1inthechamberFC

so i changed the diff fluid in my last fc cause it wasnt locking up well, and right after i changed it it'd leave solid black marks and lock up good. i recently bought another fc, 87 gxl which i thought had lsd since its a gxl. i jacked up the back and spun on tire, the other one didnt move which SHOULD mean its got lsd, if the other tire spun the opposite way it'd be open diff. anyways, i changed the fluid in this car with supertech 80/90 and there was no change in lockup, then i bought a 7oz tube of lsd additive the next day, drained the pumpkin, put more new gear oil along with the additive and still nothing, so im thinking wtf does this not have lsd or is it just tired as ****. so my question is, should i be using a specific type of gear oil, like redline? and if so should i get the 75/90 or 75/140 and with or without the friction modifier? any help would be appreciated!
thanks

89_Rx-7_GTUs

i believe only GTUs and Turbo II came with LSD's!

1inthechamberFC

whattt are you serious? i read somewhere on here almost all 86-88 had clutch type lsds and the s5's had vlsds? i know for a fact my 86 had an lsd and it wasnt turboII or GTUs
hmmm

Rx-7fetish

Yes the 87 gxl had an lsd, 89 and later do not, i just looked this up in the specification sticky at the top of this forum

fcforlife

iTrader: (9)

ok well if you have lsd and the car is in neutral then both tires will spin the same way. if it is not in neutral you will have opposite way spin after it breaks the lock. and i would suggest checking the clutch plates for size. making sure they are not worn down past spec. because if one wheel didn't spin thats not good. both wheels should spin. if you have a stuck caliper on one side then your spider gears will have gone through hell. i'd say pull it out and check it out.

1inthechamberFC

hmm thanks for the responses. i jacked up the back of the car again and had a friend hold the opposite wheel and i spun one and they will spin freely, way open. so ****. i have another fc, also an 87 and we jacked that up, did the same thing and it was hard as hell to hold one wheel with the other person spun the other, so it seems to be locked up? right? so knowing that, im either gonna weld the open diff tomorrow or maybe swap the rear end from the other car into the open. anyone hear anything good/bad about welding diffs in fcs? all the 240sx guys i know do it with no problem.
thanks again.

Black91n/a

It's 21 years old, don't expect it to be like new. It's probably just worn out. Rebuild it.

Josh18_2k

iTrader: (3)

if you wanna get fancy, a miata torsen diff is a killer upgrade to an N/A. they might be expensive tho.

1inthechamberFC

im just gonna weld it, see how it goesss.

Black91n/a

A welded diff is a bad idea on the street. The tires NEED to be able to go at different speeds in order to turn, so now they'll be forced to slide along the pavement to make up the difference, which will make it much more difficult to turn, especially at low speeds such as when parking and will caused increased understeer on turn in.