A "posi" is short for posi-trac, which is what some manufacturers refer to when talking about their limited-slip-differential (LSD). A limited slip differential is a traction-aiding device. Basically, if one tire begins to spin faster than the other, power will be transfered to the slower moving tire so traction can be gained. However, there is no complete "lockup" and one tire will likely continue to spin faster than the other. The LSD allows "limited slip" from side to side, hence the name.

A locker can best be described as a "no-slip" differential. Once one tire begins to spin faster than the other, the locker will "lock" the axles together for a perfect 50/50 split from left to right. Because of this solid lock, lockers can be somewhat annoying on a street-driven vehicle. Lockers are typically used in extreme off-road conditions (such as competition mud racing, or extreme rock-crawling).

There are many different types of lockers and LSD's. For your application, a factory or aftermarket LSD would probably be a nice improvement over a stock "open" differential. An open differential offers no traction-aid in the event that one tire begins to slip. Power is not redirected to the other tire. Your truck may or may not have a factory LSD already in place.

Hope this has been somewhat helpful. If not, ask again/wwwthreads_images/icons/smile.gif/wwwthreads_images/icons/wink.gif.

TEX

/wwwthreads_images/icons/wink.gif Got Mud?
G.U.M.B.O. Mud Racing

 

Thank you very much for the detailed explanation. I even understood every word /wwwthreads_images/icons/tongue.gif

So I guess the next question would be -- How would I be able to tell if this was something I already had? My truck is a 77 Chevy 1/2.

Thanks again!

/wwwthreads_images/icons/blush.gif weehaa!

 

First of all, asking even a simple question, doesn't show ignorance, it shows intelligence. /wwwthreads_images/icons/smile.gif I'm not sure if you've heard this before, but: "The only dumb question is one that isn't asked".

Does this truck have the original axles and such? I could be wrong, but to the best of my knowledge, these vehicles had a build sheet somewhere in them, a plastic sticker with options listed on them. In some vehicles, a common place is in the glove box. I can basically guarantee you don't have a locker, or you'd probably have took it to a mechanic complaining of problems with the rear end. If you find a build sheet and see "Locking differential" listed on there, it'll be a Gov-lock, which is more like a limited slip than a locker. I'm not too familiar with the insides of differentials, so I'm not totally sure how to tell whether you have a locker or LSD. /wwwthreads_images/icons/smile.gif/wwwthreads_images/icons/wink.gif/wwwthreads_images/icons/cool.gif Someone let us know!!!

Tim
"The_Sandman_454"
/wwwthreads_images/icons/cool.gif '79 Suburban 4x4 454, 6" lift, 35x12.5s & '85 GMC S15 4x4

 

Thanks for the encouragement. I'm TRYING to learn stuff.

Anyhoo, about the truck... the answer to that question would be - don't know, but I would imagine that it is original because from what I have learned about the guy I bought it from, well, let's put it this way... there isn't enough duct tape in the world... /wwwthreads_images/icons/smile.gif

Cheryle

/wwwthreads_images/icons/blush.gif weehaa!

 

Hey, if it can't be fixed with duct tape, WD-40 and zip-ties, then it isn't worth the effort!!! /wwwthreads_images/icons/wink.gif/wwwthreads_images/icons/smile.gif
Sorry, just had to butt in there...

- J.R. -

 

Hey, don't forget about bailin' wire & bungee cords. And the Zip ties are great - I have a friend using one for a fan belt (NO SH**!). BTW, duct tape is also affectionately know as "silver weld" or "1,000 mile-an-hour tape" - depending on who you talk to./wwwthreads_images/icons/wink.gif

TEX

/wwwthreads_images/icons/wink.gif Got Mud?
G.U.M.B.O. Mud Racing

 

I 've got a 77 GMC 1/2 ton it has a 12 bolt in it, Good Luck White Knight CLRR

 

I thought the "100 mph tape" was the premium brand duct tape? /wwwthreads_images/icons/wink.gif.
Awww, whatever. As long as it all works!

And to think you can spend several hundred dollars in replacement belts and/or those special link belts when you can just use zip ties!!! /wwwthreads_images/icons/cool.gif

- J.R. -

 

Jack the truck up so that both rear tires are off the ground. Then turn one of the wheels forward. If you have an open differential one tire will turn the opposite way. If you have some type of locking differential both tires will turn forward.

Don't forget the bailing wire or coat hanger and the vise grips!!! Heck I think all of these items should be included when you buy a used truck!



Greyghost
77 Jimmy

 

Just wanted to jump back in and defend my duct tape comment...

I'm all for McGyvering when necessary, in fact, I believe you can NEVER have too many zip ties. I currently have a bungee cord holding in my battery and have been known to use vise grips as an antennae, but nearly everything that has been replaced on my truck has had some sort of tape on it. Maybe I'm wrong, but I see tape as a temporary solution....

Ok, I'm done now/wwwthreads_images/icons/smile.gif

Cheryle

/wwwthreads_images/icons/blush.gif weehaa!

 

I would agree with you only if you take the "temporary" duct tape and replace it with zip ties or the vise grips you mentioned previously for a more permanent fix! /wwwthreads_images/icons/wink.gif/wwwthreads_images/icons/smile.gif

Seriously, though, I know it hurts to buy someone's else's vehicle in that condition. It's not YOUR duct tape...

I'm sure you'll get your truck exactly the way you want it!

- J.R. -

 

I use duct tape to seal my roof on My 79 K5...New strip every 2 months, black to match the body color. LOL
About your bungee corded battery. Get that thing properly bolted down. The acid (fumes also) from the battery will ruin the bungee in short time. Also, if off roading a bungee wrapped around a 30lb battery is just not safe. The battery will come loose and if your lucky only take out the radiator.
Be sure the battery tray is in good condition and not weakend from rust/
Factory battery trays are still available from the dealer. I think I paid like $17 this spring for my 75.

Grim-Reaper

 

Yeah, I have to go with Grim on this one. As one who sanctions mud races, we won't allow bungee-battery-tie-downs & for the very reasons he mentions. My factory tray was mostly missing, so I got a tray & top at Wal*Mart for next to nothing. The tray is bolted to the truck & the metal top is held down by bolts as well. I feel much safer about that.

TEX

/wwwthreads_images/icons/wink.gif Got Mud?
G.U.M.B.O. Mud Racing

 

Gotcha. I guess I'll have to move that item further up on my list and remove the entry for "get extra bungee cords." hee hee hee

Thanks for everything! You guys are "da bomb".

Cheryle

/wwwthreads_images/icons/blush.gif weehaa!