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Discussion Starter · #1 ·
Hey guys this is my first time at this forum and I'd like to ask a few questions. I recently traded my nissan pickup for a 1986 mustang lx 5.0 I'm happy with the trade, though at 35 mph to 50mph I can hear what sounds like some rear end whine. I thought I'd change it and hopefully reduce the noise. what gear oil brand and weight would you guys recommend? The car has 200,000 miles on it, with a surprisingly decent amount of power left.

Also I was wondering if 20w-50 motor oil would hurt this car. I'm doubting it, but I've had it for about 2 weeks and it gets ragged on a bit at least once a day. Some say that thats a bit too thick? It averages about 80 degrees outside where I'm at now. I know with the 10w30 it has now, it needs a quart every time i stop for gas.

For info on the car, It has an msd distributor, cold air intake, bbk off road h-pipe with 2.5 inch flowmaster exhaust. I have a set of bbk shorty headers that came with the car that i will be putting on eventually. IT burns oil like hell though. And leaves some smoke.

And also, the trans is a world class t5 correct? so that takes dextron II if i recieved the information right...
 

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A stock T-5 takes mercon ATF 2.8 qts.
 

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Discussion Starter · #3 · (Edited)
Oh. Ok. I was making sure because I heard the earlier T-5s took 90 weight gear oil. So dextron mercon atf will work fine? and i was wondering if I could add some of that lucas automatic transmission fix to it to reduce the wine of 1st 2nd and 3rd gears... I tall that stuff does is thicken the fluid...

And does anyone know what rearend I have? I remember seeing in the owner's manual that it's a 7.5 inch. But people have said that I have a 8.8. It is an original 5.0 car. Gear oil guys? 200,000 miles. Someone said 75w-140..... I just want it to last a little while longer. If it's 7.5 rear i will be changing it to an 8.8 or a 9 sometime in the future. But for now I want to change the rear differential gear oil to hopefully reduce the whine noise and to make it last for a while. So what weight gear oil would be best to put in and should i put any additives?
 

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With that amount of miles, 20W50 isn't too thick. The bearings are worn and so are the rings so you could use the thicker oil. It might be a tad thick for wintertime, maybe drop it to 15W50.
For the burning oil, does it smoke at cold start up, or after it warms up, or both? It's probably tired and needs to be freshened up.

And is the whine from the transmission or rear end?
 

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Discussion Starter · #5 ·
Ive got whine from the transmission from 1st gear until 3rd. 4th and 5th gear don't whine. While rolling in neutral at about 35-50mph, some rear whine is noticable. And I want to op that as much as possible.

As for the engine smoke, it doesn't really smoke on cold start up. If you rev it up say at a light, or take off from a stop sign it will leave a small cloud of blue smoke. Sometimes after a hard pull and you stop, it will smoke at idle for about 5 seconds. I know it's a bit tired, but surprisingly it runs well and pulls decently. It doesn't smoke really at all on cold starts. Once it warms up it tends to smoke a little more. It also runs really rich sometimes so it blows some fuel smoke sometimes. More on the white side.

But like i said, it smokes more when warm, and when you rev it up it smokes. While revving. Stops when you hold it at a constant rpm.

That i'm not really worried about. What i'm most concerned with at the moment is making the rear last as long as possible. One thing I forgot to mention, above 50mph, there seems to be a vibration in the stickshift. Its a very low frequency hum. This is in neutral going down a hill at about 55mph and up.
 

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Sounds to me like your U joints maybe. Have you checked them out? I never had this problem with my Mustang but I did have it with an old Aerostar van. I definitely did sound like it was coming from the rear end, but replaced the U joint and the noise and vibration were gone. Check both joints at the yoke and the rear end you might be surprised. They are a little cheaper to replace then a rear end or transmission. Good Luck!
 

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Discussion Starter · #7 ·
thank you. The high pitched whine is from the trans, i know that. What weight gear oil is best suited for this rear? and is it an 8,8 or a 7.5? it's a 1986 5.0 LX

Ill definately take a look at the u joints. thanks a lot. I don't want to just throw some random gear oil in the car. JW what the mass opinion was.
 
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