alpine.adrenaline

Alright, I just went from a 3.55 gear ratio to 4.56. The first time I picked it up, I had a loud howl from my rear end that sounded like the new gears in my Chrysler 8.25. I brought it back and the guy doing it said a bad set of gears came from the factory, so he hooked me up with a complete Ford 8.8 axle swap in exchange for my old 8.25 and some extra. I was pretty psyched because I know how durable the 8.8 is & I hate drum brakes. Before I picked it up the second time he said the humming was still there, and that it must be a bearing in my transfer case or transmission. I agreed, because my transmission was making some funny noises before I did a filter and fluid change and I knew my transfer case bearings had never been replaced- though everything looked fine when I put in the SYE. There is also a small amount of play in the front output shaft, so I'm pretty sure it needs to be serviced and that's where this awful howl must be coming from.

Here's the thing: I removed the rear driveshaft, put it in 4, and drove it to work this morning. The howl is still there, and is resonating loudly from the rear end. Remember those SonicCare Toothbrushes? It sounds like there's a giant one in my rear quarterpanel. Frequency increases with speed.

I trust this guy because he's been upfront and communicative. I know good fabwork and his perch welds on the 8.8 are great. Could two different axles really be making the same noise, or is this howl coming from my transfer case or transmission, even though it's resonating in the back? Wouldn't it need that rear shaft to resonate through? I'm about to strap myself to the underside of my jeep with a stethoscope while my buddy drives to try to narrow this down.

Demolition_x

I would put money on the gears being installed wrong or out of spec. What brand gears did you use?

bigvig

Take off the diff cover and see if there are any shavings or rubbing going on in there.

alpine.adrenaline

I don't remember the brand of gears, but he said he hadn't used them before. He had done a few 4:56 in the 8.25 but this was the first with a different brand. I don't know what was used in the 8.8.

I'm very near the 500 mile mark to drain and replace the fluid in my Dana30 after breakin, so I'll check the back when I do.
Speaking of which, both times I picked it up I spent the first 15 minutes in stop-and-go traffic under very light accelleration. Didn't drive either axle over 50mph for the first 100 miles, still haven't taken it offroad or done any heavy acceleration.

alpine.adrenaline

Do transfer cases and transmissions typically not howl if a bearing is going?

the buddmang

They would, but you would notice a change in pitch/loudness as you put a load on the trans and tcase. If you took the rear ds out and it still sounds like its coming from the rear ot could be ring/pinion noise or carrier bearings or axle bearings. Aftermarket ring/pinion sets do make more noise than a factory set, but it shouldnt be /that/ loud.

Only way to tell is to check the diff fluid for excessive metal (some is normal) and check the wear pattern on the ring and pinion.

Agent_Oragnge

cheap diff check. open up the fill hole and take an extendZ magnet. poke around awhile down at the bottom. any filings or (worse case senerio) busted teeth will come up on the magnet. be patient that magent will get stuck to everything in there.

alpine.adrenaline

I'll try that. My rear DS is still off, so I got it up to 30 and put it back into 2wd to let it coast. Still howled and its all from the back, so I guess that isolates the rear axle. I can underastand some whine coming from new gears but I can't even drown this sound out with the blower on full blast. I guess I'm going to have to take it to another shop to get another opinion on the gears.

RenixMudbox

dude thats your axel howling get your gears done right and take him to small claims court with the bill. obviously he didnt do it right just my 2c

N20jeep

im going to put money on him setting up the contact pattern wrong in the axles. that will cause a howl/whine sound.

ct67_72

its really odd to have the exact same problem with 2 axles. Im not saying its not possible, Im just saying were looking past the obvious here.
does the noise change with load? like from neitral to accelerating? in gear no throttle?
chassis noises are funny htings and resonate all over a vehicle. Be sure what your talking about before you go bashing a guy who seemed to be trying to help you.
If your driving with no rear shaft and the sound changes at all from a difference in load its not the rear.
If it does change with load, install rear shaft, pull front and try again.
hell, put the front end up on jackstands with no rear shaft and run it up to speed. that will take the rear completely out of the equation.

alpine.adrenaline

I don't think it will come to that. This guy has been pretty helpful and accomodating.
I'm not bashing him at all, I'm just trying to get to the root of the problem. He said both of his gear sets were setup correctly, and I believe him. I just don't know what else it could be.
The sound doesn't change with a difference in load when the rear shaft is removed. It starts off as a dull roar and gets louder as I go faster. It really sounds like I have some serious mudding tread on my rear tires. I'm going to have a driveline shop take a look at it tomorrow. I want a second opinion from an accredited business.

alpine.adrenaline

I feel like I'm filling up my own thread, but thanks for everyone's input so far. Can anyone recommend a good dial indicator, or a good place to get one? I've been researching regearing all day and I may try to dive in there myself...

ct67_72

But is there a difference with the shaft in? You need to make sure you troubleshoot it before you dive into the setup. Especially if you've never done it before. And if its the same with 2 rears.

alpine.adrenaline

It doesn't make a difference whether I remove the front or the rear driveshaft.