I just got a 1990 Montero (4 door, V6, Manual) as a parts car for my Æ89 Raider. I took the rear differential out of the Montero to rebuild it.

Now, the factory service manual for my Raider shows that the LSD should have one spring plate and one spring disc (as well as two friction plates and two friction discs) per side. But, my differential from the Montero has two spring plates and no spring disks on each side (the spring plates have the lobes on the O.D., whereas the spring discs have the lobes on the I.D.)

So the question is, does my differential have the wrong parts in it, is the Dodge manual wrong, or was there a design change?

Note: The Montero shows 200K on the odometer, yet the all the disks and plates in the differential show very little wear. None of them have more than 0.03 mm of wear (most less than 0.01 mm) out of an maximum allowed wear of 0.10 mm. This makes me think that possibly the differential was rebuilt and the wrong parts were installed.

Any thoughts? Thanks.

I remember Kevin C posting that his LSD had very little wear. If you think about it the LSD is not used. Most people spend 99% of their time on road.

I have no idea about the parts being different. I guess you would need the manual for each year and compare.

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My 89 manual shows the same design you cite. Are there grooves in the housing where the spring plates (ext. lobed) would go? If so, you've got an unlimited slip lsd.

Did you by any chance test the lsd preload before you took it apart?

I have no way to measure the actual preload (as in the pounds of force required to clamp the two halves of the differential carrier together). But, I did make a rough measurement of the torque required to slip the limited slip on both rigs. The one on my original Raider - which doesnÆt seem to lock-up as well as it used to with parking brake application - had a break-out toque of around 75 ft-lbs and a sliding torque of about 50 ft-lbs. The one out of my Montero parts car (which is the one I took apart) had a break-out torque of about 50 ft-lbs and I think the sliding torque was something like 30 ft-lbs.

Thanks for the tip on groves in the carrier housing. It does have some minor groves, but I think I can remove them.

Not wear grooves, I meant machined grooves for the outward sticking lobes on the spring plates - I think they are for torque transfer...

Yes, the carrier has the longitudinal groves machined in it that engage the ears. I'm not sure I quite understand what you are saying, but I'll add this:

As shown in the manual, the differential has a total of 12 slip interfaces (6 per side). In the one I took apart, there are a total of only 8 slip interfaces. Thus, I would expect about 1/3 less torque transfer with this arrangement. (As shown in the manual, the spring DISKS have slip on both sides of them. With spring PLATES in place of the spring disks, there is no slip on any of the faces of the spring plates. However, in both situations, there is slip on the 8 faces of the 4 friction disks.)

I remember a TSB to fix shuddering LSD units that had the tech remove clutch plates. Not sure if it was the V6 or the 4 cyl rear diff.

Also if I remeber right the manual does not match how the rear diff is actually built even before the repair.

Kevin

The running torque should be 70 ft lbs. There are "rebuild" spring plates that are thicker than stock. If you have it apart, replace those. The total rebuild kit is about $650 :-(.

You have inney spring things, and outie spring things, and inney and outie frictions. The outie things index to the case of the lsd and thus to the ring gear. The inney things index to the side gears that the axles spline into. The spring things preload the frictions, so that they bite with less of a torque/speed difference between the axles. When there's a difference in axle speeds the diamond on the pinion shaft wedges the pressure rings outward, loading the frictions and limiting the differential action, sending torque to the least loaded wheel.

Without the outie springs, you are relying only on the outie frictions for side gear torque transfer through the case to the other side gear. I therefore think you need the outie springs.

The 87 shop manual has a much more extensive discussion of the lsd and how it functions, and how ebrake preloading helps, with math and much confusioning.

You measure preload by locking the pinion and one wheel, and twisting the other wheel with a torque wrench. Lower limit is 25ftlbs with old clutches, new is 47-72ftlbs.

For what its worth,
If you look at the parts diagrams for a Starion LSD, and compare it to the Montero LSD parts diagram, you will see 2 different stack-ups........