Wounded_Fighter Posted October 22, 2018 Share Posted October 22, 2018 So I finished my axle swap (for now, need it to get to work) discovered the new axle sits 1-2 inches forward from old solid 2wd axle and the bump stops rub/pop on the coil springs when cornering and hitting bumps.......?? Other then removing the bump stops, thoughts on what I can do? Link to comment Share on other sites More sharing options...
Jeep Driver Posted October 22, 2018 Share Posted October 22, 2018 Why is it up to 2" forward? and it sounds like the pinion angle is wrong. Adjustable upper and lower arms? Link to comment Share on other sites More sharing options...
Wounded_Fighter Posted October 22, 2018 Author Share Posted October 22, 2018 2 hours ago, Jeep Driver said: Why is it up to 2" forward? and it sounds like the pinion angle is wrong. Adjustable upper and lower arms? 1-2" Is just an eyeball measurement. I don't have adjustable UCA/LCA's. I'll look into some. any other ideas? Link to comment Share on other sites More sharing options...
Eagle Posted October 22, 2018 Share Posted October 22, 2018 What did you use for control arms? Stock height or lifted? Link to comment Share on other sites More sharing options...
Wounded_Fighter Posted October 22, 2018 Author Share Posted October 22, 2018 4 minutes ago, Eagle said: What did you use for control arms? Stock height or lifted? Tried the ones that were prev installed on the jeep, and the ones that came with the new axle. both seemed to push it forward. I can only assume that it is stock height. I have not installed any lift as of currently. Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 22, 2018 Share Posted October 22, 2018 Measure the eye-to-eye length of the LCAs and UCAs. Stock lengths are 15.75" and 15.00" respectively. Link to comment Share on other sites More sharing options...
Eagle Posted October 22, 2018 Share Posted October 22, 2018 4 hours ago, Wounded_Fighter said: Tried the ones that were prev installed on the jeep, and the ones that came with the new axle. both seemed to push it forward. I can only assume that it is stock height. I have not installed any lift as of currently. I don't see any way the original control arms could push a different XJ/MJ/TJ axle 1 to 2 inches farther forward than the old axle. Something is very wrong. How many shims are in the lower control arm frame pockets? Link to comment Share on other sites More sharing options...
Wounded_Fighter Posted November 12, 2018 Author Share Posted November 12, 2018 On 10/22/2018 at 5:59 AM, Jeep Driver said: Why is it up to 2" forward? and it sounds like the pinion angle is wrong. Adjustable upper and lower arms? Pinion/caster angle was wrong. You win. I couldn't put the upper arms in because the bushings were shot. Had to press them out and press new ones. Problem solved. Seems like it's still about 1/2 to 1 in forward to me anyway.. LCAs are 15.25 center eye to eye aftermarket, unknown brand non-adjusable. UCAs are stock Link to comment Share on other sites More sharing options...
Wounded_Fighter Posted November 12, 2018 Author Share Posted November 12, 2018 Strange thing DW is. so before with the new front end I didnt put the UCA's in, I did not have dw at any speed pre or post hitting bumps/ruts etc. UCA's are back on, with new busings on the axle. I can cruise down the road at any speed with no problem, but once i hit a decent bump, HOLY HELL.... hit the brakes and get it under 30mph. first question, Caster angle. What is it suppose to be at if its "Correct" Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 12, 2018 Share Posted November 12, 2018 4 minutes ago, Wounded_Fighter said: first question, Caster angle. What is it suppose to be at if its "Correct" Link to comment Share on other sites More sharing options...
Eagle Posted November 12, 2018 Share Posted November 12, 2018 1 hour ago, Wounded_Fighter said: Strange thing DW is. so before with the new front end I didnt put the UCA's in, I did not have dw at any speed pre or post hitting bumps/ruts etc. UCA's are back on, with new busings on the axle. I can cruise down the road at any speed with no problem, but once i hit a decent bump, HOLY HELL.... hit the brakes and get it under 30mph. first question, Caster angle. What is it suppose to be at if its "Correct" Caster angle is 7 to 8 degrees, with 7-1/2 preferred. Your new LCS are 1/2-inch shorter than factory, assuming Hornbrod's numbers are correct. If you didn't change the UCAs and you shortened the LCAs by a half inch, that reduced the caster angle. Adequate caster is important in resisting death wobble. Caster is increased by adding shims to the LCA pockets on the frame, but a half inch is a lot. You might need to get another set of lower control arms. I'm surprised that anyone would be selling control arms that don't match the factory dimension pretty well. Where did you get yours? [Edit to add] If you are using stock UCAs and shorter LCAs, there is simply no way your "new" axle can be sitting farther forward than your original axle, unless one of the axles had been modified to not sit in the correct location. Link to comment Share on other sites More sharing options...
Wounded_Fighter Posted November 12, 2018 Author Share Posted November 12, 2018 @Eagle They came with the axle when i picked up it. was prev installed on 97 cherokee. I still have the factory ones, it seems like the set from factory is 15" and the "newer" ones are 15.5" roughly center eye to center eye. my LCA's when i pulled them off didnt have any shimming at all in it? I don't understand how shimming the LCA on frame side effects the caster angle though? "edit" I get that, might just be a case of *Looks can be deceiving*) ill throw a pic later Link to comment Share on other sites More sharing options...
Eagle Posted November 13, 2018 Share Posted November 13, 2018 7 hours ago, Wounded_Fighter said: I don't understand how shimming the LCA on frame side effects the caster angle though? The front axle setup is a parallelogram, with four hinge points -- two on the axle, and two on the frame. The upper and lower control arms are the horizontal legs. The two vertical legs, on the frame and on the axle respectively, are fixed. Those dimensions won't change. If you don't change the upper control arm, it won't change (:duh:). So what happens if you replace the lower control arm with a shorter one? The only way it can go in is if you pull the lower hinge point on the axle closer to the frame. This rotates the entire axle assembly around the forward UCA mounting point. If the new LCA is shorter, the direction of axle rotation reduces caster. If the new LCA is longer, it increases caster angle. That's how the factory addresses caster, but they do it from the aft end of the LCA by the use of shims in the LCA mounting pocket. Link to comment Share on other sites More sharing options...
Wounded_Fighter Posted November 13, 2018 Author Share Posted November 13, 2018 @Eagle I got how the length changes it. Just not understanding how a shim between the frame and LCA on left or right side of either LCA driver or passenger side would effect it. Only thing I see the shim doing is making a tighter fitment. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 13, 2018 Share Posted November 13, 2018 The LCA rear mounting holes ares slotted. When you add shims, it increases the length of the arms and increases the caster angle. The opposite when you remove shims. Thus you can adjust the caster angle angle with shims higher or lower, and also equalize the angle on both sides. Link to comment Share on other sites More sharing options...
Eagle Posted November 13, 2018 Share Posted November 13, 2018 To elaborate on Hornbrod's answer: The openings in the frame pockets for the LCAs are slotted. The actual locating of the LCAs is accomplished by an insert called a "clevis," which has round holes and which has two studs coming off the back to anchor it in the frame pocket. When you adjust caster, you're not actually adjusting the LCA, you're shimming the clevis, which moves the LCA mounting hole forward or aft. [Part #5 in the diagram below.] Link to comment Share on other sites More sharing options...
MJCARENA Posted November 13, 2018 Share Posted November 13, 2018 The shims do not go on the sides of the control arm. They go behind the lower control arm at the frame end, to push the control arm forward. Item #10 in Eagles' diagram. Did you really drive it with out the upper control arms mounted, or did I read it wrong? Link to comment Share on other sites More sharing options...
Wounded_Fighter Posted November 13, 2018 Author Share Posted November 13, 2018 11 hours ago, MJCARENA said: Did you really drive it with out the upper control arms mounted, or did I read it wrong? Unfortunately for my stupidity you read that correct. I drove it for 2 weeks without them mounted. 600-800 Miles and upto 85MPH on I-95 Link to comment Share on other sites More sharing options...
Wounded_Fighter Posted November 13, 2018 Author Share Posted November 13, 2018 11 hours ago, Eagle said: That makes SOOO much more sense! I am apparently on a good month of turn the brain off. Link to comment Share on other sites More sharing options...
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