ym42

So I am having a small leak from a pinion seal. Its been a year and I am too cheap to spend 250$ to fix it ( should I? ). Anyway, after driving about a year and 30000 miles I decided to top off the fluid a bit, just in case. It was about a pint low. I got some Valvoline synthetic blend 85-140 gear oil from local AutoZone store, cheap, made by Valvoline. Did not add the modifier... I noticed on some forum pictures the differential cover says "synthetic only". My gut feeling is saying I should be ok with my temporary solution, but what do you guys think? Should I pay 250$ and get this fixed, or just top it off every 20k miles? Would this 75/140 stuff be OK? ( I think the repair manual says 75-90? ). Any ideas?

Art161

My idea is to get the car repaired properly.

If not, at least use the correct products. I don't know what the specs are for 2006, but for 2007, it is 75W-140 SYNTHETIC. And why didn't you use some friction modifier? If you replaced one pint of fluid, you should have added about one ounce of friction modifier.

ym42

Well, the store I went to did not have the modifier... I guess gonna add some next time... The reason I am OK with semi-synthetic because the only one reason I can think they put synthetic only is so that the fluid does not need to be changed... I think longevity of synthetic lube must be the only difference... If the leak gets worse I will have to replace the fluid anyway...

smokestang

Even with synthetic it still needs to be changed. mixing non-synthetic in with synthetic cant be very good IMO. as for the leak itself, id def fix it. it will only get worse with time! if youre gonna get it fixed, it would be a great time to get 4.10s as it would only cost around $500-600 to do everything and be done with it. thats what my buddy recently did when his seal went bad.

tx_zstang

$250 to fix the leaking pinion seal? wow. might as well do gears while you're at it!

A-line auto parts carries the ford friction modifier.

If you're just adding a little to the rear end, you shouldn't need to add any modifier. But, keeping with synthetic 75w-140 is the right way to go.

howarmat

my pinion was leaking too...cost was 210 for new pinion seal and some fluid. So i would see if you can find a place to do it a little cheaper maybe but i would have it fixed. It might lead to more problems later

MustangMan1718

I work at a VIOC and we obviously have Valvoline fluids. The 75-140 is a full synthetic fluid, which should be fine. I've actually never heard of 85-140 though (We have 75-140, 75-90 for our synthetics and the foul-smelling 80-90 for the conventional fluid).

I'm also embarrassed to say that I have just recently learned about friction modifiers within that last week or so. We don't carry anything like that, so I have never use them.

But if you want to go the cheapest route, VIOCs have a free top-off policy on any fluid within every 3-months or 3,000 miles of an oil change you get there. So you can be like the Cadillac folks that stop in weekly for ~3 quarts of oil in their Northstar engines except for a rear diff. topoff.

And as I always say, I hate to sound like a salesman and promoting the place, but when you say it so frequently over three years, it kinda gets engrained into you.