Swapping in 3.55 gears may have saved my life

[Chris B.]

I took the Mustang to a Friend's shop today to have the 4.10 gears put in by the 1st owner replaced with 3.55 gears so that the car would have more top end on the road course and get better gas mileage on the highway. With the 4.10 gears and smaller diameter R comp tires, I run out of gear by 120 MPH with the 4.10's. I'd shift into 5th and the car would feel like it stopped accelerating. My previous 2008 Mustang GT pulled hard to 130+ MPH and it had about 40 less wheel HP.

I got a call from my friend that there was some unexpected damage to the rear end and I should come and look at it.

It looks like the shop that put in the 4.10 gears damaged a bearing during the install and didn't replace the bearing. The damaged bearing caused the whole diff assembly to wobble and it got worse as the bearing wore. The bearing started to wear unevenly and get noisy. As it wobbled and wore unevenly, little metal bits came out into the diff. The wobble got bad enough that it damaged the axle and pinion gear. I was lucky the bearing didn't fall apart as I was driving it. I thought the rear end noise was the typical 4.10 gear rear end noise and that's what I was told by other Mustang owners that rode in the car.

I immediately thought about going around Pocono's road course doing 130+ MPH 1' away form the wall then entering turn 1 at 120+ MPH and what would have happened if the bearing decided to puke its guts out at that moment and the rear locked up. I don't think that would buff out at all.

 

[Scott_0]

glad you caught it before things got nasty, that would not have been fun

 

[weather man]

ser·en·dip·i·ty (s

r

n-d

p

-t

)
n. pl. ser·en·dip·i·ties

1. The faculty of making fortunate discoveries by accident.
2. The fact or occurrence of such discoveries.
3. An instance of making such a discovery.

Glad you did find the issue!

 

[Swarzkopf]

Holy shit man- yeah, that's some scary stuff! Glad you got it figured before something really bad happened.

 

[NickSezz]

Great you found that out now! My diff crapped out on my 05 and caused me to skid in the middle of an intersection...luckily I was on the brake and only going like 15mph.

 

[itsslow]

Damn that sucks! I'm glad you found out!

 

[stratman]

That would have been a hell of a ride!Glad you didn't take it.

 

[Makdaddy]

I never understood why people put up with whine in the rear end
if setup properly 4:10 or any other gear should not whine or make the type of noises you described


Lesson learned
Glad you found it in time

 

[OneQwkStang]

My diff went after the dealership did some warranty work. Apparently they never had the pinion right and the pinion walked during a pass at the drag strip. It was loud as hell...sounded like my motor blew.
Crappy work kills.

 

[cwhit23]

I never understood why people put up with whine in the rear end
if setup properly 4:10 or any other gear should not whine or make the type of noises you described


Lesson learned
Glad you found it in time

I agree. I have a 4:10 and it's never made noise, as well as my previous cars I never had gear whine.
But on topic, glad you found it before it caused you a problem. stuff like that can be a scary thought when you find it.

 

[Chris B.]

Yea, I guess I can consider myself lucky. At first I was disappointing at the extra time and cost, but it beats having the diff lock up at the wrong time and send my car off the road into a tree or off the track into a wall.

 

[Riptide]

They put up with it because they got tired of throwing money at it. There are people who have taken it to multiple shops and still the problem remained. Gets ridiculous at some point.


Sent from my iPhone using Tapatwat

 

[Chris B.]

I picked up the car this afternoon and I also took pics of what was left of the gears in the rear. Its amazing how many gears were missing teeth or had damaged teeth. I'll upload pics later.

 

[TGR96]

Wow! Glad to hear that they caught that. Sometimes...things just work out. Interested in seeing the carnage.

 

[Morris]

What's the going rate for a gear swap?

 

[Roadracer350]

Shops here swap gears for 350

 

[Morris]

Wow, that's a great price! What I have seen so far in the bay area is 600 to 800 bucks just for labor. I need to look around a lilttle more.

 

[Chris B.]

I forgot I never posted pictures of the diff. I didn't get many good pictures. The cell phone pics were blurry, but here are a couple pictures. There were also missing from the ring gear in various places. The pinion gear had an unusual wear pattern to it also. I also ended up having one axle replaced because it was wearing funny on the end near the diff.

 

[Wes06]

Holy shit. Damn good thing it was caught

 

[lethe]

I forgot I never posted pictures of the diff. I didn't get many good pictures. The cell phone pics were blurry, but here are a couple pictures. There were also missing from the ring gear in various places. The pinion gear had an unusual wear pattern to it also. I also ended up having one axle replaced because it was wearing funny on the end near the diff.

Thats racist....just messing with you . Im glad you didn't have a major failure that caused an accident or left you stranded. The people who told you that the noise was "normal" for 4.10s must not know a lot about gears. With that kind of damage it had to be a hell of a lot noisier then any normal 4.10 gear set would be.