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Discussion Starter #1
Yesterday I drove almost 3 hours to a shop to get my gears installed, and no local shops could give me a decent quote (all the local shops wanted between $1000 and $2000 for labor to install new gears..). The shop I went to has a good reputation and the guy has a lot of experience installing gears in the Ford 8.8 rear ends. Let's get to the point:

The guy let me be in the shop and observe his work, and except for a problem removing the old 3.27 pinion everything went smooth. He measured the pinion depth using a special FRPP tool and shimmed appropriately. After all was said and done the backlash was 0.007, he told me it was so close to spec (0.008-0.014) that it would be fine, and that the gears will break in giving the end result of a backlash that is within spec. The guy reused the old crush sleeve, but all other hardware was new. He said it does not matter as long as the preload set on the pinion nut is correct.

On my way home I got on the interstate and felt a vibration throughout the car during deceleration at speeds above 65mph. This only occurs above 65mph, and is worst at part-throttle deceleration. If I let all the way off the gas it still vibrates, but not as bad. I called the guy and we went back to the shop and looked at it. He had put the driveshaft back in the same spot where he marked it, I saw that myself. We ended up walking the driveshaft (rotating it 90 degrees at a time) and found a spot where the vibrations were not as bad. As it is now the vibrations occur at deceleration above 70mph, and is worse under part-throttle deceleration. There is no noticeable vibration during acceleration below 110mph, I did not try to go any faster than that yesterday. The vibrations disappear as soon as I get to speeds below 70mph or start accelerating again. There is absolutely no gear whine, and the gears meshed perfectly in the middle from what we saw using the marking compound.

The mechanic gave me a 3 year warranty on the labor and is willing to do whatever it takes to make his customer satisfied, it just sucks that the shop is almost 3 hours away, which means 1.5 tanks of gas to make the roundtrip. He thinks the driveshaft and pinion flange along with the new pinion is causing a slight imbalance, is this correct or is there something wrong with the gear install?

I love the 4.10 gears so far. I have put 250 highway miles on them, but have not gotten on them yet. As mentioned everything is as smooth as can be below 70mph now, no vibrations at all. There is absolutely no whine from the gears at any speed, only some vibrations at deceleration above 70mph.
 

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Discussion Starter #3
Im sure that the guy already did this. But are all the bolts torque down enough?
Yes, the bearing caps on the differential carrier are torqued properly, so is the pinion nut and the driveshaft bolts. I read online that an aluminum driveshaft fixed this issue for others with the same symptoms, but some say the pinion bearings are bad or have the wrong preload when this occurs. I am not sure which to believe, but we checked the pinion preload two times yesterday and drove it some and checked it again.
 

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The aluminum drive shaft would be a nice upgrade. All that comes to mind is the old crush sleeve. But that shouldn't be a problem if pinion preload is set right.
 

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Discussion Starter #5
The aluminum drive shaft would be a nice upgrade. All that comes to mind is the old crush sleeve. But that shouldn't be a problem if pinion preload is set right.
That's why I am going to try to check it myself one day soon.

Any other suggestions people?
 

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Discussion Starter #6
I have had three shops look at it, without tearing the rear end apart. One shop told me it was clutch chatter, which I have a hard time believing. The two other shops pretty much said the same thing: Too much backlash or the pinion depth is off. I talked to the shop who did the work, I am driving up there next Friday and he will fix it for me under warranty.

Since I have to make the three hour drive I am planning on having new control arms installed at the same time, he gave me a great deal to compensate for my gas expenses of driving to and from the shop for the warranty work. Money is tight, so I am leaning towards the SR Performance (AM) or SVE (LMR) rear control arm kit with polyurethane bushings, as they are identical. Both vendors sell them for $140 with free shipping, and I have discount codes for both. Does anyone have any real experience with the quality of these? Neither lists the steel type, so I'm afraid it is just some cheap steel with poor welds that will break after a few years. I really want the UPR chrome-moly kit with polyurethane bushings, but for $280 it is a little on the expensive side...
 

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I have those control arms (though I got mine from Summit Racing) and I'm happy with them. I had no wheel hop at the track and they definitely stiffen up the rear end. You will like them. For the money, they are good control arms. If you can swing UPR or MM go with them, but for a DD that not making 400+ to the wheels, they are completely fine.

Sorry to hear about your gear install. Seems a lot of people have issues. When I do mine, my dad and I will be installing them ourselves...Keep us updated!
 

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Discussion Starter #8
I have those control arms (though I got mine from Summit Racing) and I'm happy with them. I had no wheel hop at the track and they definitely stiffen up the rear end. You will like them. For the money, they are good control arms. If you can swing UPR or MM go with them, but for a DD that not making 400+ to the wheels, they are completely fine.

Sorry to hear about your gear install. Seems a lot of people have issues. When I do mine, my dad and I will be installing them ourselves...Keep us updated!
I did some more research, and apparently the UPR control arms have had quite a few problems. Because of my tight budget I will probably end up getting the SVE kit from LMR. I might just get the J&M LCAs and just replace the bushings in the UCAs, seems like non-adjustable aftermarket UCAs do no good except look better.

It sucks, but I have no whine at all, which is kind of weird. I will keep you updated!
 
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