LS in dentsides

[LEB Ben]

Can someone help with some info on the limited slip set up in dentside axles? I'm not confident enough in doing my own gearing work, so I've only cracked open diff a few times. First I'm assuming the LS is a torque sensitive setup as opposed to a speed sensitive setup right? Secondly, at what torque rating does it take before the LS actuates before engaging (ie how much slip does it allow before engaging)?

 

[TexasNomad]

I know of some dvds on how to rebuild/Install and just do general work on 9inchs..

 

[LEB Ben]

Thanks Tex...I think I'm capable to do the work...I just want it to be on someone else's head if something goes wrong...haha. And I was more wondering on the D60 LS units, I was wondering what the torque rating was before the clutch engaged (if it's a torque sensitive unit).

 

[Skandocious]

As far as I know-- the point at which the LS locks up is dictating by how much friction modifier you've got in the fluid. The correct mixture of oil and FM will allow the tires to spin at separate speeds when making tight turns (one wheel turns SLIGHTLY slower than the other), but anything beyond that will lock it up.

My understanding is that friction modifier allows the LS to slip for the tight turns. Not enough FM and you'll get clicks and squeals when turning (cuz it's trying to lock up and it's binding). Too much FM and the clutches will always slip and therefore the tires will never lock up.

 

[LEB Ben]

Thanks Chris...never really understood LS setups, I get open diffs and lockers, but fuzzy on LS's. So basically what you're saying is the 'torque rating' I was referring to is pretty much based on the amount of FM...and I'm assuming this holds true between torque and speed sensitive LS's?

 

[Skandocious]

I've never heard of torque or speed sensitive LS... My understanding is that it's strictly based on a DIFFERENCE in speed between the axle shafts. The mechanism that allows it to do this-- I have no idea, lol.

 

[blackhat620]

Ben,

Here are some links to basic differential & locker types and how they work. The Ford Trac Loc is a clutch type LS. It is a fairly weak unit and they do not work very well, nor do the clutches last very long, especially if you haul heavy loads or tow alot. The max transfer of torque between the wheels is about 2.5:1. The more FM added the easier the clutches slip so the less effective the LS is. The trick is to add the least amount of FM necessary to eleminate chatter (noise).

If you have a Ford Trac Loc and want to rebuild it fine, if you do not have a Trac Loc then you are better off purchasing an A/M LS (ie truetrac) or full locker, do not waste your money purchasing a Ford Trac Loc, they are overprice crap.

http://auto.howstuffworks.com/differential.htm

http://images.google.com/imgres?img...um=10&um=1&hl=en&rls=com.microsoft:en-US&sa=X

www.offroaders.com/tech/limited-slip-lockers-differentials.htm

 

[Skandocious]

Well I can't argue about how long the clutch packs last in the stock units (cuz I really dont have enough long-term experience with them)-- but I will say that I used mine in the snow yesterday and it worked wonderfully. I spun the rear tires and Rick (behind me) said they were locked together-- solid as a rock. I was very pleased with the amount of traction I had.

That being said-- if I had a choice when I got this LS, I probably would have gone with an aftermarket LS. I have heard that the other designs are better.

 

[blackhat620]

Well I can't argue about how long the clutch packs last in the stock units (cuz I really dont have enough long-term experience with them)-- but I will say that I used mine in the snow yesterday and it worked wonderfully. I spun the rear tires and Rick (behind me) said they were locked together-- solid as a rock. I was very pleased with the amount of traction I had.

That being said-- if I had a choice when I got this LS, I probably would have gone with an aftermarket LS. I have heard that the other designs are better.

Just and FYI on differentials and LS units. If both wheels have approximately equal traction on whatever surface they are on, then both wheels will turn together with an open diff even on ice. All a LS unit does is help send more torque to the wheel with more traction if there is a different amount of traction between each wheel on the axle. The clutch packs in the Trac Loc LS system just provide resistance to prevent all the power from being sent to the wheel with low traction. Problem with clutch type LS units is the components are always wearing away even on dry pavement. When you haul loads or tow the wear rate on the clutch packs increases rapidly and the units need to be rebuilt in short order. The best option for an LS unit that is not effected by loads or have clutches to wear out are the TrueTrac (Torsen style) gear LS units.

 

[TexasNomad]

Awesome info BH, whats big the difference in Torsen style one?
And also, why is running a locker so bad?

 

[blackhat620]

Awesome info BH, whats big the difference in Torsen style one?
And also, why is running a locker so bad?

I am including some more links with additional information on the Torsen and also TrueTrac (Gear type). Note both the TrueTrac & Torsen LS units are torque sensitive gear units and are similar in operation. The Torsen units are a newer design than the TrueTrac, and there are different model choices depending on the application.

FYI most all LS units are "Torque Sensing", whereas Lockers (ie Detroit) are "Speed Sensitive". (There are some "Speed Sensitive" LS units but they are not very effective and are in limited use).

http://en.wikipedia.org/wiki/Torsen
http://en.wikipedia.org/wiki/Limited_slip_differential
www.torsen.com/general/general_faq.htm
www.torsen.com/files/Traction_Control_Article.pdf
www.4crawler.com/4x4/TrueTrac.shtml
www.4xreview.com/Reviews/ProductReviews/Drivetrain/TractechTrueTrac/tabid/313/Default.aspx


There is nothing wrong with running an "Automatic Locker" (ie Detroit), depending on the use of the vehicle, but understand that all types of differentials (open, LS, Auto Locker) have there strengths and weaknesses depending on the application.

For a daily driver and Auto Locker is noisy and imparts increased stresses on the axles and driveshaft. The advantage of a locker is that both wheels will be locked together on an axle even if one wheel is in the air. An auto locker is a great disadvantage on the street in slick conditions as it can cause unpredictable handling do to the automatic nature of locking and unlocking. Auto lockers are not used in front axles on the street do to steering difficulties. Also lockers are more difficult the shorter the wheelbase of street vehicles. Auto lockers should not be used when towing or hauling heavy loads on the street as it can cause broken axles, drivelines etc.

An LS unit has much better road manners than an Auto Locker, and the Gear type LS units are almost as good as a locker for the normal user. Note lockers are needed for rock crawlers.

The best of both worlds is a "Selectable Locker" (ARB Air Locker etc) as they are normally an Open Diff until the switch is thrown by the driver Locking both wheels together on the same axle. Note "Selectable Lockers" are switched off to turn etc. When a selectable locker is locked it is just like a spool.

For front axles either an LS or Selectable locker is your best choice, Automatic lockers are a bad choice in a street driven vehicle.

 

[TexasNomad]

Awesome! thank you

 

[LEB Ben]

Thanks for all the info Greg...I was just curious because I have one for a rear D60, and Chris' mention of his in his wheeling thread got me thinking about it, and figured I better start gathering info for when the Bronco gets upgraded. Gonna rep ya when I can.

 

[blackhat620]

Ben,

If it was me and i was going to upgrade the D60 for the Bronco, i would look at selling the factory LS unit, and then save your money to get an ARB Air Locker. If the Air Locker is out of your budget, then a TrueTrac LS would be in order, but i would highly recommend the Air Locker especially in the short WB Bronco. Once you have a selectable locker nothing else compares.

 

[LEB Ben]

Good call Greg...you've definitely cleared alot of stuff up for me...I realized LS was inferior to a locker, just didn't realize how inferior. But yes, a selectable locker is definitely for me. I just thought it would be cool to keep some Ford Heritage in this rig...but looks like traction isn't the place to be sentimental. However, Since this is still a street driven rig occassionally (more often than I'd like right now)...what are your feelings on doing a rear locker and a Ford LS up front...or should I go the aftermarket route for a front LS too?

 

[blackhat620]

Good call Greg...you've definitely cleared alot of stuff up for me...I realized LS was inferior to a locker, just didn't realize how inferior. But yes, a selectable locker is definitely for me. I just thought it would be cool to keep some Ford Heritage in this rig...but looks like traction isn't the place to be sentimental. However, Since this is still a street driven rig occassionally (more often than I'd like right now)...what are your feelings on doing a rear locker and a Ford LS up front...or should I go the aftermarket route for a front LS too?

Yes being sentimental is a bad route when it comes to inferior parts.

Since your rig is primarily a DD, If you can only afford 1 selectable locker, then i would put the "selectable locker" in the front axle and either an A/M LS or leave the rear open, if funds are tight (who's isn't). Front diffs are easiest to control (ie steering etc) if they are open, so a selectable locker in the front is the best choice. An LS in the front can give tricky steering on ice coverd roads, and is not the best choice for a DD. IMHO, i would save and put a selectable locker in the Front axle first, then save your money and put a selectable locker in the rear at a later time. I personally would not spend the time & money putting the FMC LS or an A/M LS in the rear, unless you are just dieing to do the job twice. Once you have a selectable locker you will not want anything else.

 

[TexasNomad]

Yes being sentimental is a bad route when it comes to inferior parts..

That's what I tell him about his GPs

 

[LEB Ben]

Again Greg...thanks for the input. I just didn't know if a LS front would help with streetability...but once I get the '96 back in my possession, that will be the DD, and the Bronco will be relegated to 'fun duty' once again. So f/r selectable lockers it is...got a lead on a rear sterling 10.5...so I'll probably go that route, now that I think about it...and there's a guy I know with several '79 HPD60's...and that'll probably go up front. So much to do...so little time....and money. I'm one of those guys that likes to do it all at once, so this probably won't happen til the summer...just gaining ideas and expertise in the mean time. So thanks again for all the valuable input.

That's what I tell him about his GPs

I'll refer you to post #165 in this thread:

http://www.fordtruckfanatics.com/forum/showthread.php?t=10648&page=17


SOOOOOOOOOOO...bite me Tex...haha.

 

[SuperCab]

That's what I tell him about his GPs

Reps to you. You are a smart man...

 

[TexasNomad]

Reps to you. You are a smart man...

Hey! watch who your calling smart