Rear end "popping" noise, need help and opinions

[rjsmith1973]

Do your trailing arms have a port to inject some grease into the bushing? I have the spohn trailing arms and they were making almost the same popping/creaking noise you describe. One grease gun later and things are quiet as can be.

[Fiftydriver]

Yes my trailing arms do have grease zerks but they are impossible to lube with a straight grease gun head so I have ordered a 90 degree grease head. I am hoping that maybe this is the problem. If it is, will be a cheap fix!!!

[tadams72]

I'm with a couple other folks here. Popping with slipping tires tells me your posi is not operating properly. I can honestly say I've never had a limited slip dif do that (act like a spool). I also don't agree that upgraded axles are going to fix it. I would not look at spending a bunch of money to ship it back to Ted just yet. You are close to Great Falls and they are big enough to have a reputable performance shop in town. Once you are comfortable, get some help troubleshooting and if necessary, open it up. Still going to be cheaper than labor and truck shipping it 2500 miles. On top of that, from looking at your sig, you're not in the HP range requiring beefier axles yet. Just out of curiousity, what is the "posi upgrade"?

[Fiftydriver]

Tadams72,

All I know for sure is that the diff is not making the popping noise. Now it may be caused by the posi being overly tight but whatever is popping is happening on the outer ends of the axles. This leaves either the trailing arms or the outer CV joints on the axles.

Will lube the trailing arm bushing and see what that does and go from there.

I am not yet in the relm of high performance with my set up, probably running a bit shy of 400 rwhp at most but I am building the rear end to get ready for some real power here in the next year or two. Plans are for a forged bottom 416 stroker, moderate boost Maggie for a preformance goal in the 650 to 700 rwhp range. Nothing EXTREME but certainly enough to justify the investment in the upgraded axles just for piece of mind.

I have a hard time believing that these 1400 hp rated axles would not be built with much better CV joint finish and fit which would help with "popping" under load. Maybe I am wrong on that but looking at the difference in finish of the factory and upgraded CV joint parts, it seems there is a DRAMATIC difference in fit and finish quality.

As far as the posi upgrade, from what I understand, the limited slip clutch springs are replaced with much heavier springs to hold more torque without slipping.

To be honest, this rear end is MUCH tighter then I was ever expecting it to be from what I was told about how the new rear end would handle street driving.

I would not mind the wheel slipping much at all because you only feel that if you happen to hit pavement with fine gravel on it or something similiar and then you just give it a bit of throttle and you do not even notice it.

Its the popping and snapping at low speed turns that really gets annoying and that I need to get rid of.

Its hard to know which way to go. You ask all the experts and some will say get new axles and that will solve the problem. Others say it will make no difference with new axles, some say its the trailing arms, others say its the posi unit.

I understand you have to pay to play but I am not overly fond of throwing money blindly to solve a problem. No problem spending money to solve or correct a problem but just throwing money blindly is hard to do. Just looking for a direction to go.

Also, you would be surpised at the lack of quality performance shops in the Great Falls area. Do you know of any good ones in the Billings area? Would be more then willing to take a road trip to get to a good shop that I had confidence in.

Thank,

[Slowhawk]

Sounds like the posi is too tight. The pop is either an axle or the posi unlocking(breaking free).The purpose of a posi is to let the inside wheel spin freely on hard corners.If you preload the clutches to much it will make it feel like a spool.Great for drag racing but not the best for the street,expecially in the rain. Luckilly these cars have fairly big wheel studs so a wheel won't sheer them off.

[flht99b]

It may have already been mentioned but instal the 4 oz bottle of GM's differential friction modifier and go to a parking lot and drive in tight circles and figure 8's in each direction for awhile. Sounds like the posi clutches are sticking and when they release the "pop" noise you hear could come from any number of rear suspension parts but the root cause is the posi plates/clutches sticking. I had the same issue with a stock diff ( no heavy spring in posi ) when I changed the diff fluid. I went with Mobil 1 75w-140 lube without the GM friction modifier and the posi clutches groaned and occasionally popped around low speed corners. Added the GM friction modifier to the diff and did the parking lot circles and figure 8's and all is quiet now.
Ed M.

[Hendrix-Engineering]

It sounds like a tight diff to me and im sure Ted can take care of ya,$1000 for labor is way to much.I have a set of stock axles that i know dont pop i can send you if you want to try that first.If your getting a sc you probaly want axles any way and i can help you with that as well. call anytime.

[Stingr69]

Spools are described as NO differential action. Open differentials are completely free to rotate in either direction. the Limited Slip differential is somewhere in between those 2 extremes as it has a clutch pack friction system in place to make it harder for one axle to rotate at a different speed than the other side. You can leave the pressure on the clutch packs loose and it will be more like an open rear end. If you tighten up the pressure on the clutch pack it will be more like a spool. If the clutch pack is set up very tight, the axles will actually twist and wind up like a spring on turns as the tires are sticky and the clutch pack resists any differential action. If you hear popping it can be the axles releasing the "twist" as they return to straight. The twisted axles will release this force in two possible ways. Either the tires slip or the clutch pack gives in and allows the force to be released by movement inside the differential. Either way, the axles can "snap" back to straight and you can hear the popping sounds. I beleve JRE is suggesting stiffer axles that might not twist as much as the factory axles so that solution "might" help in your situation. Stiffer axles will resist winding up like a spring and that will force the tires or clutch pack to slip before anything can wind up reducing the "snap". Given your current setup, the differential clutch pack is set tighter than you want now.

The way I see it, you can try the (cheap and easy) friction modifier and figure 8's again and if that isn't getting it done then consider sending the posi back and have the clutch packs loostened, or try adding some stiffer axles (that you may need in the future anyway).

Just trying to help here.

-Mark.

[Fiftydriver]

Thanks guys for all the replies. I have done more figure 8s in this car then I care to talk about!!! LOL

Right now I am running two 7 oz bottles of Redline posi additive. I can not imagine that 4 oz of the GM lube would make more difference then 14 oz of the redline product.

I think right now this will be my approach to this problem.

1. Get the trailing arm zerks lubed properly once my 90 Degree head gets here for my grease gun.

2. Get the upgraded axles as I plan to need them down the road anyway and hope this helps to eliminate the popping. If not, I will at least know that its not the trailing arms or the axles causing the problem with the popping.

3. Finally, if all else fails, pull the Diff and send it back to Ted to get it adjusted with lighter springs in the clutches. This may not be recommended until I get the S/C installed and things up to where my goals are performance wise as I may need the stiff posi clutches when I get to my and goal in performance.

Thanks for all the help, if anyone has any more recommendations on having similiar problems and how they solved it I would love to hear about them.

[usmcjlp]

Fifty driver,

I had the same issue as you. PM me your number and I will call you to discuss. Your problem is the Posi upgrade. Pull it and your car will no longer make that noise.

I purchased AAM 3.70s, BMR bushings, JRE's posi upgrade, and billet end caps. Now let me start, by saying that I am not bashing any vendor or product. I am currently at 650+ rwhp and was told that the posimod would help traction. This is my daily driver in the summer. I repeatedly asked whether this would affect daily drivability. I was told it would not. I now know that the wheel chirping is considered normal.

I also had the loud clunking and a sound like a spring releasing whenever I did a tight right turn or a descending turn. I could also feel the rear end fish tail somewhat. In my case, my launches sucked afterward. I would get a horrible shaking and a lot of noise on launch. The rear end felt like it was going to come off.

I too swapped the fluid multiple times and added the posi additive. I did more figure 8's than I care to admit. It did not help at all.

I had a local shop pull the differential and put the clutch assembly back to stock. Problem went away and no further issues since. This mod completely ate up my rear tires. So in the end I paid double the labor and had to replace my rear tires. It is the only mod that I regret making. But, you live and you learn.

Now, I am sure that for the drag racers on here, the chirping is no big deal. I couldn't live with it. I would not recommend it to someone who wants to maintain stock like driving manners.

[tadams72]

Originally Posted by Fiftydriver

Tadams72,

All I know for sure is that the diff is not making the popping noise. Now it may be caused by the posi being overly tight but whatever is popping is happening on the outer ends of the axles. This leaves either the trailing arms or the outer CV joints on the axles.

Will lube the trailing arm bushing and see what that does and go from there.

I am not yet in the relm of high performance with my set up, probably running a bit shy of 400 rwhp at most but I am building the rear end to get ready for some real power here in the next year or two. Plans are for a forged bottom 416 stroker, moderate boost Maggie for a preformance goal in the 650 to 700 rwhp range. Nothing EXTREME but certainly enough to justify the investment in the upgraded axles just for piece of mind.

I have a hard time believing that these 1400 hp rated axles would not be built with much better CV joint finish and fit which would help with "popping" under load. Maybe I am wrong on that but looking at the difference in finish of the factory and upgraded CV joint parts, it seems there is a DRAMATIC difference in fit and finish quality.

As far as the posi upgrade, from what I understand, the limited slip clutch springs are replaced with much heavier springs to hold more torque without slipping.

To be honest, this rear end is MUCH tighter then I was ever expecting it to be from what I was told about how the new rear end would handle street driving.

I would not mind the wheel slipping much at all because you only feel that if you happen to hit pavement with fine gravel on it or something similiar and then you just give it a bit of throttle and you do not even notice it.

Its the popping and snapping at low speed turns that really gets annoying and that I need to get rid of.

Its hard to know which way to go. You ask all the experts and some will say get new axles and that will solve the problem. Others say it will make no difference with new axles, some say its the trailing arms, others say its the posi unit.

I understand you have to pay to play but I am not overly fond of throwing money blindly to solve a problem. No problem spending money to solve or correct a problem but just throwing money blindly is hard to do. Just looking for a direction to go.

Also, you would be surpised at the lack of quality performance shops in the Great Falls area. Do you know of any good ones in the Billings area? Would be more then willing to take a road trip to get to a good shop that I had confidence in.

Thank,

Fiftydriver,

I see you have several good pieces of advice since you wrote this that really probably have you pointed in the right direction (usmcjlp in particular). Can't help you on the Billings shops yet as I am deployed overseas. However, if you are still having problems in two weeks I will be back there and would be happy to ask around for you. I know there are a few other guys on the forum from your neck of the woods. I remember one guy from Big Sandy that has a 650+ hp SS. He either knows a lot or knows a good shop so you might try searching for him (sorry I just don't recall his handle right now). Again, if I can help when I get back, let me know. Good luck.

Travis

[Fiftydriver]

Usmcjlp,

I am thinking along the same lines as you on this. To be honest, before the rear end upgrade, I had no problems at all with one wheel burn outs. I realize I will be pushing alot more HP someday but like you, this is a pleasure car. Much more of a daily driver and will never be a strip car even when "built". I will build it to GO but is seldom will be driven hard enough to have to worry needing a rigid posi unit.

I may look into what the GM techs will charge me to change the upgraded posi unit back to factory.

THanks for your imput and time. Most appreciated.

[Fiftydriver]

Tadams72,

I think I know who your talking about that lives in Big Sandy. Hell I could probably drive over there and find him if I needed to.

I think for the time being I will pull the upgraded posi and convert it back to stock at least until I am pushing the HP that may or may not require the upgraded posi unit for what I do.

In all honesty, I never had any one wheel burn outs with the factory rear end. In hind sight, I think I would have been better off just doing a gear change and leaving it at that. I then would have had enough cash to get a set high HP axles right now!! Oh well, live and learn as has been said.

Thanks for all your time. May have to look you up when you get back or if I am in the Billings area.

[Fiftydriver]

OK, next question.......

I am thinking about going back to the factory posi limited slip system in this upgraded rear end.

My question is if there are any aftermarket limited slip clutch systems that have been offering better holding power but with near factory street drivability out there. I think I remember seeing one upgrade system in one of the car rags but can not find it out there.