I recently finished my Hagen rear diff over rotation, and now am installing a new t case with 4 2 1 gears in the low range. I did get a chance to drive the Tracker a bit before I began the t case swap and noticed a vibration when I begin to accelerate away from a stop. It only occurs for the first few feet of acceleration, then smooths out fine. I was also smelling gear oil occasionally, and when I got around to removing the old t case i saw the output flange seal on the rear was leaking, slinging oil around the tunnel. Now, it wasn't leaking before the overotation, so I'm wondering if changing the driveshaft angle could cause this? The vibe has got me concerned as well, as I don't want to continue wasting seals, and possibly ruin an output shaft. One thing I neglected to do was mark the flange position in relation to the rear and front diff flanges, so there's a good possibility there not located in the same position the came off . So, any ideas where I can start looking for the source of the vibe? Did a search, in conclusive. Lots of info for Sammies. One more thing, I'm having to swap yokes in the rear driveshaft to accomodate the different spline count of the later model t case, and the yoke I got had some minor rusting on the outer sliding surface. I'm thinking I can polish this out without a problem, but if not , anyone got a driveshaft yoke in good shape for a 97 Trackick?

OK, I think I may have answered my own question. After doing some research and looking at the sites  Driveline basics with Steve Johnson, and Tom Woods Custom Driveshafts, it seems that according to them , pionting  the rear pinion directly at the t case output, as in the Hagen rotatioin, causes the u joints at the rear of the driveshaft to be out of alignment with the front. According to both sites, to avoid vibration, as well as premature failure of the  u joints, output shaft bearings, seals etc, when changing the driveshaft angles and ending up with u joints in non equal angles , such as in the Hagen overotation, the only way to eliminate vibes is to utlize a double cardin type joint at the front. sNow my question is : Of all you guys that have done the Hagen rear rotation, what problems did you experience with driveshafts, vibes, etc, and how did you solve the driveshaft problem?  Has anyone converted to a double carden style front joint? where did you get this done? Help is needed for sure. Thanks, don't want anymore BENTPARTS!

what you researched is correct, but remember tho that the rear driveshaft has a slip yoke at the tcase. So, with the ujoints are out of alignment, the slip yoke will slide back and forth a bit (this doesn't occur when the ujoints are in alignment). If you don't have a slip yolk, then yes this sort of mod would need a cardin.

I suspect what may be happening in your case is that between the spring lift and the axle rotation, your slip yoke is pulled further back from the tcase output.

I've not done the rotation yet, but I notice that just a sping lift moves the slip yolk back about 1/4". I'm gunna measure the change when I do the axle rotation and determine is a driveline spacer will also be needed to keep the slip yolk properly enguaged (aka not bind a full compression yet not extend too far at full droop).

Thanks, Snofalls, I considered that also, the need for a spacer that is. When I first did the spring lift, it was the original OME /RR lift with a 1" coil spacer in the rear. Since then I've raised both front and rear about 3/4" more. I did make up a driveshaft spacer for the rear, about 1/2" thick. It worked fine         ( before the rotation) but after the rotation I figured I needed a bit more, due to the angles and such. Maybe I had it backwards,  and installed a 3/4" driveshaft spacer and it's too much now. I'll have to check everything again once I put the t case back in. Mr. Hagen , care to chime in?
 

The rear diff is not suppose to point at the t case. Its suppose to point higher than the t case. You want to get the u joint at the rear diff to be the same angle as the t case. So if the tcase joint has 2 degree angle you want to over rotate the rear joint to 2 match.

The rear diff is not suppose to point at the t case. Its suppose to point higher than the t case. You want to get the u joint at the rear diff to be the same angle as the t case. So if the tcase joint has 2 degree angle you want to over rotate the rear joint to 2 match.

Oh really !!!! I was under the impression it pointed directly at it ...
looking at the pic in the writeup I see

that *looks* like it's pointed straight at the tcase, but probably just the angle the pic was taken from.

thx mike, getting it "over-rotated" to where angles are equal makes total sense (and relieves the fears I had about relying upon the slip yolk to contain the "vibe")

Here is a paint pic I just did up quick

Quote from: Mikerpm4x4 on November 28, 2007, 09:17:50 AM

The rear diff is not suppose to point at the t case. Its suppose to point higher than the t case. You want to get the u joint at the rear diff to be the same angle as the t case. So if the tcase joint has 2 degree angle you want to over rotate the rear joint to 2 match.

Oh really !!!! I was under the impression it pointed directly at it ...
looking at the pic in the writeup I see

that *looks* like it's pointed straight at the tcase, but probably just the angle the pic was taken from.

thx mike, getting it "over-rotated" to where angles are equal makes total sense (and relieves the fears I had about relying upon the slip yolk to contain the "vibe")

The angle of the rear joint isnt as clear as I would have liked. The rear joint has just slightly less angle because when your on the gas the torque will raise the pinion up slightly from bushing give.

Mike

OK, I think I understand now. If I do, It is the angles in the bottom diagram I'm shooting for. That's pretty close to what I now have, and when I finished the rotation I thought I had done something incorrectly. Now I'll measure the angles at both ends once I have the t case in , and try and get them equal, by adding/removing spacer thickness under the  rear center link, correct?

bentparts, I suspect with the added spacer you're now getting the slip yolk to bind just a bit (adding that vibe during acceleration). I'd bet you remove the "extra" spacing you did and the vibe you see at launch will stop.

I'm also hoping that the rear tcase seal isn't now FUBAR'd 

Be sure to let us know how it works out.

Is there any chance you could post some pics? A pic is worth a 1000 words.

I'll get the pics as soon as I get the t case back in and the driveshaft bolted up. I'm still waiting on a couple of parts, twin stick boots and new seals for the t case I got from Stan. ( want to start with fresh ones to be sure) I'm pretty sure the rear seal in my old case is shot, it was puking gear lube and flinging it around the tunnel. I will re check everything, driveshaft spacer, and angles, once it's together and shoot some pics. I tried to take a picture of the new slip yoke with the bit of surface rust, but all I got was a bad reflection, no detail. I was able to get the surface cleaned up, now I'll try polishing it to smooth it out. Thanks Guys,  appreciate the help!

Here is a paint pic I just did up quick

It all makes sense now.  I remember reading someone saying "point the pinion towards the t-case" but it never sounded right to me.

How do you fill up the diff with the right amount of oil so as not to starve the pinion bearing?

Apparently, you are supposed to overfill it somewhat, to insure enough lube getting to the pinion. That's what I've read anyway.

OK, cue the twilight zone theme, the vibes are gone. I've still got to get some photos of the completed install, but a test drive had me scratching my head. After I got everything put back together, I installed the drive shaft with my homemade 1/2 " driveshaft spacer. Took it out for a test drive, and Vibe city! This time, it shook all the way thru 30mph and on. I was a bit freaked out, thinking maybe the used transfer case was gonna be a problem, but I wanted to check the u joints first. I had to swap out the front yoke to make the d/s fit the newer model t case, so maybe I screwed up there? NO dice, after removing the driveshaft, both sets of joints were smooth and free. I did a couple of measurements, and again, there was almost 2.5" of travel in the sllip yoke, so I went back to the bigger d/s spacer. This one was a professionally made aluminum one from RR. bolted everything back up, viola, smooth as glass! The spacer I made was not lathed turned, and was surley not perfectly round. I probably just got lucky the first time I used it, getting it centered. NO more shaking on roll out, or anywhere for that matter. Low range is insane with the 4 2 1 gearing too. Can't wait to test it. The dana twin stick boot worked great after making a new plate to attach it to. I used a piece of rubber sheet to attach the trimmed dana boot to, glued them together with rubber cement and let 'em cure for a day. I may extend the sticks a bit. Photo's to come later today.  BTW. MikeRPM, Question: How do you now fill the rotated rear diff? I jacked the rear of my Tracker up as high as I could while leaving the front on the ground, and still could not get the fill hole high enough to not have the lube coming back out. Is it possible to fill thru the vent tube? That's what I thing I'm gonna try.