Crown Vic gear oil?

[HawkeyeScott]

Any help on this would be great...

I have a 1997 Crown Vic LX I bought 2.5 years ago with 71K miles. It's at 103K now and is my everyday commuter, 15 miles each way. I need to get a few things done to it, and next on my list is tranny fluid flush/new filter, and changing the rear end fluid. (I plan to use a MityVac to empty the diff., rather than a full dismantle.)

I do NOT know what fluid to use in the rear-end. Searching yielded little. I don't know what rear-end the car has, so I don't know if I need dino or synthetic, or what viscosity. Again, this is not a heavy duty cop car, just a granddad commuter. Also, I will likely have the car until the fall, when I will sell it. I want to get this done now, get that satisfaction, and then sell a good car to the next guy.

 

[JustinH]

You want a full synthetic 75w140 gear oil.

If you have a limited slip rear end, you need to add friction modifier as per the ford book.

But there are some very good fluids that come pre blended with enough modifier in them for limited slip use, but they are still appropriate for non limited slip use.

An example would be royal purple fluid.

If you consider the cost of buying the friction modifier seperate from the gear oil, versus buying royal purple, then the cost is about the same, so I say buy the premixed gear oil and be done with it.

I have used royal purple in several rear ends, and its fine.

 

[Jim 5]

I would be very surprised if the factory spec wasn't 80w90 GL-5. Call your local ford dealer to check if you can't find it online. My guess is you'll need 1-2 qt's to finish the job. If you have a diff cover, you might find it to be easier just to take off the pan.

If you want to go the mityvac route, be sure to to this after a good long drive so the lube is nice and heated up so that it can more easily get through your suction gun.

 

[Pablo]

I think this differential runs very hot. The book originally called for 75W-90 (90). Somewhere along the line someone (Ford?) decided 75W-140 would be good. I think the best would be:

Amsoil 75W-110

If you want to go heavier:

Amsoil 75W-140

 

[HawkeyeScott]

I just checked, there is no drain hole, so it looks the MityVac route is a no-go. Full cover removal, it looks like.

Thanks for the quick responses.

 

[ewetho]

Ford changed gear oil requirements from 75w-90 to 75W-140 so go that route. Amsoil would be great.

 

[ConfederateTyrant]

Factory manuals say 80w-90, I've used Amsoil 80w-90 and currently using Amsoil Severe Gear 75w-90, and no issues have come up with using either in my 1995 Mercury Grand Marquis. I think a synthetic 90 weight is going to protect the gears far beyond that of any non-synthetic 90 weight.

As for what Pablo mentioned, I'm not sure how hot these differentials run, but to compare two 80w-90 fluids:

Castrol 80w-90 I used for 8,000 miles came out nasty looking (greenish/grayish), and the Amsoil 80w-90 I used for 10,000 miles (changed it as it was my first Amsoil run and it had been in there for nearly 2 years) came out as if I had just poured it from a fresh bottle.

 

[Islandvic]

Please check out link for your Crown Vic needs.

I used Valvoline 80-90 Synthetic Blend in my '96. I pulled the diff cover, cleaned it and the diff housing, and used a Fel-Pro gasket.

I takes 2 qts to do the job.

If the vehicle is a Police Interceptor or has the HPP option, it has a Trac-Lok locking differential, and will need the "friction modifier" additive.

It sounds like you have an open diff ike mine so I doubt you will need it.

The link I provided above will have a resource to determine what diff you have.

Good luck.

PS, your touque converter has a drain plug also. The link will have instructions about trans fluid changes too.

 

[wgtoys]

I recently helped a friend change out the rear diff. fluid on his Grand Marquis (a twin to your Crown Vic). We used Royal Purple 75W-90 and it seems to be working extremely well. No strange noises from the limited slip function.

The vehicle didn't have a gasket from the factory as Ford switched to just putting orange RTV #@$%! on there. The level was rather low as the RTV had started to self-destruct and leak. We purchased a gasket for an early year version of the car and it worked perfectly. Remove the cover and clean out as much of the gunk as you can. Remember to keep things clean, so don't work outside on a windy day atop a sand pile!

 

[JustinH]

Ford has never used a gasket on an 8.8 rear end.

Its always been black RTV.