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Upgrades About to Begin

1K views 13 replies 4 participants last post by  AgingJeepster 
#1 ·
I've driven this 98' TJ for 10 years now, so I guess the trial period has expired.
The only thing I did to it soon after I bought it (2006) was 31x10.5x15" Wheels & Tires and Bushwhacker Fender Flares.
I'm not a big off-road enthusiast, I've never been able to afford to break my daily driver. It's beginning to look a bit down-in-the-dumps with the plastic bumper corners all faded and it still has the dent in the front bumper from the previous owner. This is my 4th Jeep over the past 25 years or so and it's time for a bit of a make-over.
So I bought some SmittyBilt bumpers and a ProComp 2" lift kit. Hopefully tomorrow I'll be able to get the bumpers on, then I'll be waiting a couple weeks for help on the lift. Real soon we'll be looking at some new tires as well.
 
#4 ·
Honestly, I'd rather have Monroe parts store replacement shocks than Pro Comps. If you can return that lift I would recommend. Shocks are the biggest contributor to ride comfort and good v. bad will go along way toward making you happy with your setup. If you go over to the TJ Tech section, lifts like this and what people recommend get discussed all the time. You will have plenty of reading.
 
#6 ·
Contrary to standing advice, I went ahead and installed the Pro Comp lift kit anyway, but not without drama.
The buddy who volunteered to help me bailed on me, and my nephew's shop that I was hoping to use became unavailable at the last minute.

I started on the rear and didn't really have all that much trouble getting the first spring out. Taking out the passenger side revealed a totally rusted out spring perch. Had I been in my nephew's shop, everything I needed (including wisdom) would have been right there. Instead, the project came to an abrupt halt. I was pissed! (can I say that?). Off I went to the shop with photos in hand. We decided to fabricate new bases that would fit inside and could be welded into the existing perch. I ground out the centre portion leaving the original outer ring in tact to weld the new base to. I knew I couldn't weld to the axle so the existing perch was all I had to work with. It worked out alright, but not without much anxt.
The front was considerably easier, but I gotta say that was probably more a matter of heightened determination than anything else.

Now that I've driven it for a few weeks, the only difference I noticed is a little bit of growling from the change in angle of the drive shaft/u-joints. It bothered me at first, but I'm not too worried. I'm told it's the price you pay for the lift.

My last Wrangler was an 83'CJ and had a 90' YJ before that. Even with this Pro-Comp lift/shock kit, the TJ still rides and feels better than either of those previous Jeeps. I don't have anything else to weigh it against, but I don't believe the ProComp kit is really all that horrible.

Next time ...... I'll go looking for help & advice beforehand.
 

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#8 ·
Now that I've driven it for a few weeks, the only difference I noticed is a little bit of growling from the change in angle of the drive shaft/u-joints. It bothered me at first, but I'm not too worried. I'm told it's the price you pay for the lift.
I don't agree with this. Yes, a lift can create driveline vibes, but it isn't something you have to live or even should live with. That sound is things wearing out. And when driveshaft ujoints break or centering balls bind bad things happen - TC case cracks (lots of threads on this if you search), broken pieces of driveshaft continue to spin and flail around doing lots of damage, etc. There are ways to address the vibes and they should be done.
 
#9 ·
Don't live with the driveline vibrations, thats going to kill parts quick. When installing my adjustable control arms to get rid of my transfer case drop I had a vibration on a test drive (3-4 mile loop). When I got home I felt the pinion bearing, it was so hot you could barely touch it. After fixing it, the pinion bearing area of the diff is near ambient temperature after a short drive.
 
#11 ·
Driveline vibes come because the angle of the rear driveshaft after a lift exceeds the angular working parameters of the single u-joints (IIRC, high single digits). IIRC the tech section on Tow Wood's site has a lot more explanation of this if want to get into it.

The cheap way to address this is to reduce the effective lift that your driveshafts are seeing. This is done by spacing the transfer case down. Many low budget lifts come with transfer case spacers for doing this. That can be counterproductive though because it gives back belly clearance that you just created with your lift.

The better, but more involved and expensive, way to address it is by converting your rear driveshaft to a double cardan driveshaft. This requires doing a slip yoke eliminator to the rear of your transfer case, acquiring a new double cardan driveshaft and using adjustable rear control arms to set the pinion angle on your rear driveshaft. With the OEM driveshaft the ideal pinion angle is parallel with the transfer case output so that the two single u-joints see the same angle and their irregular rotation offsets each other. With a double cardan driveshaft you want the double cardan joint seeing all the angle and the remaining single u-joint seeing no angle so the proper pinion orientation at that point becomes the pinion inline with the rear driveshaft. Again, materials on TW website in the tech section with nice pictures and everything on this.
 
#14 ·
So here I am, 9 months later and I finally solved my drive-line growl issue.
Whew!! Why did it take me so long when it was so darn easy?
I cut 6 pieces of 1 1/2" heavy wall (.135) square tubing. The inside had to be ground out a bit on one end to accommodate the locator pins/washers on the frame, and I also cut off the bevelled end of 6 old lug nuts to act as locators. This bevel worked great, fit right back into the original bevel on the skid plate.
I lowered the skid plate/transfer case enough to grind out a bunch of old rust, then positioned the spacers & bolted everything back together.
Drives & sounds like it should.
Thanks again for the suggestions and help.
 
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