Bye Bye 4.10s... Hello 3.55s

[Flyn]

Some of you may know my rear end decided to start eating the gears last week. I wasn't sure what the vibration/rumble was so Sutton diagnosed it as the rear end needing a rebuild. That's expensive so I was looking for cheaper options.

I talked with Doug at Sutton and he let me know that Bruce [Black Cobra, Sutton build...] was trying to sell his IRS. Low miles and reasonable price. I bought it and brought it and my car out to Dan's. He and Lyle swapped the IRSs today. I still need to pull out my speed calibrator to fix the speedo and the car needs to be aligned but it is running well and the vibration is gone. Now I have to get used to the difference in gear ratios. Going from 4.10 to 3.55 is quite a difference.

By the way, Dan was right when he told me 4.10s would be too much for the street with 500 hp. I can actually get traction again with the 3.55s. With the 4.10s, you can't put the power to the ground without sticky drag radials.

My thanks to Dan, Lyle and Doug and everyone who helped one way or another. :biggthump

Shelby Guy has dibs on my IRS but I'll put it up for sale here if he doesn't take it.

Click to read more...

 

[VenomInside]

:headbang: LDC :headbang:

 

[Mr. Unknown]

4.10s too much? We shall see...

I guess so. How many miles were on them?

 

[Flyn]

I guess so. How many miles were on them?

25,000 - 30,000 maybe? I'd have to look up the receipt.

 

[Mr. Unknown]

damnnnn!

 

[doodad]

i love the feeling of 3.55s on the highway. I guess i wouldn't go any higher than 3.90s if i ever do gears!

 

[hj16]

I never understood why people put gears in these cars who aren't track rats... guess live and learn huh Clifford?

 

[Flyn]

I never understood why people put gears in these cars who aren't track rats... guess live and learn huh Clifford?

4.10s were great with the mildly modified 400 rwhp motor but too little traction on the street with 500 rwhp.

 

[rdsnake]

3.73 FTW!!!

Who installed the 4.10s any chance they installed them incorrectly......?

 

[1badass96gt]

3.73 FTW!!!

Who installed the 4.10s any chance they installed them incorrectly......?

Not likely the installer after 25K miles, issues would have probably showed up earlier.

 

[rdsnake]

Not likely the installer after 25K miles, issues would have probably showed up earlier.

No, not really...

 

[Wiked03]

I still love my 4.10s... first gear is pretty worthless on the street but I can usually hook the nittos in second. I may have to eventually go down to a 3.73/3.90 so I don't have to shift 5th at the strip though.

 

[1MEANGT]

Nice, glad you got it worked out Cliff!!!

 

[Sharkster]

Some of you may know my rear end decided to start eating the gears last week. I wasn't sure what the vibration/rumble was so Sutton diagnosed it as the rear end needing a rebuild. That's expensive so I was looking for cheaper options.

I talked with Doug at Sutton and he let me know that Bruce [Black Cobra, Sutton build...] was trying to sell his IRS. Low miles and reasonable price. I bought it and brought it and my car out to Dan's. He and Lyle swapped the IRSs today. I still need to pull out my speed calibrator to fix the speedo and the car needs to be aligned but it is running well and the vibration is gone. Now I have to get used to the difference in gear ratios. Going from 4.10 to 3.55 is quite a difference.

By the way, Dan was right when he told me 4.10s would be too much for the street with 500 hp. I can actually get traction again with the 3.55s. With the 4.10s, you can't put the power to the ground without sticky drag radials.

My thanks to Dan, Lyle and Doug and everyone who helped one way or another. :biggthump

Shelby Guy has dibs on my IRS but I'll put it up for sale here if he doesn't take it.

+1 on getting used to the 3.55's from 4.10's. The plus for me is my turbos come online real quick to make up for it

 

[Dana]

We didn't have time or the energy to disassemble the carrier to determine the exact cause of failure, but we are definitely interested in knowing.
So, to who ever buys this IRS, please let us know what you find when you pull the cover off.
I'm just guessing here, but it may be the pinion bearing.

Thanks,
Dan

 

[Flyn]

Shelby Guy is the new owner of my IRS. If anyone can figure out what's wrong with it, he can.

I'm guessing here but I have had 80 mph+ vibration for nearly the entire life of the car. It's been in for service several times at various shops with no success at finding the problem. With the replacement rear end, the vibration is gone. :headbang:

My guess is there was something wrong with the gears/bearings/shims/etc. in the casing that caused the vibration. Sutton swapped the halfshafts during their diagnosis so they weren't the problem. Wasn't the drive shaft or wheel bearings either. Leads me to believe that the vibration was caused by an imbalance or problem with some of the gears/bearings/shims/etc. in the rear end for most of the car's life, even before the 4.10s were installed. I'd guess it was a factory problem that was just never found.

 

[Sharkster]

Shelby Guy is the new owner of my IRS. If anyone can figure out what's wrong with it, he can.

I'm guessing here but I have had 80 mph+ vibration for nearly the entire life of the car. It's been in for service several times at various shops with no success at finding the problem. With the replacement rear end, the vibration is gone. :headbang:

My guess is there was something wrong with the gears in the casing that caused the vibration. Sutton swapped the halfshafts during their diagnosis so they weren't the problem. Wasn't the drive shaft or wheel bearings either. Leads me to believe that the vibration was caused by an imbalance or problem with some of the gears in the rear end for most of the car's life, even before the 4.10s were installed. I'd guess it was a factory problem that was just never found.

imbalance in the driveshaft??

 

[Sharkster]

shit scratch that.... now I see it wasnt sorry

 

[Mystic Terminator]

Driveline vibration is rarely caused by gears.

 

[Flyn]

Driveline vibration is rarely caused by gears.

Same driveshaft now and the vibration is gone.

That is actually the third driveshaft the car has had and the vibe has always been there. Symptoms lead me to believe that something inside the casing was causing the vibe. Either gears, shims or whatever. I'm no expert on the internal components but the clues lead that way.

 

[rdsnake]

Cliff who installed the 4.10's?

 

[Flyn]

Cliff who installed the 4.10's?

Sutton put them in a few years ago. I had the 80 mph+ vibe before the 4.10 gears were installed as well as after.

Edit-Tirapelli Ford originally looked for the vibe causes but didn't find them. Sutton also checked the vibe out but didn't get the car up fast enough to vibrate if I remember right.

 

[rdsnake]

Sutton put them in a few years ago. I had the 80 mph+ vibe before the 4.10 gears were installed as well as after.

Edit-Tirapelli Ford originally looked for the vibe causes but didn't find them. Sutton also checked the vibe out but didn't get the car up fast enough to vibrate if I remember right.

Well all that matters is the vib is gone.

When I had my bent input shaft, I hated the car, I didn't even want to drive it...When it was fixed it was like brand new again
:headbang:

 

[Flyn]

Well all that matters is the vib is gone.

When I had my bent input shaft, I hated the car, I didn't even want to drive it...When it was fixed it was like brand new again
:headbang:

I agree. It is a great feeling to take the car up to 80 and not feel any vibe.

 

[svtslowcar]

I still love my 4.10s... first gear is pretty worthless on the street but I can usually hook the nittos in second. I may have to eventually go down to a 3.73/3.90 so I don't have to shift 5th at the strip though.

im getting 3.90's next month so ill let you know how they are.