Loud bang on launch

[teeje]

Since I've been starting threads on tedious things that dont matter, I figured I'd start a thread on something that definitely seems important.
I'm going to start with what's new
Ford performance one piece drive shaft
Sway bear bushings and end link bushings (poly)
Bmr lower and upper rear control arms stock upper bracket with new stock style axle housing bushing (where can I get a poly one??)
Sr performance lowering springs

Before I upgraded to the one piece I noticed I'd get this loud ass bang in the rear of the car on launch with 2 step at 3000 rpms and higher. After I went to the one piece figuring that was the culprit and to get that heavy ass 2 piece out I noticed the the bang is gone when shifting aggressively but no on launch. I've searched everywhere but I'm still coming short on finding the issue. My assumptions are my DS is hitting the tunnel, my right rear shock is screwed (which both are new) I'm hitting the bump stops (shaved the top part off after lowering) or my diff or one of my axles is letting go. I have 355s right now and I'm probably going to go 373s but I'm almost positive the diff or axles isn't the issue. It literally sounds like someone is under there with a big sledge hammer and hitting the underside of the car and I have no clue where it's coming from. I'm almost wondering if it's the pinion angle which, honestly looks straight or I need to get lca relocating brackets. Since I suck at words and cant figure out the end to my post ... have at it?


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[sman247]

Try checking the bushing to the rear upper control arm, I had the same issue and it turned out the bushing had broken off so the bolt was just clunking around

 

[teeje]

Try checking the bushing to the rear upper control arm, I had the same issue and it turned out the bushing had broken off so the bolt was just clunking around

To which part? The mount or the diff? Bushings on the arm are new

 

[RocketcarX]

The stock upper control arm mount will make some noise under heavy loads. A loud bang more likely means something is loose.

 

[teeje]

The stock upper control arm mount will make some noise under heavy loads. A loud bang more likely means something is loose.

I gave all those bolts an extra uggadugga after torquing to spec

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[46addict]

If your UCA is adjustable you should be able to get the pinion angle where it needs to be without getting LCA relocation brackets. Do you know what your angle is now?

As for the banging noise, I'm just guessing here but if there is enough movement of the body/axle, you could be hitting the exhaust on the axle. The pipes that go over the axle tend to bottom out on lowered cars and this area will flatten if hit enough times.

 

[teeje]

I dont have an adjustable uca what shoudk the angle be?

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[46addict]

That depends on who you ask. But I would start with -1.5 and go from there once you get some adjustability.

 

[teeje]

Alright. I'll have to figure out a smart way to measure this. Rear suspension has to be under load correct

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[bl817]

Prothane sells a poly bushing for the axle mount. you use the metal sleeve tho so you need to gut the rubber out. LCA relocating brackets don't necessarily effect pinion angle as so much launch angle. your rear LCA need to be parallel to the ground or rear mount slightly lower than front. I'm using SR springs as well and had to use relo brackets to get the launch angle right. you can measure your pinion angle with your car on ramps. use a magnetic angle finder (5$ at HF), measure pinon flange then driveshaft, difference between numbers is pinion angle. I'm sure you know but 05-09 UCA arm and mount are different from 11-14 and are not interchangeable. you can use 11-14 mount AND UCA on 05-09 cars but not 05-09 UCA and 11-14 UCA mount and vice versa. good luck

 

[stkjock]

you lowered the car and don't have an adj lower or upper control arm?

you have to adjust the pinon to -1.5 to -2.0*

http://www.s197forum.com/threads/if-you-adjusted-your-pinion-angle-come-in.8330/

 

[46addict]

Alright. I'll have to figure out a smart way to measure this. Rear suspension has to be under load correct

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Yes

 

[redfirepearlgt]

I'd be surprised if its pinion angle related. BMR as I recall claims -2 for poly and -1 for solid bushings. And yes that is loaded. -2 degrees is the number you are shooting for. Page two of this BMR installation manual (you should have received one with your kit) explains the process.

https://www.bmrsuspension.com/siteart/install/UTCA032.pdf

Out of curiosity did you remove the stock upper control arm mount for any reason? The torque on that front bolt is absurdly high. It is to be tightened to 200 ft/lb. BTW that is a one time use bolt as well. If it is not torqued to the correct number if it was removed for whatever reason, your popping noise is likely coming from that. Common thing to happen when doing a full UCA and upper bracket replacement. The two lower bolts are torqued to the normal 85 ft/lb. Good luck.

Pull the rear seat out and have someone you trust sit back there and listen when you make a hit. May help isolate things.

 

[teeje]

I'd be surprised if its pinion angle related. BMR as I recall claims -2 for poly and -1 for solid bushings. And yes that is loaded. -2 degrees is the number you are shooting for. Page two of this BMR installation manual (you should have received one with your kit) explains the process.

https://www.bmrsuspension.com/siteart/install/UTCA032.pdf

Out of curiosity did you remove the stock upper control arm mount for any reason? The torque on that front bolt is absurdly high. It is to be tightened to 200 ft/lb. BTW that is a one time use bolt as well. If it is not torqued to the correct number if it was removed for whatever reason, your popping noise is likely coming from that. Common thing to happen when doing a full UCA and upper bracket replacement. The two lower bolts are torqued to the normal 85 ft/lb. Good luck.

Pull the rear seat out and have someone you trust sit back there and listen when you make a hit. May help isolate things.

The one under the seat Is one time use? Or the one that goes to the UCA through the bracket?

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[redfirepearlgt]

The one under the seat Is one time use? Or the one that goes to the UCA through the bracket?

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Read the install manual I provided. As it states that is a one time use bolt. That is why they send a new one with the Upper relocation bracket. 200 ft/lb is a ton of torque. So if you removed that upper bracket for whatever reason, you may wish to replace the bolt as well as verify that the torque is properly set.And don't forget to check the lower bolts that go up through the bottom to ensure they are torqued to 85 ft/lb. Again this is all assuming for whatever reason you removed the stock bracket to install the aftermarket UCA.

The LCA bolts are only torqued to 129 ft/lb but they as well are considered to be a one time use. People reuse them as I have. But when it comes to torque levels at 200 ft/lb where it is specified one time use I become much more compliant. It's not a TTY application bolt (which should never ever be reused) but the level of torque being placed upon it when it is tightened is a mass amount.

 

[teeje]

Gotcha. Will do. And yeah I took the bracket off. I want going to fiddle with a wrench for the UCA

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[07 Boss]

The hole the upper arm uses for the bolt on the chassis mount is larger than the bolt.
When you use and aftermarket arm with the sock mount it will clunk no matter how tight you torque it down. You can either get a new mount or I think Steeda makes some stepped washers or something to prevent the bolt from shifting in the hole.

 

[teeje]

It did it with the stock style too because I replaced the mount and uca with a stock one before going with bmr. The UCA itself is tight but the bracket might be loose

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[Heaten m90]

So yeah, umm, there’s like these rubber yellow cake looking things that sit on the axel tubes.....Did you remove them? I did for weight reduction purposes and mine would randomly clunk sometimes too. I chalked it up to those things

Also the first time I blew up my 8.8 (yellow cakes were still installed at this time) it would randomly make extremely loud clunking noises come to find out, it was eating Pinion ring gear bolts That were left loose. The last bolt ended up shearing itself when I was racing a hellcat on highway. Crazy part was all I did was replace the bolts and the thing was back on the road. I shit you negative

 

[teeje]

Nope bump stops are still there and lol that's great

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