I have a 81 Rx7 it has drum rear brakes ,
but every time I get on it it leaves 2 equal tire
marks .. but yet I am told that only the disc rear
brake cars have the LSD.. is this true?..
I have never had the rear end apart to look for cluches
so Iam asking .. thanks
Jeff

 

if you've rear drums, it's a safe bet you've an open, not limited slip, differential.

 

When my car had an open diff it would leave two equal tire marks too. And yes, it's true, only rear disc brake cars came with LSD.

 

An 81 Rx-7 CAN leave tire marks? Mine never could with the 12a!

 

Both wheels will drive. The difference is that if one is slipping, say it were on ice, then an open diff applies as much torque as possible without spinning the wheels to each wheel.

A LSD will apply more torque to the non spinning wheel. Its hard to explain so go to the link below.

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

 

are you kidding me?? these cars will spin forever!!! no lie

 

I have drums with a stock rear end it is LSD
Jack the back of the car up and put it in gear.
Try spinning the wheels by hand while someone on the other side holds the wheel if they cannot spin seperately it is lsd

 

Umm.. no.. you leave it OUT of gear... if it's in gear, the tension they'll be feeling is the engine...

--Danny

 

Maybe you got an aftermarket LSD? It could have been installed by the previous owner right?

 

easiest way jack the back up, put it in gear, and try to turn one wheel only, if its turns easy its NOT LSD.

but my 78 has not got LSD, I know because I replaced the diff with a 4.44 ratio from a van recently, yet it will always spin up both wheels in a straight line, even doing burnouts, until I start swinging it around and it drops back to single wheel.

 

To check for an LSD:

put the car up on jack stands, and while in neutral you spin one tire. If the other spins the same way, it's LSD, if it doesn't spin, or it spins the OPPOSITE way, then it's open.

Fun way to check:

Pull the car so one wheel is on your neighbors' front lawn, rev the engine and dump the clutch, check for two tire marks, if you got both, then you're LSD, if you only tore up the lawn, you're open.

Mazda Competition Parts sells a torsen type LSD that David Lane has successfully installed into his 1st gen (it's a GSL-SE, but the case for the diff should be the similar on all models). YMMV of course. The popular option is to take a GSL / GSL-SE rear end and swap the whole darned thing. Search the forum for many how-to's / stories / ect.

HIH/YMMV,
matt

 

the only sure fire way to know you've got an LSD is to remove it and look at it, all the other tests are a good indicator that you have one but are not 100% certain

Guru motorsports in australia make an torsen diff that is specifically for the 1st gen - do a search on guru in this forum and you'll find the link and lots of info

 

if you spin one wheel, and the other one spins the same way, its an LSD, or Posi.... if the other wheel spins the opposite way, its open.

 

I must have an LSD in my car then even though they were never fitted in the UK

the drag from the diff oil can cause an open diff to behave like this too, the only 100% certain way to tell is to take it appart and look

also a worn LSD will act like an open diff

P.S Posi is a trade name

 

A. did u have the car running? B.
was the car in gear? and C. are u a NO MIND ????

 

so what cars came with lsd? i have an 84 parts car with discs in the back, ill try out the spin thing later but just wondering which models had it or if it was an option ya know...

 

I was always under the impression that only GSLs and SE had LSD. Im probably wrong though.

 

Woah!

This thread is a year old! I haven't seen Manntis post in ages

Yes, only GSL, GSL-SE and cars modified to have the rear ends from said cars have LSD and Disc brakes.

So for example, my GS may soon have a GSL rear end in it, so it would be a GS with LSD

Jon

 

Thougt so. Oh, and does anyone know the stock gear ratios in an 85 GSL?

 

so anything with discs had lsd?

given that the discs are stock of course

 

YES, any 1st gen with rear discs had LSD.

They were the GSL and GSL-SE models.

 

it is poss. that over the last 20 years or so someone other than yourself could have changed the 3rd member to a lsd unit.....take it apart and see

 

Huh? Ohhh, Arkansas...

 

Mine doesnt leave marks but it certainly smokes up. Realy old tires are good for something. Plus my diff has wined since i got it and it goes random lsd. can be a bad thing. specialy in mid drift.

 

haha!
yeah, might wanna check that out :-)



On a side note, it's sad to not see manntis around here these days... :-(