curious 'bout differential info...

[Icarus]

I'm curious now from reading alot of these posts on here and FvC...
I changed the fluid in my diff. a week or so ago to Mobil1 synthetic, and when I ordered the gasket for it, the only listing this store had was for a 7.5" or a 8.5" cover... I have an '86 LSC and thought these had 8.8" diff's??? I ordered both & the 7.5 didn't come close to fitting (too narrow) but the 8.5 fit... Is the gasket the same for 8.5" and 8.8" or do I have some oddball differential??? Any quick ways to tell? Theres no tag on it... and I don't know the whole history of the car...
Thxs for any help/info,
Jon

[KULTULZ]

The '86 came with either the 7.5 or 8.8 rear. You obviously have the 8.8. There is no 8.5

The rear cover is different for either.

What is your rear axle door code?

[Icarus]

Where do I find the code? The listing at the parts store said 7.5 or 8.5... no 8.8 :(

[Kev Schofield]

Lots of good info if you dig through the Mark VII Archive forum..I got this from there.

Read the AXLE CODE on the driver's side door tag to see what ratio you have. (the sticker is close to where the door latches) Look under the "AX" column and you'll see one of these:

"E" is a 3.27:1 Trac lok
"5" is a 3.27:1 open end.
"Z" is a 3.08:1 Trac lok.
"Y" is a 3.08:1 open end.

Hope that helps.

[Icarus]

Thxs very much for the info Kev & KULTULZ smile.gif
I checked out the code, it says '5' under AX
I'm wondering now.. why would both tires break free on dry pavement if I give it a good shot of gas and not just one (its always both of em)? I thought the open diff. meant 'one wheel peels'???!!! ;)
Thxs again,
Jon

[ November 15, 2001: Message edited by: Icarus ]

[WILLIAM SHIREY]

I don't know about an '86 LSC but my service book for the '85 (and also the Haynes book) says to use silicone in lieu of a gasket. You must clean both surfaces well, scraping off all previous gunk and run a bead around each bolt hole as well. Napa guy recommended a hi-temp red colored silicone.

[Lscman]

Original 7.5 and 8.8 diff's had no cover gasket. They used permatex. Ford used to identify the 3.27 gear as 8.7" to avoid lawsuits. It is the 8.8" form factor. 8.5" is a misnomer and has not been used by Ford since the '70's.

[ November 20, 2001: Message edited by: Lscman ]

[Icarus]

K, sorry if I'm starting to get confused... :confused:
So it is an 8.8" diff???
What bout finding out if its TrakLoc or not?
I didnt think an open diff would let both tires go unless it was wet out or on ice etc...???

[KULTULZ]

It is an 8.8. The easiest way to determine if it is Traction-Loc is to jack the rear axle up and turn one wheel (by hand). If the other rotates in the same direction, it has Traction-Loc. If it rotates in the opposite direction, it is open. You can also pull the cover again, and if there is a large "S" spring between the two axles shafts, it is Traction-Loc.

Remember, the rear may have been upgraded at some point before you got it. It is possible to spin both wheels (on take-off) if there is enough engine torque available.

Not to blast the NAPA guy, but Black RTV (Permatex) is best to reseal the cover.

[Icarus]

According to what I've learned from you guys (btw, thank you very much!) I have an 8.8 with TracLok (the tires do spin the same way)
Next step...
see if it is indeed 3.27's I have in there, cause the sticker says I have 3.27 open diff in it... musta been messed with in the past!? ...could explain why my speedo seems out too smile.gif
Thxs again for the great info guys!
Jon

ps: I did buy the gasket just fer the fun of it :D I changed fluid before without.. just a lil change this time ;) hehe

[ November 16, 2001: Message edited by: Icarus ]

[Icarus]

This means when I goto get gears for this diff in the future (next summer?!) that I CAN get 8.8" gears (4.10's!!)???
Thxs again,
Jon