I'd like to run the 2.95 first gear instead of the 3.79 or similar stock first. This basically means I'm limited to Mustang or Camaro V8 gearsets. I do want the tallest 5th I can get also, which is (I think) 0.62. The 3.54*0.62 will give me a 2.19 overall 5th gear, while the stock 2.73*0.81 has a 2.21 overall 5th.

However, since a manual transmission AWD car ALWAYS tempts me to drop the clutch from the far side of the tach, I'd really like to score a used TKO instead of sinking much money into a T5.

Back to axles:

As far as Torsens/TrueTracs go, I'm more interested in lockers. I'm fine with leaving the diffs open for driving around corners on pavement. This is not a road course car. If I'm in mud or deep snow, I want a locker more than a limited slip anyway.

I went to a local yard and found three 3.55 8 1/4's from mid-90's Cherokees. What spline count did those axles have before they had the 29 spline shafts? How much weaker were the earlier axles? I'm looking at a 2+ hour drive each way to grab a '97+ axle.

The spring pads measure about 43 3/8" C-C with the tape going over the pumpkin. This is the same as the Eagle axle. A hub width of just over 61" matches also. The shock mounts even look VERY similar between the two axles.

The yard also had a '98 GC D35 with disks. The manager wasn't willing to split it, but another yard nearby lists the calipers. I can probably get all the disk parts from them.

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Re: Most efficient axle

Post by SilverXJ » Sun Sep 12, 2010 2:13 pm

The Dark Side of Will wrote: I went to a local yard and found three 3.55 8 1/4's from mid-90's Cherokees. What spline count did those axles have before they had the 29 spline shafts? How much weaker were the earlier axles? I'm looking at a 2+ hour drive each way to grab a '97+ axle.
Earlier ones are 27 spline. I don't know the strength numbers though.
The yard also had a '98 GC D35 with disks. The manager wasn't willing to split it, but another yard nearby lists the calipers. I can probably get all the disk parts from them.
You will need calipers, mounting brackets, backing plates, soft hoses to attach to the hard line, and parking brake hardware. You may also need the axle flange studs and wheel studs. Here is a writeup on putting ZJ discs on a XJ D35. Same thing for an 8.25 but you need to open up the bracket hole a bit. Can be done with an air grinder. http://jeep.blackonyx.net/pdfs/zjreardiscs.pdf

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Re: Most efficient axle

Post by The Dark Side of Will » Sun Sep 12, 2010 6:16 pm

As long as the 29 spline axles ARE stronger, that's fine. I don't need to know how much. Do you know the relative diameters?

Thanks for the link to the writeup! I knew I'd need all of that stuff, except that I hadn't thought about the studs.

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Re: Most efficient axle

Post by SilverXJ » Sun Sep 12, 2010 6:36 pm

Chrysler 8.25 - 27 spline, 1.17" diameter shafts, 8.25" ring gear, 3" axle tube - used 91-96
Chrysler 8.25 - 29 spline, 1.21" diameter shafts, 8.25" ring gear, 3" axle tube - used 97-01

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Re: Most efficient axle

Post by The Dark Side of Will » Sun Sep 12, 2010 7:36 pm

Awesome! Thanks!

Did you copy that info from a listing someplace?

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Re: Most efficient axle

Post by SilverXJ » Sun Sep 12, 2010 8:24 pm

Yes, got it off NAXJA

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Re: Most efficient axle

Post by The Dark Side of Will » Sun Sep 12, 2010 11:05 pm

Google tells me: http://www.naxja.org/forum/
Sweeet. It's nice being in a big community for once.

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Re: Most efficient axle

Post by The Dark Side of Will » Tue Sep 14, 2010 3:48 pm

I guess the OCD Perfectionist in my won't let me get the 27 spline axle when there's a 29 available.

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Re: Most efficient axle

Post by SilverXJ » Tue Sep 14, 2010 7:34 pm

Of course not! And there is no reason to. I got my 8.25 for $150 a few years go to replace my D35.

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Re: Most efficient axle

Post by The Dark Side of Will » Wed Sep 15, 2010 6:05 am

I'm looking at $75 +4-5 hrs drive time for the 29 vs $150 +1 hr for the 27.

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