75w140?

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In my 1988 Ford F150 it has a rear 8.8 axle. I saw the other day after repairing the rear brakes that I have a seal leaking and it's probably the explanation of why I hear a roaring noise over 65 miles per hour. I'm plan on replacing the bearings and maybe getting the whole unit rebuilt but I want to put oil in it in the mean time should I use a thicker oil like 75w 140 to slow its leak down and how do I know if it's a track lock
 
I'd guess a thicker gear oil would leak more slowly.
Check for a rear axle code on the door jamb or have the VIN run at a dealership.
I don't know if there's a tell-tale sign like a differently shaped diff cover.
Where would you go for the rebuild? Ask them.
 
Ford, at least my local dealer don't help much with older vehicles. I've tried before with the VIN and he will say it don't show up, then he will ask what year I'll tell him 88 and he says that's why. They don't support older fords for some reason. At least fairway ford in greenville sc. So no help there. I can look for parts here with year and model but nothing specific to its VIN.
 
One way to check for a limited slip differential, if it is working, is jack up both rear wheels off the ground. With parking brake off rotate one of the tires in a forward direction. The other tire will rotate in response; in reverse direction if the differential is open and forward if the differential is a limited slip.

You can also log on to Ford-trucks.com with your axle code in hand and ask there. Those guys know everything.
 
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Worth a try but it didn't help me with my 87 f150 (8.8) when the axle shaft seal leaked two years ago. A new seal did, my bearings were still good..
 
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The vent was plugged however the case was full of oil. So maybe this leak is slower than I thought. I guess I can ride a little longer until I get new bearings in it cuz it makes this roaring noise on the highway it's not real bad it's more like a vibration but I'm pretty sure it's coming from the rear. I've already had my tires checked once
 
Originally Posted by mpack88
The vent was plugged however the case was full of oil. So maybe this leak is slower than I thought. I guess I can ride a little longer until I get new bearings in it cuz it makes this roaring noise on the highway it's not real bad it's more like a vibration but I'm pretty sure it's coming from the rear. I've already had my tires checked once

If you let it go too long with a bad bearing you stand to have to replace the axle shaft because it serves as the race for the bearing. You have to remove the rear cover, a couple bolts to remove a cap to gain access to the c-locks which need to be removed to pull the axle out. I would reseal both sides. I would have a good technician look at it. You will need access to a press for the bearing . Just make sure it is not a u joint causing your vibration. If you see powdered rust on it, it is bad.
 
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Originally Posted by zeng
Originally Posted by Slick17601
I would go with an 85W-140 conventional gear lube.

+1

I had done this by mistake the first time around, and in my case it was Delo ESI 85-140. Has been fabulous in that nefarious Ford 8.8, Those are especially leaky if you have prolonged highway runs. I had that after a few coast-to-coast road-trips (although the unit had more than 200k miles by then).
Mr Zeng helped me to clear my head then, thank you. Now I pay attention to ISO numbers, apparently that is what engineers go by.
 
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