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I just can't figure out the logic behind this thing...why??? All you're doing is sliding a small wheel to either join the inner and outer axle, or to leave them seperated. WHY??

So, to put your YJ into 4wd, you pull your t-case lever, which engages the front driveshaft and it also activates this vacuum thing to engage your right front tire. Is that the general idea? Am I missing something?

Why can't you just have a solid axle in there? Like a tj... I've heard you can put a TJ shaft in there...not really sure how the seal's work on that, but that's not the issue at hand.

Why have the vacuum???
 

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Less wear on parts when not on 4x. This allows for less rotation of the driveshaft as the differential can spin the disconnected shaft instead of the driveshaft.

I've heard same year XJ parts will work and all you have to do is cover the gaping hole in the axle tube.
 

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One of my friend Ray owns a driveling shop ( Cochise Driveline) and them solid shaft 30’s keep him in business, (I’m exaggerating but you get the point). The carrier bearings go out on them really fast. He changes at least two a Mont.
 

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why would the carrier bearings go out that quick if it was a solid axle. I understand there is less wear, but doesnt the rear axle get the same amount of wear constantly as a Tj without a vacuum disco?
 

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Originally posted by Qbert:
<STRONG>One of my friend Ray owns a driveling shop ( Cochise Driveline) and them solid shaft 30’s keep him in business, (I’m exaggerating but you get the point). The carrier bearings go out on them really fast. He changes at least two a Mont.</STRONG>
<IMG SRC="smilies/confused.gif" border="0"> Mee too? If the bearings wearout that shouldn't have anything to do with the shaft spinning free or not!
Bearings will wear out if you drive around on dry ground in 4 wheel drive and put all kinds of strange forces on them. I never heard of a 30 bearing wearing out. Are you sure?
 

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It's all in the gas milage. More thins to spin means more drag. <IMG SRC="smilies/eek.gif" border="0">
 

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I'm not Bsing you guys wy shuld I? I see it very ofthen they get pited and make a huming noise. so they bring them in to see waht the hell it is and thats wat hapens. I dont know wy I just see the result.
 

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I welded my friends up.. Now its one piece.. that 2-peice design is the biggest piece of shit setup ever. just weld it!
 

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go one piece or disassemble and reassemble in the "always engaged" position.
 

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I read the Mfg did this to prevent wear on the diff. Some GM's even have this sort of set up with a different kind of motor. I have an XJ with this damn vacuum thing. One day I flexed a little to much (if that's possible) and pulled the vacuum lines off of the diaphragm. Lost 4WD for the rest of the day and made one interesting day in 2WD.

Best thing to do, get a axle shaft from a Select-Trac and D30, they were one piece. Only the Command-Trac's had a two piece. Put the new shaft in and cover the hole where the vacuum motor is.

You could always get a 4x4 Posi Lok for $200 to make the vacuum a manually operated motor. This would work good if you have a locker in the front and want to disengage for some reason...to prevent wear on the road?

Anyway, I pulled that motor, slide the fork into the engaged position and then capped the vacuum line valves, keeping the diaphragm in place and keeping the axle engaged at all time. I have this funny rattle though, thought the fork was worn. I rebuilt the motor with the new fork and it got worse. Gonna pull it again tonight.
 

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The D30 carrier bearings are smaller than the D35/44 in the rear of the TJs and will not put up with full time spinning for as long.
The best way to get rid of the vacuum disco is the new vacuum disco eliminator kit.
Kit includes your choice of Dana 44 OR Dana 60 front end, WITH manual hub lockouts, and matching Dana 60 rear, in either full float or 35 spline semi-floater varieties <IMG SRC="smilies/biggrin.gif" border="0"> <IMG SRC="smilies/thefinger.gif" border="0">

Works well with the new slipyoke eliminator kit, available with either a D300, or Atlas t-case, AND the new fuel injection bolt on kit(LT1) <IMG SRC="smilies/biggrin.gif" border="0">
 

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Originally posted by Robert:
<STRONG>The D30 carrier bearings are smaller than the D35/44 in the rear of the TJs and will not put up with full time spinning for as long.
The best way to get rid of the vacuum disco is the new vacuum disco eliminator kit.
Kit includes your choice of Dana 44 OR Dana 60 front end, WITH manual hub lockouts, and matching Dana 60 rear, in either full float or 35 spline semi-floater varieties <IMG SRC="smilies/biggrin.gif" border="0"> <IMG SRC="smilies/thefinger.gif" border="0">

Works well with the new slipyoke eliminator kit, available with either a D300, or Atlas t-case, AND the new fuel injection bolt on kit(LT1) <IMG SRC="smilies/biggrin.gif" border="0"></STRONG>
OK, and for cheap lazy ass bastards like myself with piddly little rigs, I'll stick to a $1.99 pack of vacuum valve caps and some washers. <IMG SRC="smilies/biggrin.gif" border="0"> <IMG SRC="smilies/biggrin.gif" border="0"> <IMG SRC="smilies/biggrin.gif" border="0">
 

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...but Robert, I am pretty sure that the carrier berings are the same size b/t the TJ 30 and YJ 30. So whats the big deal?
 

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The TJs DO NOT have the vacuum disconnect in the front end, therefore, the axles, ring and pinion, carrier, d-line, and t-case components all spin at road speed.
Chrystler got rid of the vacuum disco because it was problematic. But in doing so they started wearing out front end components, chipping into fuel economy, and increasing the possibilities for vibrations in the front end.
The YJs with the disco, only spin the left side axle shaft full time, and most of that rotation is lost in the differential side gears. The carrier does not spin as much(if at all) as compared to the TJ front end.

I know there were other changes in the D30 from the YJ to the Tj, besides the disco delete. DC went to a standard cut R&P, and they went away from the crush sleeve design on the pinion gear.

But no matter what they do to the Dana 30, it is still easy to weld a chain to it for its real purpose in life......as a boat anchor <IMG SRC="smilies/laughing.gif" border="0"> <IMG SRC="smilies/laughing.gif" border="0"> <IMG SRC="smilies/laughing.gif" border="0"> <IMG SRC="smilies/laughing.gif" border="0"> <IMG SRC="smilies/biggrin.gif" border="0"> <IMG SRC="smilies/thefinger.gif" border="0">

[ 09-08-2001: Message edited by: Robert ]
 
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