1990 xj 4.0 242 Hack n Tap question

[sjx40250]

I am sure this has been covered many times. If so, just reply with the link, if you can find it!

1990 XJ 4.0 with AW4/242 4" lift with OME springs. I have a front drive shaft from an 1989 same config and measures very close to 30 7/8 center to center u joints.
The rear drive shaft is installed but has a bit of a vibration, not much. It measures about 30"
The yoke in the T/C has moved out about 1/2."

Will a hack n Tap work? I read that it applies to 4 1/2" lift and more. What do you suggest?

 

[75SV1]

I can't quit decipher your info. I did do a HnT on a '98 with 4.5 lift. I had a 8-1/4 in it at that time. Actually, my lift in the rear was more like 6" as the RC springs were new. It took 2 years for them to settle to 4.5.
I had to cut the splines on the 231 TC to the recommended minimum of 1-1/8. So, I had about 1" longer measurement of the extended driveshaft than the measurement between the two yoke centers.
So, you could pull your rear driveshaft and take measurements. I will be doing a HnT on my 2" lifted 2000 XJ. I doubt a stock driveshaft will work. I might have one shortened or go with a custom.

 

[sjx40250]

The point I was trying to make was there is only a 7/8 difference between the length of the rear DS and the length of the front DS intended to replace it.

As a result of the 4" (measured) lift, the yoke has moved toward the back of the vehicle by about 1/2."

To my thinking, the FDS is only 3/8" too long.

Not having the RDS removed, I don't know how much T/C tail shaft engagement is left with the yoke moved 1/2."

I was wondering if I need to make any modifications of either the output shaft or the yoke to make it work.

75SV1 - Your example is good but there are two differences, the 4/5" lift+ and the 231 T/C which adds too many variables to assess how your situation applies.

 

[sjx40250]

Since I can't edit.
I meant to say modifications other than drill and tap to the new yoke.

which brings up another question. Why can't the existing yoke be modified? I the issue drilling the hole for the bolt?

 

[75SV1]

Let's start at the beginning. First, the 231 is irrelevant to this discussion. As you note, many variables. You are replacing a Slip Yoke with a fixed yoke. The output shaft is very long and will probably need to be cut. Also, you might need the seal kit for an older T/C case. I remember '95 and earlier being that.
There is some math needed and measurements. You need the extended length of the front axle you will use. Then minus 1" from that. Then add back the distance of the length from the HnT face to the ID shoulder. You could measure from the face to the fixed washer were the bolt head will be. For some reason 29.5 is in my head for the Extended length of the front driveshaft. And 1" for the other. So, 29.5-1" + 1" as an example. So, when all the cutting, drilling etc. and the HnT yoke is on the TC, the driveshaft's center of the ujoint can extend 1" past the center of the Yoke.
Since lifts and what axle you have vari, you need to measure the distance from the face of the yoke on the axle to the shaft of the TC case. For that you need to remove the current driveshaft. Put on you parking brake and also block the wheels. Don't ask how I know.
Then mark the '29.5' or whatever your measurements come up with. That is were you will cut the output shaft of the TC. You must or should have at least a 1-1/8 length of splines left.

 

[Evan03]

Ive checked run out on a few jeep driveshafts they are scarey like an inch with huge weights tacked on to prove it.

Not sure what I think about the hack n tap. Almost seems like a waist of a drill bit. Is likely a corner cutting method created by jeepers.

Just get a real sye and a good driveshaft thats straighter than what comes on jeeps

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[sjx40250]

Evan03 - My preference would by a SYE with DS. At this time it is not in the budget. The front DS is in hand. I am thinking that the Hack n Tap is better than what is running now.
Mostly a DD.

75SV1 - I think I understand. "distance of the length from the HnT face to the ID shoulder" is the dimension of the bottom end of the ID spine and the bolt surface. This dimension fills the dimensional gap between the end of the T/C shaft and the axle yoke.

To continue my understanding, the amount of variable length of the drive shaft through suspension movement should be 1" for compression. The amount of spline engagement with the yoke needs to be no less than 1 1/8"

[/url]TC output by Patrick Boulden, on Flickr[/IMG]

 

[Evan03]

How is a 4" lift in the budget but not the supporting mods to go with it.

I see a weight on your driveshaft if the front shaft your going to use is straighter that on its own might smooth it out some.

For what its worth I talk all this but I havent done a sye yet. Ill do the jb shorty when its time.
I found out jeep driveshafts arent that straight when I twisted my stock rear shaft all up.

I cut the ends off and made my own shaft with 1/4" wall 2.5" tube. I used a dial indicator to weld ends on straight as possible.
got it pretty straight after awhile tapping and tacking. Then decided to check a straight stock shaft my eyes nearly popped out of my head. Was like yup mines straight enough.

My driveshaft smoothed my jeep out alot and is pure beef.

I honestly think the hack in tap is okay if the front shaft is better than the rear it replaces but ive look at runout on them to and theyre not that great either.
But the cv joint may mask some vibrations
however
I would not be exspecting miracles from it.

That brings up u joints are they fresh and tight? If theyre more than a couple years old theyre likely asking to be replaced and could be causeing vibrations.
Ive installed and seen lots of ujoints installed improperly causeing vibrations.

New isnt always a good thing specially from the hack n tap cookie cutter jeep crowd


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[boncrshr]

I am sure this has been covered many times. If so, just reply with the link, if you can find it!

1990 XJ 4.0 with AW4/242 4" lift with OME springs. I have a front drive shaft from an 1989 same config and measures very close to 30 7/8 center to center u joints.
The rear drive shaft is installed but has a bit of a vibration, not much. It measures about 30"
The yoke in the T/C has moved out about 1/2."

Will a hack n Tap work? I read that it applies to 4 1/2" lift and more. What do you suggest?

Oddly enough, I came here to post a thread about this very topic. I have an 01 XJ with 4" IRO short arm kit. The rear has had an annoying vibration/harmonic since I installed the lift. This weekend I did the Hack and Tap from IRO. I used this install method and it worked great. Buy the jig they sell, it's worth it. Or I could mail you mine I guess.
https://www.youtube.com/watch?v=l022tVfPQ5s

The weird thing is that I had a vibration after I installed the kit. I had to shim my differential 3 degrees upwards towards the transfer case. I haven't read of anyone else mentioning this. It drives AWESOME now with no vibes whatsoever. I did swap out the D35 for an 8.25 when I got this Jeep, and I wonder if that was why it vibrated? Also, I don't have the front driveshaft in yet and I'm concerned it may vibrate.

 

[RCP Phx]

Hack-N-Taps are fine for "Mall Crawlers" but definitely the wrong choice for anyone that takes their wheeling seriously!

 

[75SV1]

Evan03 - My preference would by a SYE with DS. At this time it is not in the budget. The front DS is in hand. I am thinking that the Hack n Tap is better than what is running now.
Mostly a DD.

75SV1 - I think I understand. "distance of the length from the HnT face to the ID shoulder" is the dimension of the bottom end of the ID spine and the bolt surface. This dimension fills the dimensional gap between the end of the T/C shaft and the axle yoke.

To continue my understanding, the amount of variable length of the drive shaft through suspension movement should be 1" for compression. The amount of spline engagement with the yoke needs to be no less than 1 1/8"

[/url]TC output by Patrick Boulden, on Flickr[/IMG]

I would agree that a true SYE would be wise depending on the level of build and harshness of terrain you will see. Both of my present XJs are road going. I think the 'true' SYE for a 241 is $500, then the cost of a custom driveshaft. $500 too ??.
I think the question you ask, is yes the driveshaft need to be able to extend 1" forward for suspension travel. Also, 2-3" reward for suspension travel. I am going by the instructions from IRO. Also, as to those instructions the minimum length of the splines engagement is 1-1/8.
On my 2000 XJ, I will be swapping in a 241. Its a 2" lift. Some mainly DD, towing, and some rough gravel roads. Probably some fishing and hunting trials. So, a HnT should be OK. Never know, maybe I see I have extra $$. My next build, that's a different story. I might even spring for an Atlas.

 

[Tim_MN]

Hack-N-Taps are fine for "Mall Crawlers" but definitely the wrong choice for anyone that takes their wheeling seriously!

Not completely true. I was at Fall Fling in Moab three different times with a Hack & Tap SYE. It is true that H&T SYE success depends on the skill of the installer. Poor workmanship will cause less than ideal results, and less than ideal durability.

 

[sjx40250]

Given the this XJ was purchased new in 1990 and just got a lift, I doubt I will be seeing anything really serious. I would like to improve on the current configuration. If adding the H&T would improve the vibration (very small) and ensure proper engagement for the added height, I would be happy with it. Spend $1K is not justifiable when there are so many other issues that need to be tackled.
I finally swapped in the 245/70 - 16 from the 2000WJ which will be up for sale. Looks much better then the 225/70 - 15 that were on it.
In this case the ride is better and sitting a bit higher is an improvement.