Adding extra clutches to a Dana 80 Trac-Lok

[tarussell]

On an earlier post the discussion of re-stacking the order of the clutches was brought up. I responded, but I wasn't real clear on what I had done and I thought I would do a better job at describing what I had done here. I know this is not earth shattering news but I thought it might help someone looking for better traction and not wanting a true locker.



On the Dana model 80 Trac-Lok the factory clutch and friction plate order is :

dished disc ( preload ) on the side gear

( 1 ) clutch disc

( 1 ) friction plate

( 1 ) clutch disc

( 1 ) friction plate

( 3 ) clutch disc's in a row

( 5 ) friction plates in a row

This allows for an aweful lot of slipping. When I re-stacked my Trac-Lok I changed the order and added more surface area by adding another clutch disc and taking away a friction plate.

New stack order is as follow's

Same dished disc on the side gear for pre-load

Start with a friction plate

then use a clutch disc

and alternate the plates and disc's for a total of twelve ( six of each ) ending with a clutch disc.



Now in order to do this you must get an extra clutch disc ( I had an extra clutch pack re-build kit for another Dana 80 ).

My whole point for doing this was to make the Trac-Lok more durable and add a little more grip ; what I got was a lot more grip and I believe it is very durable and should last a whole lot longer than the factory stack order. On a tight turn under power the inside tire will chirp and sqwuak and bite the whole time, but it is not so bad that it is bothersome.

The moral of this is if you want more grip from the Trac-Lok just re-stack the order of the pack and leave out a friction plate and add a clutch disc. MAJOR improvement in the traction department with out going to far. Hope this helps, Thomas

 

[rspinks]

That is great info, I hate my loose factory LSD. The factory arrangement is very surprising to me, I'd like to know why they would have 5/7 regardless of stack order. I may have it backward but assume the plates are the ones fixed to the diff case and the disks are splined to the side gear. The overall clutch "pack" is simply transferring torque from the side gear to the case, so wouldn't you want the same number of disks and plates? I'm picturing the factory clutch pack being more connected to the side gear than the diff case.



Rich

 

[Proram]

LSD

Is This something i can handle? i have all the major tool with the exception of a spreader. Do i need a Spreader? also do you have the pn# for the clutch pack kit? TIA Proram

 

[jstarnes]

if your not carefull

you might cause the case to distort(but only when the bolts are tightened )I have seen this happen a guy tried to add 1 warn out disk to the pack and it caused a problem when he tried to set up the gears (to much backlash in one area to little in another )I have thought of taking the case haves to a machinist and having him Knurl the seat area to have a kinda controlled increase in pressure?

just a thought

Jason

 

[tarussell]

Rich- To the best of my knowledge the majority of the people complain about the noises and clunk of a tight L/S , so they take steps to make the clutches a little more user friendly and help them slip. that's why the stack order is all goofy from the factory ( Ford Dana 80's and Dodge Dana 80's are stacked the same way) .

I believe the way I stacked the pack is the way it was supposed to be in the first place ; but to many people don't like to feel the tires chirp and groan so they soften up the diff by restacking the disc's.

And yes the friction plates are the ones that are notched for the case and the clutch disc's are splinned to the side gear.



Pro Ram - Yes you do need a case spreader to get the diff out, but that is the only special tool required. All the rest of it is very simple and basic. I will look for the Spicer part # for the clutch pack rebuild kit and post it for Ya' .



Jason - There should not be any need for machining the case halves because a friction plate is being eliminated and a clutch disc is taking its place. According to my micrometer the plates and disc's are yery close in thickness and should not make much difference on the belvel ( sp ) spring for pressure. If the clutch is a little thicker it should only increase the preload pressure a very small amount and not cause the case halves to distort at all . I measured the packs before and after and all is well with the space between the two halves of the case. I thought about shimming it up real tight but there is no need with the new stack order and the propper amount of plates and disc's.



Thomas

 

[parcher]

Before you split the diff make sure you mark it to make sure it stays properly indexed. The case halves are bolted together at the factory then machined, if you mis-index the case you will have run-out. Jason, I beleive this is what happened to the case you mentioned.

 

[Roger rodbolt]

Thomas,

I restacked and added the plate as you did about 2000 miles ago (after I demolished all the spider gears and two of the cross pins) on my factory Dana 80. I'm running it with no LS lube and am getting a ratcheting and popping noise on tight turns. I'm runnig large BFG AT's but never get tire chirp. I'm using Amsoil 2000 75-90 gear lube. Can you "feel" the LS popping on turns? I actually think that I have other problems in the differetial but have not taken the time to tear into it. Larry

 

[tarussell]

Parcher- Good point on the run out concern; I even marked the cross shaft to get them back into the same groves. I don't know if it makes a difference on the shaft but it can't hurt to be to careful.



Larry- I can feel the clutches slip but mostly the tires chirp when the bed is empty. I only have the 265/75/R 16's on the truck right now so that might be the difference. Your larger contact of a bigger tire and any additional weight may cause your clutches to slip and not skip a tire.

One question though, did your case halves look good when you broke the original spider gears? Did the trust washers look good and there mating surface along the case ? And finally is the grove where the cross shaft rides still tight and look good ? The reason that I ask is becuase the side gears are held in place by the four small pinion gears on the cross shaft and if they have to much play in them than all hell could be breaking loose with your clutches and plates. Let me know, I am currious to see what is wrong.



Thomas

 

[Roger rodbolt]

Thomas,

Everything looked good because I bought a used carrier for less then I could purchase the broken spiders, etc. I probably should have checked thing better but there was no wear on the clutches and the cases looked perfect. Someone mentioned aligning the case have properly and I alway mark them before disassembly so that is not an issue. This rear ratchets like a locker, sorta of strange... ... ..... I guess that I should purchase the parts for the original carrier so I'd be ready to swap this one out. Thanks for the interest and help . Larry

 

[Gary - K7GLD]

HMMmmm - wonder if there is a "test standard" to determine proper LS operation? Seems like most fellas fly by the seat of their pants in determining LS action - and "adjust" with the recommended additive...



My own LS will easily break loose on the inside tire in loose surfaces, and will chirp the inside tire on pavement on a tight turn if I drive over any irregularities that contribute slightly to lessened traction - I assumed that was normal and about right for proper operation...



Seems I have read mention about raising one wheel, and applying a specified amount of torque to it to see how much effort it required to make it turn?

 

[tarussell]

Gary - I think there is a "test standard" for a propper working L/S. For the life of me I can't find my old Spicer Manual that has that info. But here is what I did. Since when I changed my Clutch pack the truck was new I figured the L/S was in good working order ( it seemed to be O. K. I just wanted to arrange the disc's and plates for more durability ) I jacked up one side and used an old railroad stick to see what it took to move one side . I know this is kind of caveman technology but it somewhat proved to me that what I did had a positive effect on the friction of the pack.

After I re-stacked the pack I tried the railroad stick again and it tried to move the opposite tire; I could barely get any movement from the free side. I don't have a continous torque value like the book say's but it did increase resistance so I figured that it was successful.



If anyone has a Spicer rating on what the continous torque reading should be to test the L/S PLEASE post it. I will continue to look, but if someone beats me to it -let us know.



Larry- Let me know if you need the spiders and cross shaft; I got some Ford Dana 80 take out diff's for spare parts. They are all 35 spline side gears just like our's.



Thomas

 

[Roger rodbolt]

Originally posted by tarussell



Larry- Let me know if you need the spiders and cross shaft; I got some Ford Dana 80 take out diff's for spare parts. They are all 35 spline side gears just like our's.



Thomas

Thanks Thomas, I'm sending a PM. Larry

 

[tarussell]

Larry - I sent you a PM on the parts. I also just found the phone # for the shop w/ the spool info; I'll PM Ya' later w/ what to do .

Thomas

 

[Gary - K7GLD]

The reason I mention a test standard for LS operation, is that simply upping the internal clutches to get more apparent action MIGHT exceed what the rest of the differential is designed to handle reliably - much like bombing our Cummins to 1000 HP - good power, but sorta hard on longevity!



A "loose" LS isn't of much practical value - but does no damage - a "tight" one will give good traction - but maybe only for a little while!



All depends on personal use and expectations I guess...

 

[tarussell]

I thought about that too, and did not want to go to far. Since I did not test the break away torque I don't know if I exceeded the design limit or not. It seems logical that the original engineering may have stacked the clutches and plates this way. I was told that some of the auto manufactures request a " softer " L/S to avoid excessive clutch chatter but durable enough to live in a heavy truck. I assume that that is true.

I did some looking on how some other L/S's made by Spicer were set up and they ( older designs ) had the clutches and plates stacked in alternating order too. So I figured that I would change the packs to how they should have been stacked( in my opinion ). Only time will tell if I was right,but so far w/24,000 miles everything look's and feels great. As with anything there must be a trade off, but hopefully I extended clutch life by adding friction surface and did not shorten the pinion and side gear life by over loading them.

My original L/S set up worked as designed but I wanted to step up what it took to break one side loose from the other w/o increasing the preload pressure. Hopefully there is an appropriate amount of overbuild in the internals to handle the added traction... .

I know there is a limit to what can be done-hopefully I have not crossed it yet. Thomas

 

[Gary - K7GLD]

Do you still use the "standard " amount of LS additive with your setup?



And maybe I missed it, but what differential lube are you using?

 

[tarussell]

Gary - No additive at all . Valvoline Synthetic 90 weight. I don't tow that much so I don't run 140 weight.



I was going to use the " standard " amount of additive but it seems to have very good manners on the road so I did not add any. The clutches seemed fine with no unusual wear on them after 11,000 miles. I will be checking everything out again this spring so I will get another peak at how everything is doing; but so far all is well and I am getting confident that it is going to stay that way.



What are your thoughts on the additive ???



Thomas

 

[Gary - K7GLD]

Well golly - if it's behaving fine without any additive, no apparent need to add any...



I'm getting ready to drain/refill my differential - I have the Amsoil 75/140 stuff - really doesn't seem all that heavier than their 80/90 wt stuff I also got to put in my 6-speed... Be interesting to see if there's any noticeable operating characteristics...

 

[tarussell]

Proram-- part #'s

Proram -- I found the part #'s for the clutch packs.

Spicer #'s for inner diff parts on a Trac-Lok # 708051 kit

47800 - thrust washer - pinion T/L

47796 - diff. side gear T/L

47798 - pinion gear T/L

47802 - cross shaft T/L

702009 - pkg:disc & plate T/L



Now these are for my B. O. M. # I assume these #'s will work for you. My B. O. M. # is " 606710-4 " for the Dana 80.





I hope this helps, Thomas



Larry - I sent Ya' a PM , the parts are on the way .

 

[fox]

Let me jump in here real quick. This topic ONLY covers the 3500 trucks, if I read the manual correctly. The 2500 looks - in the manual - to be alternated completely.

Also , it would be nice to know what DANA has to say!