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Gearing: spline count and speedo gears


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Two questions:

 

1. Is there any way to look up or determine spline count in my D30 & D44 without pulling axles and counting? There is a set of 3.73s on FB Marketplace from a JK that the seller SAYS only had 5k miles on them before he swapped out. The D44 was a 30 spline and the D30 had 27 spline axles. Guy is asking $500 OBO. Good price?

 

2. Need to change my speedo gear. I have a 231 transfer case, do I need the short shaft gear or long shaft? I'm thinking the short shaft but need confirmation. Yes I could pull the current one to confirm, but it's been 30* in the evenings lately! LOL

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4 minutes ago, Green Mesa XJ said:

Sorry I can’t see what year your MJ is. If it’s 87-90 I believe it a long shaft gear. I think it switches to short in the 91-92 years and electronic speedometers.

But you might be able to use either if the cable reaches the gear correctly


Sent from my iPhone using Tapatalk Pro

 

Mine is an '88

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2 minutes ago, HOrnbrod said:

Yep, Dirty's right - missed the JK D44 part....

 

May or may not work - not worth it..

 

It works, but you need to enlist the help of Carl Jantz at Jantz Engineering (I think is what he calls his business) to do the correct machining and provide you with the needed bearings.  He's a master of stuffing the wrong gears in the wrong housings (D50 gears in D44 housings, D70 or D80 gears in D60 housings, etc), and there is some good reasons to do this.  I believe he said that on paper the JK D44 geatset is 20-30% stronger than a conventional D44.  The D50 gears nets an even larger gain, something around 40% better, but that's only for front HP applications.  So if you're trying to build something high zoot and light weight, yeah, or trying to stay within class rules for competition, sure, but for the regular guy... No.

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3 minutes ago, HOrnbrod said:

Good info Dirty.

 

Would still like to know Wahoo what gear ratio are you now, and what gear ratio you are planning on going to...

 

Replied to your post above........factory 3.54s are in the truck now, the ones I was asking about were 3.73s. When the time comes, I'll look for 3.73s or 4.10s. Doesn't seem too bad with the 3.54s now, so I was thinking 3.73s might be a good compromise compared to going to 4.10s

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If you go from 3.55 to 4.10, both axles cross the carrier break.

3.55 to 3.73, only the D30 crosses.

 

I went from 3.55 to 4.10 using "thick" gears on the D44. On hindsight, I think today I would have liked 3.73 more to get a little better mileage on the interstate.

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1 hour ago, HOrnbrod said:

If you go from 3.55 to 4.10, both axles cross the carrier break.

3.55 to 3.73, only the D30 crosses.

 

I went from 3.55 to 4.10 using "thick" gears on the D44. On hindsight, I think today I would have liked 3.73 more to get a little better mileage on the interstate.

 

Even though my truck does not see the interstate that much, that's exactly why I was thinking 3.73s also. 

 

So I would need a new carrier for the D30 when I do this? 

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34 minutes ago, WahooSteeler said:

So I would need a new carrier for the D30 when I do this? 

 

Yes, because if you are regearing the D30, R&P ratios of 3.73 and numerically higher would require a new carrier. Or you could use "thick" gears like I did on my D44 to make up the height difference and save some $$. I used the thick gears so I could retain the Trak-Loc carrier I had. Works great. 

 

It's all explained pretty well HERE.

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5 minutes ago, HOrnbrod said:

 

Yes, because if you are regearing the D30, R&P ratios of 3.73 and numerically higher would require a new carrier. Or you could use "thick" gears like I did on my D44 to make up the height difference and save some $$. I used the thick gears so I could retain the Trak-Loc carrier I had. Works great. 

 

It's all explained pretty well HERE.

 

Thanks for the good info, thick gears it will be on the D30. I have the Trak-Loc on my D44 also, but I'm still good with my stock carrier since I currently  have 3.54s, correct? Or will I need thick gears on the rear also? Just making sure....... 

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3 minutes ago, WahooSteeler said:

I have the Trak-Loc on my D44 also, but I'm still good with my stock carrier since I currently  have 3.54s, correct? Or will I need thick gears on the rear also? Just making sure....... 

 

Carrier break on the 44 is 3.92 & up, so UB fine going to 3.73. 

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23 hours ago, DirtyComanche said:

JK GEARS ARE NOT THE SAME!

 

You can put JK gears in early housings but you do NOT want to go down that rabbit hole.

 

A D30 isn't always a D30 and a D44 isn't always a D44.   These model numbers no longer mean anything.

 

Dirty, just to further educate me and clarify, does this include if the gears are with the full assembly, i.e. carriers, spider gears etc?

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17 minutes ago, WahooSteeler said:

 

Dirty, just to further educate me and clarify, does this include if the gears are with the full assembly, i.e. carriers, spider gears etc?

 

No, you can't just bolt them in even if you have the carrier.

 

The pinion is larger and takes different bearings.  The carrier isn't the same width, and also different bearings I believe.  Hypoid offset is the same, but the cut of the gears is so different that the carrier offset changed, and the ring gear is also no longer 8.5" (I want to say it's 8.66" or so).  Like I said, it can be done, but it's custom machining from the mad scientist Carl Jantz.  The axles have very little in common beyond their name and outward appearance. 

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6 minutes ago, DirtyComanche said:

 

No, you can't just bolt them in even if you have the carrier.

 

The pinion is larger and takes different bearings.  The carrier isn't the same width, and also different bearings I believe.  Hypoid offset is the same, but the cut of the gears is so different that the carrier offset changed, and the ring gear is also no longer 8.5" (I want to say it's 8.66" or so).  Like I said, it can be done, but it's custom machining from the mad scientist Carl Jantz.  The axles have very little in common beyond their name and outward appearance. 

 

Cool, thanks for the additional education. 

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