Trak lock question

[MikeG]

Thinking of rebuilding the clutch packs in an 8.8 diff..... some random thoughts, after reading the procedure here:

Rebuilding A Traction-Lok Differential

www.therangerstation.com

My truck is a 97, and somewhere around 300K miles, so best guess is the clutches are beyond worn out.

Looking at the pictures, it seems that:

1. Pinon drives the ring gear
2. Ring gear drives the case
3. Case drives the friction plates
4. Friction plates drive the steel reactor plates (terms from the referenced link).
5. Steel reactor plates drive the side gear
6. Side gear drives the axle shaft(s). Side gear closest to the ring gear drives the left axleshaft, and other side gear drives the right axleshaft, through the spider gears.

Correct?

So.... theoretical question..... if the clutches / reactor plates were WAY past worn out.... would it be possible for the diff to spin, but the axle shafts to not move at all????? Seems absurd, but the mechanical link between the axleshafts, and the pinion, seems to be the clutch pack assembly.

Or am I missing something?

 

[Dirtman]

The clutch packs/springs simply provide force against the side gears to help them spin together, when worn out the axle just behaves the same as an open differential.

 

[Curious Hound]

Thinking of rebuilding the clutch packs in an 8.8 diff..... some random thoughts, after reading the procedure here:

Rebuilding A Traction-Lok Differential

www.therangerstation.com

My truck is a 97, and somewhere around 300K miles, so best guess is the clutches are beyond worn out.

Looking at the pictures, it seems that:

1. Pinon drives the ring gear
2. Ring gear drives the case
3. Case drives the friction plates
4. Friction plates drive the steel reactor plates (terms from the referenced link).
5. Steel reactor plates drive the side gear
6. Side gear drives the axle shaft(s). Side gear closest to the ring gear drives the left axleshaft, and other side gear drives the right axleshaft, through the spider gears.

Correct?

So.... theoretical question..... if the clutches / reactor plates were WAY past worn out.... would it be possible for the diff to spin, but the axle shafts to not move at all????? Seems absurd, but the mechanical link between the axleshafts, and the pinion, seems to be the clutch pack assembly.

Or am I missing something?

You missed the cross pin. The carrier (case) drives the cross pin with the spider gears. They, in turn, drive the side gears and axle shafts. The fact that the spider gears can rotate independently on the cross pin, is what allows the differential action. The spring and friction plates/reactor plates just add friction and force to try to make the side gears and axle shafts spin together.

 

[pjtoledo]

you're forgetting the the case drives the pin which drives the spider gears, which drive the side gears, which drives the axles.
in a straight line the friction parts are just going along for the ride.

when one wheel is spinning, the friction parts are actually trying to stop /slow down that wheel.


Eric seems to have beat me to the punch.

 

[Curious Hound]

Eric seems to have beat me to the punch.

Sorry?

 

[pjtoledo]

I was distracted looking at an opossum in the back yard monitor. retirement is so much fun.

 

[Dirtman]

I was distracted looking at an opossum in the back yard monitor. retirement is so much fun.

Thats hot...

 

[MikeG]

Yeah thought about the cross pin / spider gears later. Anyway..... so are the axle splines still engaging the side gears, in a trak lock rear end? I can't tell looking at the pictures from the rebuild article.

 

[Curious Hound]

Yes. That is how it transmits torque to the axles.

 

[MikeG]

Alright I looked at the article again and now I think I get it. With the clutch packs between the case and the side gear, they're just adding drag if one of the side gears isn't turning as fast as the case, or close to it.

Anyway what prompted the question was doing some digging about the relative strengths of the 7.5 and 8.8 28-spline rear ends. There are a number of threads on the mustang forums where guys swear that an open 7.5 diff is significantly weaker than a trak-lock 7.5 diff. Apparently, when those let go from too much horsepower/torque, the side/spider gears break (if I'm reading those threads correctly). So, unless the side/spider gears are different between an open and a trak-lock case, then I don't know why this would be true.

I definitely get that replacing the entire case could yield more strength, because then it is as strong as whatever locker or spool is put in, vs. the usual diff design. But, if it is true that a trak-lock diff is stronger than an open diff, there must be some difference in the parts. At least I would think so.

 

[MikeG]

So no opinions / experience as to whether a trak-lock carrier is stronger than an open carrier?

 

[PetroleumJunkie412]

8.8

You will not regret it.

 

[Dirtman]

So no opinions / experience as to whether a trak-lock carrier is stronger than an open carrier?

I can't see how it would be or even matter, the weak link on the 7.5 is the pinion.

 

[Curious Hound]

I doubt there's much difference in the strength of the carrier. If you want a little more assurance, get a 31 spline 8.8.

 

[MikeG]

Oh I'm not worried about it for my truck. Already has 8.8, and survived a lot more abuse than the factory would have recommended it for, believe me. Was just curious why the mustang guys thought the 7.5 trak-lock was so much better than the open 7.5 diff. Didn't make sense to me when I read that on their forums, thought maybe there was some logical reason. Figured you guys would know.

Maybe all just imaginary.....