Putting LSD in a Dana 70 with 3.07's

[Brian R]

This is my first post to this forum. I think I read somewhere on this site that 3. 54's were the tallest gears available in these trucks. My differential tags both say 3. 07 and it sure seems (no tach) like 3. 07's on the highway. The truck is nice and quiet on the freeway. I would like to put in an LSD but with a couple of phone calls It seems that there is not one available for the carrier used by the 3. 07 axle. By the way, did some of these come with Dana 60's in the back or is mine for sure a 70? I think it's 70 in the back with a 60 in the front but I don't know how to tell by looking.

 

[Brian R]

I do not think my signature showed up so I am going to try again.

 

[Paul Herioux]

Yes your rear axle is a Dana 70 with 3. 07 gears. I believe the LSD carrier was an option that started in the 91 trucks but I'm not sure on that. The Dana 70 uses the same carrier from 2. 90 to 4. 56 ratios so finding an LSD for one shouldn't be to much of a problem. I have on out of a 92(?) on the shelf in the garage that needs a rebuild when I find the time to do it. I still have to decide what I'm going to change the gears to. With the O/D and the taller tires I don't need the 3. 07's anymore.

 

[Brian R]

Would you be interested in selling that unit?

 

[Paul Herioux]

Sorry but no. It's set aside for my rig. Just need the time and money to do it.

 

[Lars]

I have the same setup in my rig, W250 Dana 70 w/3. 07s and automatic. Not sure of the brand but I bought and had someone else install a posi in the rearend. $1000-ish total.



Paul, tell us more about your 47rh transmission. New? Used? Cost? Did you do the work yourself? Thanks, Lars

 

[RDusch]

Brian,



You might want to consider a LOC RITE locker for the rear, they cost around $350 and work quit well, i've got over 60k on mine with no problems, they can be installed in less than an hour.



Rick

 

[cummins2go]

3;07 gears

Hi Brian the carriers are the same for 3:07 to 4:10 on the 3:07 the dana 70 housing is actually different from the standard dana 70 but the carriers are the same so you shouldn't have any problem finding a posi I have never seen a dana 60 put behind a cummins in the rear end Here is a place that is real helpful when it come to differentials http://www.4x4now.com/4wsdtrr.htm Reider racing I hope this helps

Darrin

 

[Paul Herioux]

Lars,

Search the first gen forum for "47rh" for the past year. I've posted 3 or 4 times with instructions and updates. I'm getting to the point now where I have to look at my own posts to remember what I did. Only thing I haven't been able to post are the pictures I took with the digital camera at work. I need some better software so I can trim them down to a reasonable file size.

Just ask the guys I've e-mailed them to. :--)

 

[ScottB]

I have a limited slip unit I would be interested in selling just let me know.

 

[Phil May]

Go with a Detroit Locker mine has lasted 100,000 mile so far under extreme punishment. I think it cost $800 installed. Just be carefull decellerating when its slippery, they lock up both directions. I have not had any driveability problems like everyone said I would. The only drawback is tire wear. Once the tires start to get wore down big chunks come out of them.

 

[Brian R]

Hey, ScottB: I'm not sure how to do this but what kind of LSD unit do you have and how much do you want for it?



Brian Roth

broth@sanjuan. edu

 

[TLowery]

I would second the recommendation to use a Detroit Locker. For dependability, function, longevity they are impossible to beat. I run Detroits front and rear in my Jeep and I am planning on putting one in the rear of my truck. The traction given by a limited slip (posi) does not compare to the traction given by a real locker.

 

[Brian R]

Can you describe the difference mechanically? My understanding of an LSD is that a clutch pack limits the movement in the spider gears. How does a locker work?

 

[Phil May]

I am not 100% sure because I have never had to fix mine yet. But I think the spider gears are shaped like a cam lob that when there is a difference in wheel speed forces it to "Lock Up". They lock in both directions. I had a LSD that went bad before I put the Locker in, No comparision in performance. The Locker is 100% better in all situations.

 

[TLowery]

Many limited slips do use clutches to try to control traction. When one tire looses traction the other side will recieve all of the torque just like in an open rear end. Limited slips use clutches, or other means, to try to harness some of that torque and apply it to the side that does have traction. There are several different designs and some are more "positive" than others but none match a true locker as a positive traction aid.



Lockers also have differences in design, but most use some type of spring loaded side plates that interlock to make a positive connection. Lockers will disengage to allow differential action, but only under certain conditions. Say you are making a turn. If you let off of the throttle, removing the torque input to the locker, the locker will be able to break free allowing differential action. Some like the lock-rite will do so with a loud bang and a noticable lurch from the rear end, while Detroit lockers do so more smoothly. If in the middle of your turn you were to nail the throttle, the locker would engage and you would very likely feel a bit of understeer and hear the tires chirp.



Think of them this way, a LS is normally open and tries to "lock" if needed while a locker is normally locked and opens only under certain conditions. There is a huge difference in the amount of traction offered by the two.



For instance, when I am rockcrawling it is very common for one of my front tires to come completely off the ground (sometimes measurable in feet). With a limited slip, even a very positive limited slip, the tire that is in the air will be getting all of the power. No LS made will be able to turn the tire that is on the ground, the difference in load will be too much for the clutches to make up. With a locker up front both tires still recieve torque and the tire that is on the ground is able to contribute to forward progress. This is an extreme example, but it does help to show the differencce between the two.

 

[Brian R]

It sounds like the Loc Rite is a lot cheaper than the Detroit. Are there fundamental differences in the way they function mechanically or last? Where is a good place from which to order a Loc Rite.