[guy1138]

Wife took the T-bird into an independent shop, where they replaced the rear diff fluid (it was overdue, car was at 120k mi).

While they put in the Ford Motorcraft 80w90, which the manual calls for, they didn't add the friction modifier. Since she has the XE rear, that's a problem.

Here's my question: Can I simply drain out a little bit of fluid with a pump and add the 2 bottles of friction modifier? Or should I try to drain out as much as possible and add the Motorcraft 75w140 that dirtyd0g recommends?

I really don't want to take the cover off, I figure that they got all of the old fluid out when they had it off on Tuesday, so even if I don't get all of it out, at least it's new, clean fluid. Is it ok to have the two different viscosity oils mixed though?

Last question, why do I always do my research *after* it's applicable?

 

[jhosler]

I think if you just took a little out and added the friction modifier, you would be fine.

 

[DisturbedBird]

all you gonna have to do is drain a little out and add a bottle of the additive to it and youll be fine. my books here at work say 80w90 so id stick with it. you do that then youll be just fine

 

[guy1138]

Ok, that's what I wanted to hear. I figure change it after another 50k if we still have the car.

 

[DisturbedBird]

i looked at the book strait from ford and motorcraft and thats what is recommended. just put in the additive and roll wit it

 

[sweet99]

Wife took the T-bird into an independent shop, where they replaced the rear diff fluid (it was overdue, car was at 120k mi).

While they put in the Ford Motorcraft 80w90, which the manual calls for, they didn't add the friction modifier. Since she has the XE rear, that's a problem.

Here's my question: Can I simply drain out a little bit of fluid with a pump and add the 2 bottles of friction modifier? Or should I try to drain out as much as possible and add the Motorcraft 75w140 that dirtyd0g recommends?

I really don't want to take the cover off, I figure that they got all of the old fluid out when they had it off on Tuesday, so even if I don't get all of it out, at least it's new, clean fluid. Is it ok to have the two different viscosity oils mixed though?

Last question, why do I always do my research *after* it's applicable?

I also used the 75W-85 but would use the 85W140 the next time the cover is off as Ford changed the spec. *after* is what I do after buying some part. I try to do a LOT of research about a mod now. I have researched Alan's 10" converter to where I can no longer make a decision on it! Another thread. ark