Diff swap this weekend few questions

asylum938 · Apr 11, 2018

Bought a 3.31 take off diff from shelby on Ebay to replace my 3.73s and doing the install on saturday.

1.) I have DSS axles am I correct in thinking I don't have to take these out and just remove the 6 or so bolts holding the CV on the diff side?

What's the torque spec on these bolts?

2.) The never ending friction modifier question, I picked up some Mobil 1 gear oil that says FM already added. I also went to Ford and bought the 4oz bottle of FM.

Should I skip the FM all together? Use half the bottle? Put the full 4oz in?

BmacIL · Apr 11, 2018

Whatcha doing with the 3.73 pumpkin?

I believe your assumptions are correct.

higdominator · Apr 11, 2018

asylum938 said:
Bought a 3.31 take off diff from shelby on Ebay to replace my 3.73s and doing the install on saturday.

1.) I have DSS axles am I correct in thinking I don't have to take these out and just remove the 6 or so bolts holding the CV on the diff side?

What's the torque spec on these bolts?

2.) The never ending friction modifier question, I picked up some Mobil 1 gear oil that says FM already added. I also went to Ford and bought the 4oz bottle of FM.

Should I skip the FM all together? Use half the bottle? Put the full 4oz in?

I pull my axles just because I use power tools and I like to inspect everything/lub things when I dig in back there.

However, you can just pull the bolts on the axles, just make sure to loctite them bastards back in there.

As far as the FM, use all 4oz.

VOODOO 6G · Apr 11, 2018

asylum938 said:
Bought a 3.31 take off diff from shelby on Ebay to replace my 3.73s and doing the install on saturday.

1.) I have DSS axles am I correct in thinking I don't have to take these out and just remove the 6 or so bolts holding the CV on the diff side?

What's the torque spec on these bolts?

2.) The never ending friction modifier question, I picked up some Mobil 1 gear oil that says FM already added. I also went to Ford and bought the 4oz bottle of FM.

Should I skip the FM all together? Use half the bottle? Put the full 4oz in?

Is your car an auto or a stick? If it’s an auto we just did a similar swap to a friends car. We had to get the stick shift flange for his shaft masters drive shaft. The flange on the stick shift rear end is larger than the auto and the holes don’t line up. Only by about an 1/8”. Maybe this is common knowledge.... We just pulled his axles out of the diff. They come out relatively easy. As far as friction modifier goes, not sure why you would need to add it if the fluid you bought already has it. Not saying not to though.

asylum938 · Apr 12, 2018

BmacIL said:
Whatcha doing with the 3.73 pumpkin?

I believe your assumptions are correct.

Keeping the 3.73 pumpkin for now. if the car ever goes back to stock the gears will go back in!

asylum938 · Apr 12, 2018

higdominator said:
I pull my axles just because I use power tools and I like to inspect everything/lub things when I dig in back there.

However, you can just pull the bolts on the axles, just make sure to loctite them bastards back in there.

As far as the FM, use all 4oz.

Axles went in 2,000 miles ago, so if I can just pull the bolts at the diff side I think that will save some time. everything was cleaned/lubed when they went in.

guess I'll call DSS and find out the torque spec on those bolts.

whatsup62 · Apr 12, 2018

asylum938 said:
Axles went in 2,000 miles ago, so if I can just pull the bolts at the diff side I think that will save some time. everything was cleaned/lubed when they went in.

guess I'll call DSS and find out the torque spec on those bolts.

Here was the info DSS gave me when I removed the bolts
Run a tap through the threads and use blue or red loctite torqued to 70ft. lbs.

whatsup62 · Apr 12, 2018

BmacIL said:
Whatcha doing with the 3.73 pumpkin?

I believe your assumptions are correct.

You looking for a complete 3.73 rear?

BmacIL · Apr 12, 2018

whatsup62 said:
You looking for a complete 3.73 rear?

Yes it's definitely high on my list of things to do.

asylum938 · Apr 16, 2018

Little update to this.

Finished up the swap Saturday night and everything went smooth.

I did disconnect the halfshafts on the diff side. If you are going to do this make sure you use a paint pen to help with reinstalling the bolts when putting it all back together.

Used half the bottle of friction modifier as I used mobil 1 fluid with modifier already added, seems smooth, if I get chatter I'll add the other half of the bottle

Last I changed the axle ratio with the flare tool, easiest part of the job took about 30 seconds.

TURTL3 · May 1, 2018

I guess I'll resurrect this thread to stop from starting a new one, so quick question:

I recently swapped from 3.15 to 3.55 and I get a creaking click noise when I decelerate in neutral to a stop. I know it's the diff or something in that area. It sounds like gears clicking and moving. Could I just need to add friction modifier? I bought Redline gear oil and it says that the FM is added already but I'm curious. The car drives fine, I just get that noise at low speeds and deceleration.

asylum938 · May 1, 2018

TURTL3 said:
I guess I'll resurrect this thread to stop from starting a new one, so quick question:

I recently swapped from 3.15 to 3.55 and I get a creaking click noise when I decelerate in neutral to a stop. I know it's the diff or something in that area. It sounds like gears clicking and moving. Could I just need to add friction modifier? I bought Redline gear oil and it says that the FM is added already but I'm curious. The car drives fine, I just get that noise at low speeds and deceleration.

factory axles? I know alot of people have issues with the Axle nuts not being tight enough and causing a clicking/popping sound. just a guess as this may not be the same noise you are hearing.

TURTL3 · May 1, 2018

Yeah factory axles. I'll try the axle nuts too, I read about that. I've never actually done a fluid swap on a diff before ever so the whole FM thing was confusing me. I may add some just because, I guess it wouldn't hurt right? But I will check those axle nuts too

johnson.ba · May 1, 2018

TURTL3 said:
Yeah factory axles. I'll try the axle nuts too, I read about that. I've never actually done a fluid swap on a diff before ever so the whole FM thing was confusing me. I may add some just because, I guess it wouldn't hurt right? But I will check those axle nuts too

You only need to use friction modifier on clutch type limited-slip differentials. Open or mechanical LSD like the torsen don't require friction modifier.

Diff swap this weekend few questions

asylum938

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BmacIL

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higdominator

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VOODOO 6G

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asylum938

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asylum938

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whatsup62

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whatsup62

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BmacIL

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asylum938

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TURTL3

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asylum938

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johnson.ba

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