8.8 whine and vibration

[black2009v6]

I recently bought an 8.8 off a 2013 GT with 3.73 gears to put in my 2009 V6. I had my mechanic install the flange for me and thought it would be as simple as that.

After taking it out for a drive I realized that I got a lot of whine only when decelerating in gear (no whine when decelerating in neutral) and bad vibrations at speeds above ~80 mph. Once I get the vibrations they don’t stop until I slow back to around 40 mph regardless if I’m in gear or neutral. I’m curious if anybody has any idea why this is occurring.

I plan on going back to my mechanic and having him relook everything over tomorrow but would like possible suggestions from you guys so I can let him know.


Sent from my iPhone using Tapatalk

 

[ChewyR]

Were the 3.73 gears installed from the factory? Getting gears right is a bit of an art, a novice can put them in, but setting them up correctly requires expertise. If the flange was swapped without using a new crush sleeve the bearing preload may not be correct. The vibration could be related, or it could be something else, hard to say.

 

[black2009v6]

To my knowledge the gears were from the factory.
Not sure if a new crush sleeve was installed but I’ll be sure to ask. If there wasn’t a crush sleeve installed how hard is it to install? Would it require draining out the diff again?


Sent from my iPhone using Tapatalk

 

[LarryJM]

I spend a ton of money getting 3.55 gears right in a 440 6pak. Sorry guys about the Mopar. One thing I learned after several 1000 dollars, once the gears whine you must start all over with a new set of gears and everything else or your just paying labor costs with no real results. My problem was the preload backlash. The guy setting the gears up, who thought he was the Gods gift to restoration, didn't understand that the gears need to be tight against each other in a new install. Meaning no backlash at all and the correct backlash happens in the first mile. He spent an hour getting the right backlash when in fact the backlash happens only after the job is done and gear lube is in the rear end. What would happen is the backlash of .10 after a mile is now .2 which means whine city. He said I was driving it too hard in the first mile and not his fault.

 

[Juice]

I spend a ton of money getting 3.55 gears right in a 440 6pak. Sorry guys about the Mopar. One thing I learned after several 1000 dollars, once the gears whine you must start all over with a new set of gears and everything else or your just paying labor costs with no real results. My problem was the preload backlash. The guy setting the gears up, who thought he was the Gods gift to restoration, didn't understand that the gears need to be tight against each other in a new install. Meaning no backlash at all and the correct backlash happens in the first mile. He spent an hour getting the right backlash when in fact the backlash happens only after the job is done and gear lube is in the rear end. What would happen is the backlash of .10 after a mile is now .2 which means whine city. He said I was driving it too hard in the first mile and not his fault.

I've swapped plenty of 8.8 gear sets, and NEVER ever had the backlash change after install from gears "breaking in". I have also installed a few USED gear sets successfully.

OP, Was the vibration there from the beginning, or did it get progressively worse? Could be something as simple as a bad Ujoin.

First thing I would do is grab the driveshaft by the diff and see if there is ANY up/down play. There cannot be any load on the driveshaft when you check. Do this check in neutral with the front wheels chocked. Jacking up the rear of the car is the best way to "unload" the drivetrain.

I have seen pinion bearings that were not fully seated at assembly 'seat' and start making noise/viberate.

I would also check pinion angle since the rear housing was swapped.

 

[black2009v6]

Okay so just got back from running a few experiments with my mechanic. He definitely felt what I was talking about and so we had the car up in the air and checked for any signs of anything being the culprit. The only thing we really found were the wheels were slightly off centered (my bad mustve tightened them incorrectly). But the strangest thing happened, once we lowered the car down and I took it back on the street, it felt more responsive and I didn’t hear nearly as much whine as before. It went from a worrying loud noise to just noticeable.

Secondly, the vibration was still there at higher speeds. When I get some free time, I’m going to remove the wheels and check the rotors and make sure they’re on correctly just to be safe and check for drive shaft play. I’m curious if the vibration is a result of stock v6 driveshaft hitting it’s limit earlier due to the 3.73 gears.

Whats weirdest to me is that when we had my car up in the air and he got the wheels moving and then let off the gas while in gear, there was no whine whatsoever, but when its on the street the whine is still there. So I’m not sure what to make of that honestly. But like I said I will keep double checking everything that could be possibly causing this until I find a definite answer.


Sent from my iPhone using Tapatalk

 

[LarryJM]

I've swapped plenty of 8.8 gear sets, and NEVER ever had the backlash change after install from gears "breaking in". I have also installed a few USED gear sets successfully.

OP, Was the vibration there from the beginning, or did it get progressively worse? Could be something as simple as a bad Ujoin.

First thing I would do is grab the driveshaft by the diff and see if there is ANY up/down play. There cannot be any load on the driveshaft when you check. Do this check in neutral with the front wheels chocked. Jacking up the rear of the car is the best way to "unload" the drivetrain.

I have seen pinion bearings that were not fully seated at assembly 'seat' and start making noise/viberate.

I would also check pinion angle since the rear housing was swapped.

I have no idea if there is a backlash preload requirement on an 8.8. I do know whine is very hard to get rid of. Then I did have in my 2014 Mustang GT what sounded like mid speed bearing noise that completely disappeared with a new set of tires.

 

[702GT]

I've done a few sets of used gears, it's all about preload and backlash. 3.73's have always been noisey every time I've installed them, not sure what it's about. Depending on the level of whine, it's hard to say. Gear issues are hard to diagnose without being in-person. I've never had vibration associated with a gear install, I would have to say if it's gear related, it's very bad. I would think there'd be a lot of noise accompanied with a vibration, though? I assume you're using the axels it came with as well. Did it come from a wrecked car by chance?

 

[ChewyR]

Did you find out about the crush sleeve? If you changed the pinion flange without putting a new one in, it is all but impossible to hold bearing preload. This causes the pinion to shift ever so slightly (or worse) which is why it whines under load, but not when it's in the air.

 

[black2009v6]

I've done a few sets of used gears, it's all about preload and backlash. 3.73's have always been noisey every time I've installed them, not sure what it's about. Depending on the level of whine, it's hard to say. Gear issues are hard to diagnose without being in-person. I've never had vibration associated with a gear install, I would have to say if it's gear related, it's very bad. I would think there'd be a lot of noise accompanied with a vibration, though? I assume you're using the axels it came with as well. Did it come from a wrecked car by chance?

It did come from a wrecked car but I was sure to have the axles checked because I didn’t want to put money into a rear end that had any damage from a crash. Everything as far as I know is straight and true.


Sent from my iPhone using Tapatalk

Did you find out about the crush sleeve? If you changed the pinion flange without putting a new one in, it is all but impossible to hold bearing preload. This causes the pinion to shift ever so slightly (or worse) which is why it whines under load, but not when it's in the air.

Completely skipped my mind when I was with him earlier. I’ll go back and be sure to ask as soon as possible. Just out of curiosity how hard is it to put in a new crush sleeve? If it requires taking the diff apart, would it be better to just pick up a new sleeve from my local dealership and take it to a differential shop?


Sent from my iPhone using Tapatalk

 

[ChewyR]

I found this picture. I have personally never changed the crush sleeve without disassembling everything. But it looks as though you could just pull the flange, seal, oil slinger, bearing, and potentially fish it out the front.

 

[Totheboards]

Agree with 3.73 tending to be noisy. You can sometimes get away without using a new crush sleeve if all you're doing is changing a pinion seal or flange. Proper preload on the bearings is defined in running torque. I use a 1/4" drive beam style torque wrench when I set it up. You want to measure running torque while turning the pinion without the carrier (ring gear) installed. Pinion bearing running torque with used bearings is 0.9-1.6 Nm (8-14 lb-in), and new bearings is 1.8-3.2 Nm (16-28 lb-in.) If you're reading is low, tighten the pinion nut a bit more. I've never measured how much torque it takes to crush the sleeve to the proper bearing preload, but I'd say it's probably in the 300-400 lb-ft range with a new sleeve.

Also, if you have poly bushings in your control arms, you're going to hear any noise that the soft factory bushings may have concealed.

FRPP spec for ring gear backlash is .008 - .012". You're also going to need the correct tooth depth defined by the pinion shim and carrier shims. Juggling act but fun.

https://performanceparts.ford.com/download/instructionsheets/FordInstShtM-4209-8.pdf

 

[Shaffe]

I haven't seen this mentioned yet, but what kind of gear oil is in it? When I had my last set of 4.10s installed I had a bit of a whine. Shop took it apart and rechecked everything and that cleared about 90% of the whine I could still hear it faintly. Ended up having to add some friction modifier to it, and that cleared it up.

 

[Juice]

Most gear noise is due to incorrect tooth contact pattern, but that will not cause a vibration. To adjust tooth contact pattern, the pinion depth needs to be adjusted. (the shim under the larger pinion bearing). Most gear installs, the shim is just reused from the old gear set. This method works without issues MOST OF THE TIME. If the contact pattern test shows adjustment is needed, the pinion shim needs to be changed. Cannot affect tooth contact pattern by setting backlash (shimming the carrier). None of this causes vibrations.

 

[black2009v6]

I haven't seen this mentioned yet, but what kind of gear oil is in it? When I had my last set of 4.10s installed I had a bit of a whine. Shop took it apart and rechecked everything and that cleared about 90% of the whine I could still hear it faintly. Ended up having to add some friction modifier to it, and that cleared it up.

Royal purple 75w140, bought it as part of a set that included a bottle of friction modifier.


Sent from my iPhone using Tapatalk

 

[LarryJM]

Most gear noise is due to incorrect tooth contact pattern, but that will not cause a vibration. To adjust tooth contact pattern, the pinion depth needs to be adjusted. (the shim under the larger pinion bearing). Most gear installs, the shim is just reused from the old gear set. This method works without issues MOST OF THE TIME. If the contact pattern test shows adjustment is needed, the pinion shim needs to be changed. Cannot affect tooth contact pattern by setting backlash (shimming the carrier). None of this causes vibrations.

If I remember correctly, the pinion is marked a + or - number. You look at the old pinion number and the new pinion number and you can figure out the shim size.

 

[Juice]

If I remember correctly, the pinion is marked a + or - number. You look at the old pinion number and the new pinion number and you can figure out the shim size.

Correct, IF it is there and legible. You still need to pull the old shim and measure it.

 

[LarryJM]

Correct, IF it is there and legible. You still need to pull the old shim and measure it.

Then I guess there is no need for the numbers in the first place.

 

[lenko]

Some information in here is bad, especially about having the backlash tight and it will loosen up in the first mile. You can't just slap them in and tighten them up and expect good results. Just follow this guide and you will get the right info:
https://mustangforums.com/forum/4-6...o-4-10-install-and-differential-overhaul.html

You can also consider a solid spacer and once it's set up right you never have to worry about pre=load if you have to replace a leaky pinion seal.

First set of 373 I installed in my 06 vibrated and all I did was rotate the driveshaft and bolt it up in a different position to eliminate the vibration. Others have added a washer to one of the bolts and that worked for them. It's trial and error which position or bolt.

James Adkins also had a good site for setting up gears - you might do a search for that.

I found that 4.10 gears were much easier to setup and quieter than 373 as they seem to be more forgiving as far as whine goes.

 

[LarryJM]

If the bearings are not preloaded correctly and you set the backlash under that condition, the gears will open up in a mile or so. What is the correct preload??? It's depends on who you are and how many of these you have done.