Getting ready to drop the rear differential cover to change the fluid (48K mileage). I bought a new cover with a drain and fill plug to make future changes easier, as I plan to change the fluid every 50K.

My question is that the owners manual calls out for 75-140 synthetic fluid with the friction modifier, but the site I'm buying from (latemodelrestoration) is selling Royal Purple synthetic 85-140 and the friction modifier.

Is the slightly higher weight alright?

 

While I recommend caution with changing lubricant weight, since you live in central Florida I don't think going to an 85 will do harm.

 

Meh... royal purple...

Find some good lucas 75-140 syn.

 

Royal Purple 75W140 Max Gear already has the additive. I have been tracking my car for two seasons with this and no issues.

 

Thanks. Wasn't sure why (other than an additional sale?) they included the bottle of Ford friction modifier with the Royal Purple. I'll just shelf it and use it on the next rear end fluid change if I use oil without the already added friction modifier.

 

Sometimes the amount of friction modifier content in the RP gear oil isn't enough to keep the diff clutches from chattering.

 

I contacted latemodelrestoration; They're response:


"The fluids and friction modifier we include in our kits are based on our own experiences of road racing, drag racing and daily use with these cars. We are aware of the manual specs and recommend theselubricants based on our own testing and experience.

The Ford Friction Modifier is recommendedwith the Royal Purple as well."

 

I used Torco RGO (racing gear oil) in my old GTO w/ the type F modifier. That was recommended by guys on ls1gto.com. It worked great. I believe it was 85w140.

Is the automatic gear oil the same as the manual?

 

As in automatic transmission fluid? No. Not even close. If your refering to the rear gear oil, then yes, both a manual or an automatic call for the same rear differential oil.

 

Maybe, in fact I'm sure, this has been asked before but how often is it recommended to change the diff fluid?

 

This all has to do with how the car is driven. If you are just driving it as a DD or even just on weekends, every 30k miles should be fine. If you are taking the car on the track (road course), you will want to do it more often than that. My car usually sees 8-10 days at the track a year, and I change the rear end fluid at the beginning of each season, which is about every 10-12k miles. I have been using RP 75W140 (no additional friction modifier) fluid in the rear end with no issues, but then again, my car has a Torsen instead of the Track-Loc.

 

Thanks yeah not transmission fluid. That calls for every 100k or maybe even 150k miles so I'm gonna leave that alone

 

I wouldn't. I had mine flushed at 30K, and plan to do it every 30K thereafter. I don't understand why they call it "lifetime" fluid; no such thing.

Living in Florida, and doing any type of city driving is going to cook the automatic transmission fluid. Heat is at the top for automatic transmission failures, so I have my automatic fluid flushed every 30K. Been doing this on my previous vehicles for 30 years now, and I've never had a transmission failure, or any ill effects witha flush.

I first went to my Ford dealer to have it done. They quoted me in the area of $150.00, but that did not include dropping the pan and changing the filter. I ended up using AAMCO and paying $160.00; this got me the filter replacement and a flush.

The differential cover replacement and fluid change was eventless, except for the Africa hot day we had in Florida this past weekend with high humidity. I would strongly recommend buying one of those hand pumps that screws onto the 1 quart gear fluid bottles; that makes adding the fluid into the fill hole a breeze.

 

"Life time" to a car maker is "if it last pass the warranty". Just saying..................

 

*I know more that the cars designers do!*


Come on guys... I rarely see these sealed trans fail early. The fluid isnt "lifetime"... service is called for at 150k. The dealers and ford makes money on flushes. They would want to do them to make money. But they know they are not needed in these transmissions till 150k.

Change the fluid early if you want. Its your car. But dont go calling out the designers when you dont know their design. Let alone how it even works...

 

It really bothers me when people say "they don't care what happens after the warranty expires". With all the big three have gone through the least 10 years or so, they (and must car manufactures) do care what happens after the warranty. People are keeping their car longer nowadays and any car that don't last past 100k is just not going to sell no matter how beautiful it is. Reputation is extremely important for car manufacturers. One of the main reason Japanese cars gained so much market share here in the USA, or it is not?

Sorry for the rant, just needed to get it out of my chest LOL

 

I simply will not leave any type of oil in a "friction producing" device for 150K.

If it were a lease, then I would not care; but I make payments, and plan to keep it beyond 150K.

My 2004 F150 currently has 126K, and it's running great. I've been using the same maintenance schedule on it as well.

I can appreciate the the quality of the cars these days, which is why I continue to give Ford my business. It won't however change my maintenance I do with them.