Thinking of rebuilding my rear axle. What to use for parts?

builttodrive

Active Member
Established Member
Joined
Oct 26, 2014
Messages
586
Location
Sioux Falls, SD
Digging this one back up. This project got put on hold but I am now starting to tear into it and getting ready to rebuild. I will plan to weld the axle tubes and add a new 3.73 ring and pinion to hopefully help my gear whine. The car has a little over 700whp and will primarily be a street car but I may take it to the drag strip a little and possibly try an autocross.

Anyone have any recommendations on what parts I should be putting in the rear axle? I'd like to have a solid axle without gear whine but I don't need to get carried away and overbuild or over spend.
 

Mojo88

"Hammer" Time
Established Member
Joined
Jan 30, 2017
Messages
1,319
Location
RI
I just did mine (2010 8.8) - completely. I replaced every moving part, except for the Moser axles. I used all Ford parts, with 3.55 Ford Racing R&P. My car makes 625rwhp. The old diff had numerous problems (chipped spider gears among them) and howled like a banshee when driving. The new setup is quiet as a mouse.

I had to buy a carrier because the old one had spun the bearings. I have included a couple of pics below. The previous owner had run slicks on the car a few times, and that probably over-stressed the Trac-Lok, which is rated to about 700hp I think. I ended up just buying another Trac-Lok because I knew I wasn't going to ever put slicks on it, but if I was, then I would have bought something stouter, so my advice is do NOT utilize a Ford Trac-Lok carrier. Prior to pressing new bearings onto the new Trac-Lok, I used some Loctite Retaining Compound to help prevent that issue with the new carrier, and with your power level, I would recommend utilizing Retainer Compound to help hold the bearings onto the carrier. The bearings are too small for big power IMHO. Certainly seems like a weak point.

carrierhub1.JPG

carrierhub2.JPG

diff89.jpg
 
Last edited:

Robert M

800 HORSE FUN!!
Established Member
Joined
May 15, 2003
Messages
9,157
Location
Sunny, Fla.
When I did my 2008 8.8 axle housing de-rust and restoration I replaced the oem CF clutch posi unit with a True-Trac and up graded the oem axle to Moser Street Axles.....

0019-1.jpg


I also added a Shelby girdle/cover and Baer Extreme 6S rear brakes......while it was all apart.

0063-zpsfb08ff58.jpg


The FRPP 3.73's that Shelby had installed during the Super Snake upgrade were removed and reset with the True-Trac with no noise issues after the reset.

R
 

builttodrive

Active Member
Established Member
Joined
Oct 26, 2014
Messages
586
Location
Sioux Falls, SD
I just did mine (2010 8.8) - completely. I replaced every moving part, except for the Moser axles. I used all Ford parts, with 3.55 Ford Racing R&P. My car makes 625rwhp. The old diff had numerous problems (chipped spider gears among them) and howled like a banshee when driving. The new setup is quiet as a mouse.

I had to buy a carrier because the old one had spun the bearings. I have included a couple of pics below. The previous owner had run slicks on the car a few times, and that probably over-stressed the Trac-Lok, which is rated to about 700hp I think. I ended up just buying another Trac-Lok because I knew I wasn't going to ever put slicks on it, but if I was, then I would have bought something stouter, so my advice is do NOT utilize a Ford Trac-Lok carrier. Prior to pressing new bearings onto the new Trac-Lok, I used some Loctite Retaining Compound to help prevent that issue with the new carrier, and with your power level, I would recommend utilizing Retainer Compound to help hold the bearings onto the carrier. The bearings are too small for big power IMHO. Certainly seems like a weak point.

View attachment 1678150
View attachment 1678151
View attachment 1678152

Was this with a GT500 carbon fiber trac-lok or standard Mustang GT? Thanks for the info!
 

builttodrive

Active Member
Established Member
Joined
Oct 26, 2014
Messages
586
Location
Sioux Falls, SD
When I did my 2008 8.8 axle housing de-rust and restoration I replaced the oem CF clutch posi unit with a True-Trac and up graded the oem axle to Moser Street Axles.....

View attachment 1678219

I also added a Shelby girdle/cover and Baer Extreme 6S rear brakes......while it was all apart.

View attachment 1678220

The FRPP 3.73's that Shelby had installed during the Super Snake upgrade were removed and reset with the True-Trac with no noise issues after the reset.

R

I'm wondering if it's in my best interest to make upgrades. I don't want to do it twice of course but I wanted to do it right without braking the bank also. I'm sure most of the use will be with a fairly sticky tire on the street but I have always wanted to throw a set of drag radials on it and try my luck at the track. Do you like the TrueTrac? I have one in another one of my vehicles but It's not making anywhere near this much power and I was told from others the true trac may not hold up at my power levels.
 

Mojo88

"Hammer" Time
Established Member
Joined
Jan 30, 2017
Messages
1,319
Location
RI
Was this with a GT500 carbon fiber trac-lok or standard Mustang GT? Thanks for the info!

My car is 2010 Roush, in other words, a Mustang GT with a bunch of upgrades. The Trac-Lok I used was for Mustang GT.

I'm no diff 'expert' by any means, but after seeing the carnage and wear inside my 8.8, IMHO the 8.8 is not designed for big power and slicks, and 625rwhp is not exactly huge power.

EDIT: I did notice some very poor assembly setup as I was taking apart my 8.8, so perhaps that contributed to the numerous issues. Whoever put it together the last time did a horrible job.
 

Robert M

800 HORSE FUN!!
Established Member
Joined
May 15, 2003
Messages
9,157
Location
Sunny, Fla.
I'm wondering if it's in my best interest to make upgrades. I don't want to do it twice of course but I wanted to do it right without braking the bank also. I'm sure most of the use will be with a fairly sticky tire on the street but I have always wanted to throw a set of drag radials on it and try my luck at the track. Do you like the TrueTrac? I have one in another one of my vehicles but It's not making anywhere near this much power and I was told from others the true trac may not hold up at my power levels.

There have been some, I think I can even say many, who have a True-Trac and drag race their car on this forum. If you get into the high HP world and slicks, it may not be the best choice, but for recreational drag racing and street use, I have heard good comments from the guys who do drag race their car. Me personally, I am a street car guy with occasional sprints, so I do not test the True-Trac limits in my usage.

When I took the cover off of my 8.8 during the de-rust and restoration I found an amount of "black muck" in the very bottom of my center housing, this would be fluid that would not be emptied in a normal cover removal because it is lower in the housing, it required sucking it out and using a rag to clean out the residue. I found that the "black muck" seemed to be the heavier debris from the CF clutch pack in the posi unit........<<This was at 600 original miles, so I can imagine the amount of "black muck" in the bottom/sump of a higher mile GT500. I decided from that point that I did not want a "clutched" posi unit and instead a posi unit that did not have friction plates to wear and put debris in the bottom of my 8.8, that fine debris also somewhat circulates through all of the fluid, carrier bearings, axle bearings, pinion bearings, pinion and ring contact, etc. So by eliminating the wear factor of clutch discs, I should keep cleaner fluid in my 8.8.

BTW - That "black muck"..........it was like a liquid graphite in the very bottom of my 8.8 which indicates to me that yes, at least some of it was CF wear from that oem posi unit.

The Shelby cover/girdle is like the FRPP G1 cover and does require a panhard relocation brkt. and the FRPP G2 does not and is a nice piece, but I kind of like the "Shelby American" engraving....so I went that direction.

The Moser Street Axles.....they are C-clip design just like oem, so if C-clips are an issue for your usage, the Moser Street Axles would not be the best choice. I saw a post with the picture below on this forum a few years ago.......

D4-D6-E02-F-0-D44-4-A8-A-9-C63-7-CC76-AB77-DE3-2848-000002896-CFCB94-B-zpse767e4a41-zpsb5f01805.jpg


The oem axles "neck down" toward the spline end, that is where they will break it sufficient traction is achieved. I decided, while I was there and my 8.8 was apart, to upgrade the axles. The Moser Streets do not reduce diameter but instead are the same larger size the full length.

The rear Baer Extremes....I added them to match the front that Shelby had installed. It was a visual thing for me when the car is viewed from the side.

R
 
Last edited:

Robert M

800 HORSE FUN!!
Established Member
Joined
May 15, 2003
Messages
9,157
Location
Sunny, Fla.
Was this with a GT500 carbon fiber trac-lok or standard Mustang GT? Thanks for the info!

.........^^^^ and are they both 31 spline? I know the GT500 is, but I am not sure about the GT? maybe it is also. I do remember the Bullitt Mustang (based on a Mustang GT), got an axle upgrade from the factory to GT500 level and also 3.73's I believe....

R
 

SCGallo2

Balanced performance
Established Member
Premium Member
Joined
Mar 4, 2014
Messages
1,185
Location
Southern MD
When I did my 2008 8.8 axle housing de-rust and restoration I replaced the oem CF clutch posi unit with a True-Trac and up graded the oem axle to Moser Street Axles.....

This will be my next major project, just looking to freshen up the rear after many years of spirited driving. Sand blasting the rear axle assembly, welding axle tubes, and painting or powdercoating in black semi-gloss. Eaton TrueTrac 31 or 33 spline differential with Moser Street axles, 3.55 ring and pinion, all new bearings and seals. I already have a Ford Racing diff cover with bearing cap supports. I am running Nitto NT555RII drag radials on the rear for traction on the street, but I have no plans on repeatedly shocking the drivetrain with 1st gear dig launches.
 

Mojo88

"Hammer" Time
Established Member
Joined
Jan 30, 2017
Messages
1,319
Location
RI
.........^^^^ and are they both 31 spline? I know the GT500 is, but I am not sure about the GT? maybe it is also. I do remember the Bullitt Mustang (based on a Mustang GT), got an axle upgrade from the factory to GT500 level and also 3.73's I believe....

R

Yes, my Moser axles are 31 spline, very nice pieces.

You have a very nice rear end (don't take that too personally, haha). I probably should have done that (sandblast/paint) to mine, as my rear is the ONLY rusty part on the entire car. I don't understand why Ford wouldn't have shot a quick coat of paint onto it. They painted everything else.
 

builttodrive

Active Member
Established Member
Joined
Oct 26, 2014
Messages
586
Location
Sioux Falls, SD
This will be my next major project, just looking to freshen up the rear after many years of spirited driving. Sand blasting the rear axle assembly, welding axle tubes, and painting or powdercoating in black semi-gloss. Eaton TrueTrac 31 or 33 spline differential with Moser Street axles, 3.55 ring and pinion, all new bearings and seals. I already have a Ford Racing diff cover with bearing cap supports. I am running Nitto NT555RII drag radials on the rear for traction on the street, but I have no plans on repeatedly shocking the drivetrain with 1st gear dig launches.

What gears do you have or have you tried? I have 3.73's in the car now and planned for 3.73's again but thought a 3.55 wouldn't be a bad choice also.
 

builttodrive

Active Member
Established Member
Joined
Oct 26, 2014
Messages
586
Location
Sioux Falls, SD
There have been some, I think I can even say many, who have a True-Trac and drag race their car on this forum. If you get into the high HP world and slicks, it may not be the best choice, but for recreational drag racing and street use, I have heard good comments from the guys who do drag race their car. Me personally, I am a street car guy with occasional sprints, so I do not test the True-Trac limits in my usage.

When I took the cover off of my 8.8 during the de-rust and restoration I found an amount of "black muck" in the very bottom of my center housing, this would be fluid that would not be emptied in a normal cover removal because it is lower in the housing, it required sucking it out and using a rag to clean out the residue. I found that the "black muck" seemed to be the heavier debris from the CF clutch pack in the posi unit........<<This was at 600 original miles, so I can imagine the amount of "black muck" in the bottom/sump of a higher mile GT500. I decided from that point that I did not want a "clutched" posi unit and instead a posi unit that did not have friction plates to wear and put debris in the bottom of my 8.8, that fine debris also somewhat circulates through all of the fluid, carrier bearings, axle bearings, pinion bearings, pinion and ring contact, etc. So by eliminating the wear factor of clutch discs, I should keep cleaner fluid in my 8.8.

BTW - That "black muck"..........it was like a liquid graphite in the very bottom of my 8.8 which indicates to me that yes, at least some of it was CF wear from that oem posi unit.

The Shelby cover/girdle is like the FRPP G1 cover and does require a panhard relocation brkt. and the FRPP G2 does not and is a nice piece, but I kind of like the "Shelby American" engraving....so I went that direction.

The Moser Street Axles.....they are C-clip design just like oem, so if C-clips are an issue for your usage, the Moser Street Axles would not be the best choice. I saw a post with the picture below on this forum a few years ago.......

View attachment 1678291


The oem axles "neck down" toward the spline end, that is where they will break it sufficient traction is achieved. I decided, while I was there and my 8.8 was apart, to upgrade the axles. The Moser Streets do not reduce diameter but instead are the same larger size the full length.

The rear Baer Extremes....I added them to match the front that Shelby had installed. It was a visual thing for me when the car is viewed from the side.

R

Good info! I also have the Ford Racing aluminum rear cover and my Griggs Racing torque arm with Watts link is attached through it. A rear brake upgrade would be a nice touch but I don't know what size wheels I want to run for my drag radials and don't want to limit myself to large wheel sizes.
 

Robert M

800 HORSE FUN!!
Established Member
Joined
May 15, 2003
Messages
9,157
Location
Sunny, Fla.
Good info! I also have the Ford Racing aluminum rear cover and my Griggs Racing torque arm with Watts link is attached through it. A rear brake upgrade would be a nice touch but I don't know what size wheels I want to run for my drag radials and don't want to limit myself to large wheel sizes.

I have my original 20" Alcoa's widened to 10" and 12", plus some other Shelby wheels that I have test fitted which also fit the big Baer Extremes. I am not sure what smaller size wheels fit the Extreme 6S calipers? Wilwoods are smaller and I would think more of the smaller size wheels would fit them......but any of these aftermarket brake upgrades are EXPENSIVE! I would never have bought the rear Baers except for the fact that Shelby had installed the Extreme 6S on the front and I wanted a matching look when the car is viewed from the side.

R
 

SCGallo2

Balanced performance
Established Member
Premium Member
Joined
Mar 4, 2014
Messages
1,185
Location
Southern MD
What gears do you have or have you tried? I have 3.73's in the car now and planned for 3.73's again but thought a 3.55 wouldn't be a bad choice also.

Stock 3.31 gears with 27.4" diameter rear tires on my 2008 at similar power level to your car. Now that I can hook the power, I want just a little more acceleration, and I don't mind the couple hundred additional RPM.

I have driven another 2008 with 3.73 gears and stock 27.1" diameter tires, and felt that it was just a little too much gear... always looking to shift to the next gear. Drove another friend's 2010 with stock 3.55 gears and stock diameter tires and thought it was perfect gearing.
 
Last edited:

builttodrive

Active Member
Established Member
Joined
Oct 26, 2014
Messages
586
Location
Sioux Falls, SD
Stock 3.31 gears with 27.4" diameter rear tires on my 2008 at similar power level to your car. Now that I can hook the power, I want just a little more acceleration, and I don't mind the couple hundred additional RPM.

I have driven another 2008 with 3.73 gears and stock 27.1" diameter tires, and felt that it was just a little too much gear... always looking to shift to the next gear. Drove another friend's 2010 with stock 3.55 gears and stock diameter tires and thought it was perfect gearing.

I had an 06 Mustang GT and an 07 Shelby GT both 5 speeds with 3.55 gears and I really like that gear in those cars. I wouldn't rule that gear out but I know I don't want to ride the clutch anymore with less gear as my Mcleod RXT doesn't like it much. The other angle is that gear calculator still put my car with a 3.89 gear for best 1/4 mile results so the 3.73 is probably a good middle ground.
 

Users who are viewing this thread



Top