Anyone know how to tell if its a limited slip differential? I would like to change the fluid soon and dont know if I need to add the additive for limited slip diffs. Thanks!

 

You can look at the tags on the diff. There are posts on how to decode them. I mostly jack up both wheels & turn one--if the other turns the same direction, it's LS--if it turns the opposite way, it's an open diff.

------------------
97 Lariet-sc-4.6-4x off road-auto-3.55 LS-
superchip-K&N-3"
pvc air box mod-Granetelli MAF

 

You could always try to spin the wheels. Find yourself a nice little flat dirt patch and stand on it. 2 stripes = LS

------------------
2000 XLT SC FS, 4.6/5-spd, 3.55 LS, 4X4 Off-Road, Black w/ Silver 2-tone. Pro-chamber Cat-back exhaust w/dual 3.5" chrome slash cut tips, K&N Filter, AutoMate alarm w/keyless entry & pwr window control, Air Horns, Bugflector, Cowl cover, Window shades, Carbon fiber headlight covers.

 

Yeah Ive tried spinning the tires in the dirt but I think there is enough horsepower to spin them regardless of wether its a LS. I guess I will have to try to get some spin goin on the pavement and see if they both spin.

 

I thought my truck was LS but it is a open unit. But the strange thing I can leave two stripes on any pavement.

 

Look inside the driver's side door on the sticker. There should be a code for your axle. Match this code with the ones listed in your owner's manual. For instance, I have a '95 with an axle code of "H9" on the sticker. This translates to a 3.55 LS in my owner's manual. I'm pretty sure the '97's are the same.

 

Look on the sticker on the door if it has a X in front of the number its a open rear end if it has a H its a LS rear end.

------------------
2000 F150 XLT Reg. cab
4.6 Triton Engine
4x2 3.55 rear end gear
sliding rear window
automatic keyless entry
white styleside short box

[This message has been edited by hmustang (edited 01-20-2001).]

 

Actually I think the open diffs have two numbers and the limited slips get a letter and a number. Here is a list of common codes that I've found posted before...

12 2.73 3800 FORD REG
18 3.08 3800 FORD REG
19 3.55 3800 FORD REG
25 4.10. 5300 FORD REG
29 3.55 5300 FORD REG
35 4.10. 6250 FORD REG
39 3.55 6250 FORD REG
45 4.10. 7400 FORD REG
49 3.55 7400 FORD REG
65 4.10. 8250 FORD REG
69 3.55 8250 FORD REG
72 4.63 11000 DANA REG
73 5.13 11000 DANA REG
H5 4.10. 3800 FORD LIMITED SLIP
H9 3.55 3800 FORD LIMITED SLIP
H8 3.08 3800 FORD LIMITED SLIP
B5 4.10. 5300 FORD LIMITED SLIP
B9 3.55 5300 FORD LIMITED SLIP
C5 4.10. 6250 FORD LIMITED SLIP
C9 3.55 6250 FORD LIMITED SLIP
D5 4.10. 7400 FORD LIMITED SLIP
F5 4.10. 8250 FORD LIMITED SLIP

3.73s are missing from this list, but I think the last number is a 6. So that would be like 16 or H6 or something like that, depend on what the 3800, 5300, etc mean in the above list. Anyway hope this helps...

 

the simple way is to look on the diff tag, for example if it says 3L55 then u have a limited slip 3.55 ratio , if it just says 3 55 then u have an open 3.55 ratio, same with other gear ratios just chek for the L. By they way there should also be another tag (two in total) one stateing to used sythetic 75w/140 gear oil (late models use synthetic early ones dont-hence no second tag)