Getting the pinion angle right

[TurboTJ]

I have a 2006 TJR with a 2.5 inch OME/Currie lift and a Barnes skidplate that raises the TC about 1 inch. I do not have a MML. I put a Tom Woods double Cardan driveshaft in and I am having trouble getting the pinion angle just right. Right now it is about 3 degrees lower than the shaft. The lower control arms are shortened almost as much as they can be (within two threads of minimum length). Any shorter than that and the slip joint in the shaft stacks under some conditions of articulation. The upper control arms are as long as they can be before the trackbar hits the frame crossmember (the trackbar is a JKS with the angled bracket). There doesn’t seem to be any way to further increase the pinion angle (I need another 2 degrees up) other than by cutting away the frame crossmember or by putting in much larger bump stop extensions. I already have 1.5 inch extensions which is twice the standard OME size. Has anyone else run into this problem? Is there a solution? Even though my pinion is 2 degrees too low I have zero vibes but I would like to get the angles just perfect.

 

[jjvw]

How did you determine the length of the new drive shaft before these pinion adjustments?

What specifically are the bumps extended for? If it is the shocks, be aware that the lower shock mounts move lower as the pinion rotates up. I mention that simply to add to the complexity of the moving parts.

You may need to trim the gas tank mount for the track bar. A MML will certainly help.

I recall Savvy lower arms being able to adjust shorter than stock. But then your current drive shaft becomes a problem as you mentioned.

 

[TurboTJ]

How did you determine the length of the new drive shaft before these pinion adjustments?

What specifically are the bumps extended for? If it is the shocks, be aware that the lower shock mounts move lower as the pinion rotates up. I mention that simply to add to the complexity of the moving parts.

You may need to trim the gas tank mount for the track bar. A MML will certainly help.

I recall Savvy lower arms being able to adjust shorter than stock. But then your current drive shaft becomes a problem as you mentioned.

The 1.5 inch bump stop extensions are to prevent the track bar relocation bracket from hitting the tub. The OME supplied 20 mm extensions are inadequate for this and I've got a dent in my tub to prove it. I now have the angled JKS bracket but the same is true with that one.

I did not measure for the drive shaft. I just bought the Tom Woods part that was specifically designed for the TJR. Even if the driveshaft were shorter I would not be able to shorten the lower Currie arms more than the remaining two turns on the JJs. My axle is already somewhat forward of where it should be anyhow.

 

[jjvw]

I'm surprised the guy at Tom Wood didn't ask for a measurement.

 

[TurboTJ]

JKS recommends not using their angled track bar relocation bracket if the lift is less than 3 inches. That should prevent the track bar from hitting the frame crossmember. I am debating whether to do this or not. It will mean a pretty considerable angle between the track bar mount on the frame and the one on the axle although I guess the JJ can absorb that. And of course the non-optimal location of the track bar will result in more side-to-side axle movement. What do you think, good idea or not?

 

[BuildBreakRepeat]

Although you already got the drive shaft, it’s bad practice to not measure the shaft length needed after lining up control arms and fine tuning pinion angle. There is no one size fits all drive shaft - sorry to hear they might have sent you the wrong length

 

[TurboTJ]

Although you already got the drive shaft, it’s bad practice to not measure the shaft length needed after lining up control arms and fine tuning pinion angle. There is no one size fits all drive shaft - sorry to hear they might have sent you the wrong length

I am not sure it is the wrong length. As I mentioned before the lower CAs are adjusted almost as short as they can be (2 threads remaining, which brings the axle forward of where it really should be and runs the driveshaft slip joint up against the stop) but I can't lengthen the the upper CAs enough to get the proper pinion angle without the trackbar hitting the crossmember at full stuff. Removing the trackbar relocation bracket will solve that problem because it will lower the axle end of the trackbar about 2 inches, but I am not sure that is really the optimum solution because of other problems it might create.

 

[dbbd1]

JKS recommends not using their angled track bar relocation bracket if the lift is less than 3 inches. That should prevent the track bar from hitting the frame crossmember. I am debating whether to do this or not. It will mean a pretty considerable angle between the track bar mount on the frame and the one on the axle although I guess the JJ can absorb that. And of course the non-optimal location of the track bar will result in more side-to-side axle movement. What do you think, good idea or not?

I did.

 

[TurboTJ]

I did.

To be clear, you did remove the track bar bracket? And you've had no problems?

Thanks,
Jim

 

[dbbd1]

To be clear, you did remove the track bar bracket? And you've had no problems?

Thanks,
Jim

No. I used their angled bracket on my 2.5" lift.

 

[bobthetj03]

If you have no vibes roll with it. Your other option would be to run a MML. That will change the relationship of the ds angle to pinion angle, which will get you your adjustment. Dropping the skid would be another option, but then you are defeating it's purpose. I have the same skid and MC adjustable arms and have all kinds of adjustment left either direction, so it's strange your arms don't. I am bumpstopped for the angled bracket and 33's as well. My track bar just kisses the tank skid at full droop.

 

[Alex01]

I think a mml would help. But like @bobthetj03 said if you don't have any vibs it may be best to let it be.

 

[TurboTJ]

If you have no vibes roll with it. Your other option would be to run a MML. That will change the relationship of the ds angle to pinion angle, which will get you your adjustment. Dropping the skid would be another option, but then you are defeating it's purpose. I have the same skid and MC adjustable arms and have all kinds of adjustment left either direction, so it's strange your arms don't. I am bumpstopped for the angled bracket and 33's as well. My track bar just kisses the tank skid at full droop.

What size bump stop extensions did you use?

 

[Jerry Bransford]

I'm surprised the guy at Tom Wood didn't ask for a measurement.

I'm not, they have done so many over the years that they have developed guides on what various model combinations require once you tell them the lift height. Tom Wood & I talked about that years ago.

 

[bobthetj03]

What size bump stop extensions did you use?

I was using 1.75" bumps, but I added a 0.5" BL, so I'm now at 1.50" bumps. Can't go any less due to tire size.

 

[Alex01]

I was using 1.75" bumps, but I added a 0.5" BL, so I'm now at 1.50" bumps. Can't go any less due to Wallet size.

Fixed it for you

 

[jjvw]

I'm not, they have done so many over the years that they have developed guides on what various model combinations require once you tell them the lift height. Tom Wood & I talked about that years ago.

Their first or second question to me was if I measured for the length. The more I described the Jeep the more things changed from the initial recommendation.

 

[fljeeper]

Why not use an adjustable track bar and get rid of the aftermarket track bar bracket?

 

[TurboTJ]

Well, it is adjustable, but my understanding is that you want the track bar to be as close to horizontal between the pivots at normal ride height. That will minimize any side-to-side movement of the axle.

 

[astjp2]

Well, it is adjustable, but my understanding is that you want the track bar to be as close to horizontal between the pivots at normal ride height. That will minimize any side-to-side movement of the axle.

At your lift, its a non-issue. I am running a 4-5" lift on my LJ, adjustable track bar and no relocation bracket. Rides fine and does not have that rear sway that my wife's old TJ had with no lift. Just get the axle centered. Tim