80w90 bad for rear diff?

[toddious]

but if it says "for top off only", the only difference would be the modifier correct?

i think i will probably just use the 80w90..... it was cheaper, and i'll probably be reopening the diff. before too long anyway.

 

[Creager]

but if it says "for top off only", the only difference would be the modifier correct?

i think i will probably just use the 80w90..... it was cheaper, and i'll probably be reopening the diff. before too long anyway.

read the bottle? does it say WITH FRICTION MODIFIER?

What size are your gears? It would be way overkill to run 75w-140 in anything smaller then 4.56 esspecially if its open... and like what RangerX said above, the newer 8.8s aint any different then the older ones. I am actually using a Truetrac that was originally used in a 98 8.8 in my 92 8.8... no difference

 

[toddious]

read the bottle? does it say WITH FRICTION MODIFIER?

What size are your gears? It would be way overkill to run 75w-140 in anything smaller then 4.56 esspecially if its open... and like what RangerX said above, the newer 8.8s aint any different then the older ones. I am actually using a Truetrac that was originally used in a 98 8.8 in my 92 8.8... no difference

it does not say with friction modifier, all it says about LS is "for top-off only".

i am only running stock 3.73 gears. however, it does say to use 75w140 no matter what your gearing is.

seems like a lot of people use 75w90, is the difference between the 75 w90 and the 80 w90 going to make any difference? thanks, todd.

 

[Jefe]

From what I've heard the reason the newer models use synth 75-140 is so that the diff oil never needs to be changed. Sealed for life type of thing. I see no problem runnning 80-90 if you're going to be changing it out again soon.

 

[Creager]

i am only running stock 3.73 gears. however, it does say to use 75w140 no matter what your gearing is.

you should be alright

 

[aldive]

seems like a lot of people use 75w90, is the difference between the 75 w90 and the 80 w90 going to make any difference? thanks, todd.

It will make no difference at all.

 

[toddious]

thanks all for the help! i will be using the higher grade (valvoline vs. walmart brand) semi-synthetic 80w90. now i just hope that i sealed up the differential cover sufficiently!!

 

[97BlackX5.0]

it might actually be the same stuff.... someone has to make oil for walmart.... as long as it is the same type of oil it could be the same... ive heard of walmart oil being quaker state and valvoline depedning on which part of the country you get it from

 

[toddious]

interesting.... i will check out the bottle a little more.

 

[CDW6212R]

Todd, if you haven't filled it yet, skip the modifier, and use the less expensive fluid. If you are going back into it in the near future, change to a good synthetic fluid, rebuild the clutches, and use the friction modifier then.

The LS rebuild kits are just over $50. When I build one, I use another pair of clutches from another kit, and install one extra. By rearranging the order of the frictions/steels, you can install four per side, instead of three per side. Those in my 93 were very tight to start with, but they have worked for 30,000 miles.
Good luck,
Don

 

[410Fortune]

I had this same mod done to my factory L/S when my gears were setup.
the friction modifier make it quiter, and slip more. I dont use it.
I want my L/S to grip as much as possible, which with 35's and a heavy foot isnt much hahaha

 

[toddious]

i'm hoping to re-gear the rearend pretty soon, and i will definately rebuild the clutches then too. is there anything else that goes bad with the limited slip? or when i rebuild it with new clutches, it should perform basically like stock? thanks, todd.

 

[wpurple]

According to Ford....

80W90 is recommended, add FR idf it is a LS, unless it is 3.73 or 4.10(4.11) then 75W140 Synthetic is recomended and FM if it is a LS.

I am sure that either weight is fine, I think that they assume that if you have 3.73/4.10's that you may be towing.