Rear LCA's/Rear End Gear Problem (Opinions)

[marvinmycat]

I'm pretty sure I know what the problem is, but wanted some informed opinons first...

A few months back, I had a posi and 4.10 gears installed on my 98 auto. When the shop went to install them, I was informed that one of the axle bearings had spun, but the mechanic was 99% positive that he could fix the bearing and make it usable again. This shop does nothing but rear ends, so I trusted the guy. For two months I have been driving on the setup, and haven’t heard a single sound from the pumpkin back there.

Two days ago, I had my rear adjustable lower control arms put in by a professional mechanic. These are the Granatelli ones with the weight jacking system. They are also adjustable length-wise to accommodate moving the axle backward and forward. As such, this required that we measure the length of the old stocker LCA’s and adjust the length of the new ones to match.

Before the installation, the car would pull slightly to the right, but there is no tread wear going on up front at all. After the installation, the car seems to pull just a little more to the right, but almost to the point of not being any more detectable than before. Now that I have my rear seat out for the installation of functional side scoops, I can hear a noticeable whirring noise coming from the rear end, where like I said before, was quiet as a mouse.

Knowing that the car feels like it pulls a little more to the right, and now the new noise coming from the rear, do any of you think that the length on the right LCA should be lengthened just a bit?

Would a shorter LCA cause the driveshaft to be a fraction too long and compressed into the rear posi that this would cause some excess pressure on the unit, thereby resulting in the new noise?

I’m assuming that lengthening the right LCA would correct the extra pulling to the right as well, correct?

Associated with all the above concerns, I'm thinking that if the new LCA's werent' set exactly to the corresponding old LCA's, that the rear axle is now under a little stress being that it isn't perfectly straight. I didn't bother to take note of the where the axle connects to the pumpkin housing, so I'm thinking that the new angle that the axle connects to the rear might be the cause for the noise. Yes, no?

Any thoughts or suggestions are appreciated!

Update:

OK, I just got the right side LCA lengthened one full turn, and the car now tracks exactly as before. However, that whirring noise is still there. The tire pressure is the same or correct, if you will. I'm wondering if I lost some gear oil in the pumpkin, but when I look at the entire assembly and axles, I see no indication of leakage anywhere.

Any suggestions other than take it in to be looked at, which is what it looks like I'm going to have to do?

Thanks!

 

[GT2000JAY]

First, and foremost, have the alignment checked 80-90% of alignment problems are up front - even if the rear end is causing a push the front tires will still wear in an irregular fashion from having to correct the push (ie. turning the wheel slightly to compensate). Feel the inside and outside shoulders of the front tires - run your hand front to back and then reverse - if one way feels smooth and the other is rough, that's called feather wear.

As far as the whirring noise, I can't help much - did they check the pinion angle when they did the LCA's? Not sure if that would cause noise in the differential, but it's somewhere to start.

Jay

 

[marvinmycat]

I'm not overly concerned with the front end alignment right now as I usually get an aligment this time of year when I get my summer tires on. I've already checked for the feather wearing, and there isn't anything of note going on there.

Stupid question, what is the pinion angle you speak of?

 

[GT2000JAY]

The angle the drive shaft meets the rear end - when you make major suspension changes (lowering springs, lca's, etc.) you change the angle the driveshaft meets the differential.

 

[marvinmycat]

OK, thanks! I wasn't too sure what you meant, but yea, that does make sense. I lowered the car before I did the gears and T-Lok. Then I went and put the adjustable LCA's on, and jacked the rear end back up some. I didn't think that the angle of the driveshaft would make this kind of noise or interfere with the operation of the gears and T-Lok. I was under the impression that there is a universal joint back there.

I'll have to take it and see what the mechanic can find out for me. I'm really hoping I don't have to go through installing another T-Lok, install kit, plus labor! This would have made getting an 8.8 rear end in the first place justifiable!

Thanks for the info and advice!

 

[GT2000JAY]

There is a u-joint back there, but from my experience doing my own LCA's and springs there is still a spec pinion angle. Good luck getting it sorted out - sorry I couldn't be of more help.

Jay

 

[marvinmycat]

OK, after being up 24 hours, I took the car into the shop that put the LCA's on after work. Mind you that this job was done on the side and off the books, thereby saving me a butt load of $$$.

Anyway, it turns out that when we reused the rear brake cable brackets that were on the stocker LCA's, we had to bend them a little so they would fit into the pre-drilled holes on the new LCA's where your sway bar would go (a future mod!). The cables were a little tight and when I got the car back home, I bent them up higher to get some more slack in the brake cables.

This didn't do anything for the noise I was hearing. The noise, to be more specific, sounded to me like the noise you would hear on earlier ricer models of synchromesh running on low gear oil. Or it could be described as two pieces of metal being rubbed together in a circular motion. I was convinced that it sounded like the gears, but it turns out that both the brake cables were tight and weren't releasing the brake pads from the rotors all the way. Also, with the back seat out, the sound would seem to come directly from in between the two front seats, making it appear to come from the pumpkin under the car.

We took the brakes apart, cleaned them up, re-greased the calipers, and cut one of the brackets off the LCA's. The guy couldn't get the nut off as I used my super human strength to put them on, so I told him I'd take them off and fabricate something up to replace them and not waste anymore of his time.

Went for a drive and the sounds weren't quite as loud, being that only one bracket had been cut off, but the louder than hell brake groaning when I applied the brakes was gone.

The chirping I heard was due to the brake cables being tight and not releasing the pads enough, thereby causing the tire to skip when I was in my company's parking lot which uses a finer pavement than the crap the streets are made out of, making it easier for the tires to chirp when I made sharp turns. The mechanic also checked the pinion angle and he said that it wasn’t changed enough to cause any problems either.

So, after three hours of in the shop, my constantly asking questions, he identified the problem, and now I've got a little work to do. Also, I will now be able to change my own calipers and rotors in the future! The cost? Free!!! These guys rock!!!!

If you put gears in and you think that they may be going, I was told that you would not mistake them for anything else as it sounds like a school bus grinding to a halt (FYI).

Thanks for all your helps guys, just thought I'd at least share some of the information I got this morning with all of you in case someone else needs it!

BTW, these LCA's rock! There is no more wheel hop or the car's back end losing traction over the bumps when traveling at high speeds on NY's lousy highways! Get some, what a difference!!!