How do I tell if my diff is slipping?

[sbelyo]

I think my diff is on it's way out. When I accelerate while making a right hand turn I can feel a shudder or splipping coming from the rear of the car. I t will also slip for a second if I go in a straight line from a stop. The car doest feel as if it has the same traction that it once did.

I spun the rear wheels for a second while someone watched and both tires spun. It wasn't a heavy burn out, just like 2 seconds to see if both tires spun.

There's 125K on this rear with no fluid changes

 

[HOOCBB]

That's how mine started, then as I let it go longer, it turned into a grind that required new spider gears.

 

[wmburns]

100k service interval. Rebuild T-LOK

125K no service. Bad. Recommened service interval is 100k. Most ppl recommend sooner.

Your diff is most likely OK (other than old oil). What is going out are the limited slip clutch packs (T-LOK). For what it is worth, it is easier to rebuild the T-LOK than the entire rear end. Should you attempt to do the job yourself, there are special tools that help. Also, follow the instructions about pre-soaking the clutch packs.

You will need a torque wrench.

There is a test of the T-LOK. It involves measuring the break away turning force. With the transmission in neutral, raise one wheel off the ground. Measure the breakaway torque required to start rotation. It must be at least 27 Nm (20 lb-ft). The initial breakaway torque may be higher than the continuous turning torque.

 

[sbelyo]

To measure the torque, do I put the torque wrench on a lug a lug nut of the raised wheel and attempt to turn the wheel?

 

[wmburns]

Ford special tool 205-022

Ford makes a special tool (205-022). It basically ties two lug nuts together to enable the wheel to be turned without turning the lug nuts.

I would suspect the tool could be fabbed with a flat plate and a bolt welded on.

You could try turning just the lug nuts. If the T-LOK is gone, the wheel will turn long before the lug nuts do.

 

[sbelyo]

I'm going to have the diff rebuilt.

It's about $180.00 in parts to replace the clutch packs with the carbon ones and all the bearings.

I found a shop around the corner from work that has done them before. He said roughly about 4 hours of labor.

Now, since the axles will be out and I need a rear brake job as well I'm going to put the cobra setup on the rear with a fresh set of calipers. My only other decision would be to change the ratio from 3.27 to 3.55

I'm afraid that I'll want that in the future and have to pay twice to get it done.

What do you guys think?

 

[flstang65]

I would go 3.90's or 4.10's.

 

[sbelyo]

I think I'm gonna get new tires instead of changing the ratio. Tirerack had a deal I couldn't pass up and I'm not liking the Nitto NT555's any more.

Ride quality sucks big time after they wear, and two of them have a slow leak with no visable holes or nails. So I think my money is better spent on tires

 

[wmburns]

Ride quality sucks big time after they wear, and two of them have a slow leak with no visable holes or nails. So I think my money is better spent on tires

Check your rims during the tire swap. Look for cracks or other defects in the bead seal or castings that may be the source of the leak.

 

[sbelyo]

Will do....

I'm going to take all 4 rims off this weekend and scrub them down with simple green on both sides. I'll check then. I did find a nail in one of them, so the term visable must be taken lightly Ha ha ha.

Since the Nittos are softer and grip harder my gas mileage took a hit. I hope the BFG KDW's are better

As far as fluid goes, I should use 2 Quarts of 75W140 Full synthetic correct? I intend too use Royal Purple, so no friction modifier is needed right?

 

[HOOCBB]

I think 75-140 is the now correct weight. And yes, Royal Purple already has a friction modifier in it, so you don't need any extra.

Also, if they are completely rebuilding the diff including bearings, why not go ahead and put new gears in it and save the money?

 

[sbelyo]

Yeah, I'm gonna do the gears.

 

[sbelyo]

got 3.55's, new bearings and the carbon clutch pack kit installed. It's nice and tight now with no whine or noise.

I also needed rear breaks and calipers so I had them throw on the cobra rear brake kit and a set of black cobra calipers.