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65 Mustang Rear End Lube

 
65gtfstbk
New User
Posts: 36
Joined: 11/07
Posted: 06/22/08 02:06 PM

I've got a stock 8" rear end in my 65 mustang.  What gear oil should I use in it?  I'm thinking 75W90.  Also, should I feel it up to the bottom of the fill plug?

Thanks  

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wazoopizza
New User
Posts: 14
Joined: 06/08
Posted: 06/22/08 04:12 PM

I used 80W90 IN MY 66 MUSTANG.FILL IT UP UNTIL THE OIL JUST START'S TO RUN OUT OF THE FILL HOLE.  

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60srefugee
New User
Posts: 45
Joined: 01/08
Posted: 06/27/08 02:05 PM

What he said! I also suggest using synthetic gear lube!

Harry  

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65gtfstbk
New User
Posts: 36
Joined: 11/07
Posted: 06/29/08 05:01 PM

Ok....that's what I used.  Seems that it was real low.  I was hoping this would stop the whinning that occurs when I take my foot off the gas when the car is running 30 mph or more.  I also moved the transmission into neutral at about 35 mph and the car still makes this noise.  Anyone have any Ideas????  I'm afraid the gears are either worn and/or don't line up properly.

Thanks  

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soaring3
Enthusiast
Posts: 440
Joined: 03/08
Posted: 06/29/08 05:37 PM

That's entirely possible.  But spend the 65 Bux to have the old dino oil drained out of there, and put in the 75W90 synthetic oil.  Places like jiffy lube can do that for you.  Your gears may be worn, but they still have a ton of life left in them.  
soaring3

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mechanicalguy48
Guru
Posts: 854
Joined: 12/07
Posted: 06/29/08 10:19 PM

Its also possible that your rear end whine is caused by a sloppy pinion bearing. I doubt that changing the oil will affect that. A loose pinion bearing will cause the gears to change pitch under different loading conditions. I am not saying thats it ,,,, just offering another possibility.  

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jlg2002
Guru
Posts: 1410
Joined: 03/08
Posted: 06/30/08 12:34 PM

That whine is due to wear and I don't think an oil change is going to help.  

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soaring3
Enthusiast
Posts: 440
Joined: 03/08
Posted: 06/30/08 04:28 PM

You sound real positive about your answer, but in fact I have quitened down many a rear ends with an oil change.  Yes, there is no doubt that the pinion gear is worn, but still has some life left in it.  In the old days with the 1930's model A's, they used to put saw dust in the rear to quieten it down.   Ooo  
soaring3

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jlg2002
Guru
Posts: 1410
Joined: 03/08
Posted: 07/01/08 12:51 PM

Yeah, maybe I'm getting too cynical in my old age.  I drove a 63 nova for several years with a whining rear-end, It was going good until I "jumped on it" one to many times and blew the pinion bearing right out of the punkin. ( maybe I'm scarred)
Smile  

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65gtfstbk
New User
Posts: 36
Joined: 11/07
Posted: 07/03/08 02:39 PM

I filled it up with 80W90.  To my supprise it took about 2 quarts. I drove the car shortly afterwards and notice no change in the whinning.  The next day I had a huge puddle of gear oil under the car.  I crawled under and noticed it was leaking from around the pinion assembly.  It's been several days now and it's still dripping out.  I'm thinking I've got a worn pinion seal and gears.  I'm thinking of replacing the 3rd member with a 67 or later 8in trac loc.  I'm also wandering if the splines on the axles are worn.  I guess I'm going to have to take it apart to find out. Frown


Also, I noticed a tag.  It has two lines of info.  The first is CZF the second is 3.00 4JD 901.  I fairly sure I have a 3.00:1 ring and pinion set.  I'm not sure what the other info is.  Can someone help me with finding out what the info on the tag is?  

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mechanicalguy48
Guru
Posts: 854
Joined: 12/07
Posted: 07/03/08 02:49 PM

The 3.00 is the ratio, the 4JD is the date built(yr, month , week) and 901 is the plant code. You have a leaking seal because the pinion bearing is worn and causes the pinion itself to move around,,,that in turn blows out the seal. Trac loc 8 inch pumpkins are hard to find and expensive. Your axles are most likely fine but when your in there replace the outer bearings also and your car will be much smoother to drive.  

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65gtfstbk
New User
Posts: 36
Joined: 11/07
Posted: 07/04/08 03:29 PM

Hey, thanks for all the help.  One last thing.... Will a 8in rear end from a 69 mustang fit underneath my 65?  Also, if I were to remove the 3rd memeber from this rear end would that fit into my 8 in. rear end in my 65?

Thanks again.  

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mechanicalguy48
Guru
Posts: 854
Joined: 12/07
Posted: 07/04/08 06:45 PM

The housing will not fit because it wider, the (3rd member)pumpkin will fit if its an 8 inch and uses 28 spline axles (most do).69 Mustangs used 9 inch also, and they will not fit. Your exchanging one old 3rd member for another one, might be the cheap way but if it was me I would just repair the pinion bearing in the one you have.
You can find Ford 8 inch rear ends in Mustangs/Cougars/Comets/Fairlanes/Torino, almost anything that came with a small block 289/302 so there are plenty out there. Only 64/65 Falcons with 289 used the same width as Mustang.  

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soaring3
Enthusiast
Posts: 440
Joined: 03/08
Posted: 07/04/08 08:08 PM

The 65 axle is 57 1/2 inches long, and the 69 is 59 1/2 inches long.  That will give you one inch on each side to poke out.  Not a good idea.  What is wrong with overhauling your current pinion gear?  Sounds cheaper to me, and a whole more of a fit than a 69 would be.  
soaring3

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