Turbo LSD in NA car

[seth959ci]

hello everybody, just wondering how much a 3.91 LSD will throw off my speedometer in my NA car.. anybody know? thanks

 

[AJ'S 88NA]

Are you sure you don't have one? I do and mine is NA.

 

[bioskyline]

my 88 parts car has a lsd. also whats the axle code on your car ? its on the plate under the hood. then i can tell you more

 

[seth959ci]

i found a set of numbers on the firewall.. is that the correct set?

 

[bioskyline]

yes, it will have ax or axle under it. should be 3 number

 

[seth959ci]

ohh,,, i found a 7 digit number... hang on a sec... cannot find just a 3 digit number... just what appears to be the VIN

 

[Devin LeBlanc]

NA's came with 4.30, Turbo came with 3.91 and 3.7

 

[seth959ci]

the reason i am interested in an LSD is because i live in the country and want to have some more traction for when the roads turn to crap in the winter... also i think my open diff is goin bad. a vibration has developed over the past couple days, it will vibrate and then smooth out and repeat the cycle. i crawled under the car and found slack in the driveline but all the U joints seem to be ok.

 

[AJ'S 88NA]

the reason i am interested in an LSD is because i live in the country and want to have some more traction for when the roads turn to crap in the winter... also i think my open diff is goin bad. a vibration has developed over the past couple days, it will vibrate and then smooth out and repeat the cycle. i crawled under the car and found slack in the driveline but all the U joints seem to be ok.

Have you checked the center support bearing?

 

[seth959ci]

yeah it didnt seem to be that... may check it out tomorrow to double check

 

[bioskyline]

or give me all the numbers i can figure it out

 

[seth959ci]

ma70 0160212..thanks for the help btw

 

[bioskyline]

ok thats the wrong tag, its a silver tag that rivted on, should be just above the brake booster.

---------- Post added at 06:33 PM ---------- Previous post was at 06:27 PM ----------

tag should look like this

 

[seth959ci]

umm.. there is no tag located above the brake booster... i pretty sure its not an lsd... will not do dual tire burnouts.. also LSD is not listed on the original window sticker i have

 

[bioskyline]

do you know what gears your car currently has?

 

[seth959ci]

not for sure but im betting it has 4.30... pretty high rpms on highway.. around 3000rpm at 65mph

 

[hvyman]

Look on the door jam sticker. Iirc it will say something like g35 or g30 or something like that. I think i have seen more cars with that under hood plater missing than with them still there. idk why either.

Regardless n/as only came with open or 4.30 lsd with sport package. Easy to tell if you lift up rear wheels. and spin 1 tire the other side should spin the same way if you have a lsd.

 

[plyhard13]

Whether you have and LSD or open, your diff will be a 4.30. Switching to a 3.90 will cause your speedo to read higher than the actual road speed. There are really only two things you can do. The right way is to get the actual speedometer gear from a transmission with a 3.90. The other way would be to use GPS to measure against the indicated speed on the speedometer. Say for example, your speedo shows 80Mph and the GPS shows 73Mph. 73/80*100 = 91.25% 100-91.25 = 8.75% difference between actual speed and indicated speed. Thus no matter how fast the speedo shows, you will actually be traveling 8.25% slower. Obviously, this would require you to already have the new diff installed.

 

[hvyman]

There is an adjustment in the speedo itself. I forgot who did it but there is a write up about it. Idk if it was here or the other(now super ugly) site.

 

[northdakotakid]

There is an adjustment in the speedo itself. I forgot who did it but there is a write up about it. Idk if it was here or the other(now super ugly) site.

I gotta find this writeup, I am in the same boat as the OP