Just had a TF long arm upgrade installed and although the shop (400 miles away) did a great install, while looking it all over I discovered the installer had to lengthen the lower rear arms to adjust the pinion angle. The uppers are shortened all the way, but pinion angle is too high by about 2-3 degrees. I want to shorten the lowers to TF's spec because at the installers setting I've got some interference issues and the bump stops are going to be off center. If I do so the uppers will be WAY too long, so I either have to have TF send me some shorter ones (not sure they exist) OR, cut about 1/2 off the lowers at the flex joint. Anyone tried to cut the arms? Any issues?

Using something like a horizontal bandsaw would be the best bet, cutting it with an abrasive cutoff wheel may make getting the new threads started again a little interesting.

Jerry
Can they just be milled down to keep it more precise? If that will work let me know and I will have my guys do it in our machine shop.

I know the short arms they offer two lengths. I'd give TF a call first before cutting anything.

you mean you want to shorten the shank of the joint or shorten the arms? I am assuming the joints....actually I am not sure what you are asking

Ive done this many times. Goody is spot on use a bandsaw. If you have a tap u can get away with using a cut off wheel. But safest way is a bandsaw. You will need to trim the arm along with the shank to shorten. Make sure you have enough threads on the shank before you cut.

How many threads or thread length would/should be engaged or required after cutting.

If it's a 7/8-18 threaded joint (TeraFlex size).

.

Thanks all. What I need to do is drop the pinion nose about 3 - 4 degrees. Right now there's 9 degrees on the driveshaft and 14 degrees on the pinion and I'm geting some driveline rumble under certain situations. This rig likes the pinion about 2 degrees low. The installer has the uppers run all the way in, and ran the lowers out about 1/2" longer than TF's specs, which is causing some binding, slight spring bow and the bump stops aren't aligning as I'd like em. But, biggest issue is the pinion angle.

I want to shorten the lowers back to TF spec, then adj pinion angle with the uppers, but I'm guessing the upper arms will have to be shortened about 1/4" - 1/2" to pull it off. The easiest deal would be if TF has shorter rear uppers available that I can swap out, but if necessary I could just have 'em shortened. (BTW, thanks Steve, I may take you up on the offer!) I can see that the installer started to shorten one of the uppers with a cut off wheel but stopped and just lengthened the lowers as much as he dared. Issues with shortening the arms I can see right off the bat are getting the cut off square, and worse, hosing the threads so the joint won't go back in. Also figuring the joint shank may have to be shortened. One could "F" this up pretty easily.

Interesting that I had the same issue on this JK with the TF short arm kit I originally installed. I corrected it by doing as this installer did, extending the rears a bit, but it only took about 1/4" lower arm extension. He's got the rear brackets welded in the right places. Beautiful welding job, too.

Update: I determiend the installer had left about two more turns available on the uppers, so I ran them all the way in. Only got me about 1 degree, so I'm at a bit less than 10 degrees on the driveshaft and about 13 on the pinion. (CRAP!) So, only option apears to be shorter upper rear arms. Call to Joe at Teraflex tomorrow to see what they have. If nada, then it's the bandsaw or mill. Moab's coming up, usual fire drill.

Could you show us pics of the interference issues that are happening when the rear lower arms are lengthened enough to get a 1-2 degree pinion down from driveshaft difference?


Sent from my iPad using Tapatalk HD

As the installer had it set up the rear sway bar links were binding against the control arm brackets, the springs were bowed and the bump stops weren't going to line up on stuff. Shortening the uppers got the bind out of the links and reduced the bow (I have the perches corected with wedges). If I extend the lowers a bit more it will help the angle but then it may have tire rub at the back of the wheelhouse, whch is already trimmed. Gonna have to work it a bit more. We'll see what Teraflex Joe has to say tomorrow.

Update: To get the pinion angle 1 degree under the driveshaft without cutting the uppers required running the uppers all the way in, and extending the lowers about 1/2". Looks like it will work this way. But I need to ramp it or get it on my favorite test rocks to be sure.

Adding an observation. Got some quick measurements of the control arm lengths yesterday and compared them to Teraflex's recommended settings.

Front upper control arms: TF Sec = 27 3/4 inches, Installer = 27 3/4
Driver side front lower control arm: TF Spec = 33 9/16 inches, Installer = 33 9/16
Passenger side front lower control arm: TF Spec = 33 11/16 inches, Installer = 33 9/16

Rear upper control arms: TF Spec 19 1/2 inches, My setting = 19 3/4" (fully adjusted in)
Rear lower control arms: TF Spec 35 1/8 inches, My final setting = Driver side 35 13/16", passenger side = 36 1/16". (1/4" thrust stagger retained per original installer's setting.)

Because of all the variability that can stack up between the brackets, mounting locations chosen by the installer, etc., you can't really rely on a set of specs. However, pretty clear the rear upper arms are longer than anticipated, making extending the lowers essential to get the driveline angle nailed. I need to get it on some ramps or rocks & stuff the rears to see if I have any wheelhouse rub. If so I'll be forced to cut the uppers back at least 1/2" & pull the lowers back in. I may get it on an alignment rack as well to check that thrust angle because it's reversed from how I set the short arm. Otherwise it all looks good.