fl_799

I've been building up my suspenson in stages. I recently installed an adjustable Spohn UCA (other suspension mods in signature) and set the pinion angle to 1.7 degrees.

During a hard 1 to 2 shift at WOT I get a **sharp** bang from the rear end. Sounds kinda like a universal letting loose! The Spohn uses a heim joint on the chassis bracket and I'm using the factory hydra bushing on the rear axle.

I did read somewhere (if I remember right) that this can happen from the UCA slapping the underside of the car during heavy shock and stress. Can anybody conform this is the case? Is there is fix for this? As much as I'd dred to do this job again, I'd rather put the stock UCA back on then deal with this when I feel the need to get on it.

James

CrazyAl

I've never heard of a really loud bang or slapping sound. However, it is not uncommon to have clunking during shifting caused by the pinion angle being incorrect. You might try a different pinion angle.

Another possibility is a loose bolt in the rear suspension.

fl_799

Al,

Are you suggesting that the rear pinion angle may be too shallow? I will certainly double check this later today when I'm installing my new H-pipe and just might pull it back to 2-1.5 degrees.

I also installed the Spohn rear swaybar right after the UCA but could make such a loud bang at the top of the 1-2 upshift? I torqued everything on the rear swaybar right to spec on that install and it is very solid.

I do notice that the Steeda UCA has a shock pad instgrated into the design that is supposed to help with deflection onto the chassis which the Spohn does not. Like I said, I only read about this same issue in one post on another forum where he thought he popped a rear universal during the 1-2 upshift at the strip but it turned out being UCA to chassis slap. I think he was also running the Spohn adjustable UCA. I'll have to dig that up to double check.

James

CrazyAl

James,

Keep in mind that I have not personally worked with a Spohn adjustable UCA, nor have I heard of a problem with the UCA slapping the underside of the car. However, based on what you've said, this may be a very real possibility.

I was commenting on the pinion angle becasue I have experienced "clunking" due to incorrect pinion angle. When I first put LCAs on my car back when I had the OEM driveshaft, I set the angle to 2.5 degrees per the BMR literature. I had clunking during 1-2 and 2-3 shifts, especially at lower speeds. I changed my pinion angle to about 1.5 degrees and the problem instantly vanished.

Now then, the clunking that I had was nowhere near as loud as something that could be mistaken for a U-joint failure. Then again, my car is thoroughly sound-deadened, so perhaps it would have been that loud normally, but that was quieting it down?

I'd look under your car and see what there is to see. If the UCA is hitting the body, you should be able to see marks where the contact was happening.

fl_799

Thanks AL,

Yeah, I was able to totally eliminate the clunking with the pinion adjustment. This sound is like somebody hit the underside of the car with a 20 oz hammer during right during the shift. Thanks for the help Al, you know your stuff and are a big help.

Edit: I also read this could be caused from too much weight transfer causing the axle to hit the exhaust or another piece under the car. I'll look for the telltail signs. My Tokico's are a bit on the soft side (5 turns out) in the rear and there is not much play anywhere in the rear suspension. My theroy is that the axle is going have more movement since there is no real areas in the bushings or stamped pieces to take up some of the shock and something is hitting back there under harsh load. I Might turn that magic **** on the Tokico's clockwise to firm up the rear end a bit and see if that helps. Might just work. But otherwise, EVERYTHING under the car is double torqued and solid as hell. Hope this works.

Still have not heard back from Spohn tech support but I'll update on the progress of this issue. Should work itself out with some common sense.

James

The Ghost

I do not see in your sig that you have LCA drop brackets and I see you are lowered. I had a heart stopping POP or BANG whatever you want to call it twice within about a three week period after installing my LCA's and adjustable UCA. I found no reason for this POP. However after installing the LCA brackets i have never heard it again. I set the LCA's to be as flat as possible. Prior to the brackets they were at a pretty steep angle. The UCA is at an even greater angle. I think the combination of the two creates A LOT of twist and lets the UCA make contact. And I can say without a doubt that you will stick a launch much better with the brackets, I don't know all the geometry but the things work.

fl_799

Thank's for the feedback guys. Been under the car all night long after I got home from work today. Put in the Breenspeed H pipe, CDC sequental tail lights and got around to finally instaling the Spohn front sway bar.

While I was under the car, I took a look some extra time to fully position the entire exhaust system from stem to stern, retorqued the panhard bar, the spohn rear swaybar, LCA's and UCA, UCA bracket and turned the rear Tokico's out to 4 turns from 5. I made several hard runs and could not repeat the heartstopping bang fron the rear end although it would probably be a bit less pronounced with the new H pipe in place! Unfortunatly, I could not say what actually fixed (knock on wood) the problem but I will invest in those relocation brackets to finish this project off and do it right.

Thanks again guys, this forum is a valuable resource for me.