Rebuild differential??

duanemyhre

Registered User
I know that there are many people out there with well over 100,000 miles on their SCs. When is it recommended that you rebuild the differential? I read 125,000. Is there a certain time they start going bad. I realize that different variables contribute to this, but I would like to get an idea for stock cars with average daily use.

Thanks,
Duane
 
If you have a 5 speed or earlier model auto trans. with a traction lock (limited slip diff) then about the only thing to re-build is the clutch pack (about $60 + labor). Otherwise if it's not noisey, leaking oil from the pinion seal or you want to change the ratio - then just change the fluid. Here you have the option of regular hypoid oil or synthetic, plus you need the friction modifier for any limited slip units. I had 247,000m on my '90 with no diff. problems. I have 195,000m on my '93 - but I lowered the ratio to 3.27 and put new clutch discs in at about 150,000m & I have 107,000m on my '94 auto and just changed the fluid for the first time.
 
Well After the shootout in E-town their are 3 or 4 of us that discovered our diff were shot. I am researching my options now, but I will be staying with the 2.73 gears.

Gary
 
I have an inner CVU boot with a tear, so I thought I would take care of my diff at the same time.
Where is the best place to buy the clutch?
Do I need any special tools to replace my clutches?

car is a 1990 with an auto trans

My project list was quite large for my car this summer, but it is slowly getting smaller.
 
http://www.corral.net/tech/drivetrain/gears.html

This link is from the Corral is for a gear install on a Stang, but has a section about trac-loc rebuild. Its an ok article, I think I had a more detailed one linked, but during a cleaning fit I deleted some links and it most have been one of them. The article said the hardest part was putting the S spring back in place.
 
supercatxr7
I had planned to change the oil in my diff and had read that if the clutches in my diff go out it would destroy my diff. I thought I would be on the safe side and change the clutches and possibly the seals.
 
Diff

ok i have an 89 SC auto transmission.....how would you tell if your differential is bad......plus i do not think the fluid has ever been changed...if it is bad......how much would it cost to repair.... plus those i think they are 3.73 gears they sell on ebay?.....would they be worth putting in....what exactly do the gears with different numbers do...and are any tools required and about how long would a project like this take....any and all info would be appreciated.....Thanks for your time....
 
Duane - I don't know what mileage you have on your SC, but a '90 is a pretty sure bet for some clutch plates to be replaced or more packed in to get back to spec. That article is great, but you have to decide whether you are up to the task, including tools. Plus the Mustang has the solid axle versus our independant - by the time you remove the rear plate & hanger to access the gears you might as well remove the pumpkin altogether and work on it on a bench. Also if you are considering lower gears, (3.55 is recommended for the auto & 3.27 for the 5 speed), you might as well take it to a shop & have the whole thing re-built including new side shaft & pinion seals. This is what I ended up doing on my '93 and the labor was lower because I delivered them just the diff. I can't exactly recall what it cost, but I bought all the parts from Summit originally, thinking I was going to do it myself. The gears are about $200, clutch pack $60 & say another $40 for all the seals & bearings. Overall say $500 incl. labor
 
how do you know?

Spin the tires and see if you have 2 marks the same length.If one is considerably longer or maybe you only have 1,guess what?It's clutch time.
 
Joisey Jim

Thanks for the tip. I’m doing a lot of maintenance on my SC this summer, so I’m trying to save a little $$. But… I have been thinking about the special tools required and trouble I might run into. I might just call around and see what they will charge me if I take out the diff and have them rebuild it. I think I will stay with the gears I have right now. Everything else is stock, so why start changing gears?? I also need to replace one of my inner CVU boots, so I thought I might as well change them all. And… while I’m there, I thought I would change the wheel bearings. Its all starting to add up.

Does anyone know where I can get reasonably priced CVU boots and wheel bearings??

My SC has about 115,000 miles on it. Transmission=7,000 miles. Engine=3,000 miles.

Thanks,
Duane
 
Duane - if you are not changing gears, it doesn't leak and the "kirby" test above doesn't reveal worn clutch plates; then I'd just change the oil. I don't know about the CV boots for the rear axle - you'll have to call around to the auto parts shops. Front drive boots are easy to find, but you might end up at Ford for those or check out the replacement axle companies, like the ones on our "links" as well as the TCCOA. Good luck.
Jim.
 
When one tire spins (such as Garys) ..Then you know its time..Also to a lesser extent..If you are running street tires and both tires spin..Check to see if one line is darker then teh other..Thats a good indicationsomethings up...With good tires youd be a one legger as well
 
I think I will do that rubber to the pavement test. If it looks good, I will just change the oil. Since Im taking off my CVUs, I think I will change those seals. That should be simple. Right??
 
Gary,

I already ordered a rebuild kit from Ford. I can't decide whether to leave the 3.27s in or not. If you get used to the 2nd gear rolling stops, you'd know what I mean.

Anyway...I'm more concerned about acquiring your "other" mod. ;)
 
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