Solved Differential Swap

[Lee's Automotive]

this is what i do, and i think this what were supposed to use in my 98

rear open- 80/90
rear LS- 75/140+friction modifier
front open- 80/90

i think, brand isnt a huge concern i personally use valvoline or m1 syn, but dunno

I used 75w140 in my rear with the open 3.55

 

[Mbrooks420]

No need for different weights for open vs limited slip. It’s the same gear set. If the modifier is in there, that’s all it needs. I never add any extra modifiers to my rears, and have had zero issues.

 

[Fix4Dirt]

Royal purple with the LS additive already added is ok right? Or should I use a separate thing of modifier? When we cracked the cover off the old one after the shop refilled it there was a greenish color to it, I haven't ever seen that before in gear oil.

i have a feeling its fine, its jsut enough to meet spec but i always added my own dose of the green stuff, hasnt exploded yet

 

[Fix4Dirt]

No need for different weights for open vs limited slip. It’s the same gear set.

i thought the thicker fluid was to help the LS clutches, no?

 

[Mbrooks420]

i thought the thicker fluid was to help the LS clutches, no?

No.

 

[ThatOneGuy99]

i have a feeling its fine, its jsut enough to meet spec but i always added my own dose of the green stuff, hasnt exploded yet

Is the green stuff just the friction modifier?

 

[Josh P]

I use royal purple in the front axle in my jeep, it has a limited slip. Works great and I've never added anything to the oil

 

[Fix4Dirt]

Is the green stuff just the friction modifier?

yeah the friction modifier, forgot what to cal it

 

[ThatOneGuy99]

yeah the friction modifier, forgot what to cal it

Interesting, I wonder why the shop added it to the old axle, it wasn't a limited slip

 

[Josh P]

$$$

 

[ThatOneGuy99]

$$$

I'd like to think maybe they thought it'd reduce the wear on the gears in some way

 

[Josh P]

I'd like to think maybe they thought I'd reduce the wear on the gears in some way

If that was the case, we'd all be running it

 

[Fix4Dirt]

the fric mod does nothin for the gears and reducing wear all it does is reduce chattering, shop probably wanted a few bucks extra for the weekend not sure

 

[Josh P]

the fric mod does nothin for the gears and reducing wear all it does is reduce chattering, shop probably wanted a few bucks extra for the weekend not sure

That's what I'm thinking, you bought the guy a beer for Friday night

 

[Fix4Dirt]

or the shop was clueless how much if ya dont mind sharin did they charge ya? iirc the ford modifier is like 10 bucks MAX, usually mroe like 5 when i get it... if they charged ya 20 bucks or somethin.... think he saw his buddies that night

That's what I'm thinking, you bought the guy a beer for Friday night

 

[ThatOneGuy99]

or the shop was clueless how much if ya dont mind sharin did they charge ya? iirc the ford modifier is like 10 bucks MAX, usually mroe like 5 when i get it... if they charged ya 20 bucks or somethin.... think he saw his buddies that night

They only charged me diag, didn't itemize much of anything. I think it was 447 for them to pull everything apart both front and rear diffs. I'm not impressed because they didn't use a gasket in the rear just a ton of RTV and also stripped out the retainer pin bolt on the carrier.

 

[CDW6212R]

You are fine, a good brand name is sufficient, and the 75/140 was the new required fluid now for about 15 years.

 

[Fix4Dirt]

They only charged me diag, didn't itemize much of anything. I think it was 447 for them to pull everything apart both front and rear diffs. I'm not impressed because they didn't use a gasket in the rear just a ton of RTV and also stripped out the retainer pin bolt on the carrier.

hmm alright yeah i cant think of a legitimate reason to use the mod in the rear...

 

[ThatOneGuy99]

I just really don't want to ever have to fully rebuild either of these things, I can't do it myself without the space and tools and to pay a shop to do it all is hardly worth even keeping the car.

 

[Fix4Dirt]

y

I just really don't want to ever have to fully rebuild either of these things, I can't do it myself without the space and tools and to pay a shop to do it all is hardly worth even keeping the car.

yeah i feel you, i mean the mod wont hurt it, but it aint doin ya no good back there either, makes no difference on open,, just a waste of a few bucs. so cause you got open diff it doesnt hurt ya in any way