rear end difference

bertman · Oct 18, 2006

Have 65 mustang that had a 289 in it. Also have a 66 that has a inline 6 in it. The outside of the rear end look the same. Are they. And if they are what is the difference between the 2:SNSign:

gjz30075 · Oct 18, 2006

They may very well be the same, however, from the factory, the I6 car came with a 7 3/4" rear end which is quite a bit different from a V8 car, which came with an 8". The 8" has the gears in a removable carrier unit, unbolted from the front and the 7" has a plate the bolts to the back of the housing to get to the gears.

Your 289 car could have been an I6 car with an engine transplant and nothing else changed. Or, more unlikely, your I6 car had an 8" put in it.

1966conv · Oct 18, 2006

Another thing to note; the 6 cylinder cars have 4 lugs per wheel and the V8's have 5. The 6 vs 8 are radically different rearends also in that in a "true" 65 V8 the axle tube are tapered where as the 6 cylinder rears are straight tubes.

Without a little more info it's kinda hard to tell what you have. The other poster is correct in that your 289 car could have started life as an I6, and not had the rear end changed, (naughty-naughty) or the 6 cyl car could have been upgraded to a 8" rear end. The 6 & the 8 really don't look the same.

ultrastang · Oct 18, 2006

If you look on the 5th letter from the left on the VIN plate, there will be a letter for the engine code. If it's not an A, C, D, or K, then the car was originally equipped with a 6-cylinder engine.

The base rear end for a V8 Mustang was the 8-inch. Only the HiPo 289s from '65-'67 came with factory 9-inch rear ends. After '66, when Ford started putting big-blocks in the Mustangs, 9-inch rears were used with those engines, but regular small blocks got the standard-issue 8-inch rears.

www.ultrastang.com

killer medic · Oct 19, 2006

I bought my 67 coupe that way as well. It was originally an I6 and was upgraded (engine-wise) to a 302. I am still trying to find out EXACTLY what kind of car the engine came out of (I believe it came from a Comet). That's another topic. Anyway, the VERY day I bought the car, I made the eager (and I think common) mistake of trying to peel-out, then get on the highway before truely inspecting the car (newbie error). All of a sudden, I hear this awful and LOUD roaring coming from the under the backseat. The only time it was quiet was when the car was not moving. I looked underneath the car and there was axle fluid everywhere! I put more in, but the damage was done. I have since replaced the rearend (try to get a friend to help put it in. It sucks to do it by yourself). You may also notice that your speedo reading is way out of whack. Replace that rear-end pronto and everything will be good (rearend-wise). Your engine will eventually tear that rearend apart.

D.Hearne · Oct 19, 2006

killer medic said:
I bought my 67 coupe that way as well. It was originally an I6 and was upgraded (engine-wise) to a 302. I am still trying to find out EXACTLY what kind of car the engine came out of (I believe it came from a Comet).

Don't worry about what that 302 came out of. Trying to find out what it came from is pointless. All applications shared the same basic block/crank/rods/heads with the exception of the Boss 302.

killer medic · Oct 19, 2006

D.Hearne said:
Don't worry about what that 302 came out of. Trying to find out what it came from is pointless. All applications shared the same basic block/crank/rods/heads with the exception of the Boss 302.

Does that also apply to all electrical and vacuum applications? What about compression rations and cam information. If I were to plan on changing the head, cam, and intake, I guess it REALLY wouldn't matter since I have created a whole new configuration. I am just wondering if it is feasible to find out what I have to determine these configurations without tearing it apart (at least not yet). When I go to the auto part store and give the make and model of my car, of course there is no 302 option because it hadn't existed yet. If I told them it was a '68 mustang, would that be feasible, being the close similarities? BTW, how would I know if I don't have a Boss 302 configuration on my hands? I am really curious as hell to see if my engine in on the milder or wilder side. Thanks!!!

killer medic · Oct 20, 2006

Just curious...

mustangdave · Oct 20, 2006

Post some casting numbers off the intake and other easy to read parts for a start. C8....... would be 1968, D7.... would be 1977, E5....would be 1985, etc.... 1985 was the start of the roller blocks.

D.Hearne · Oct 21, 2006

killer medic said:
Does that also apply to all electrical and vacuum applications? What about compression rations and cam information. If I were to plan on changing the head, cam, and intake, I guess it REALLY wouldn't matter since I have created a whole new configuration. I am just wondering if it is feasible to find out what I have to determine these configurations without tearing it apart (at least not yet). When I go to the auto part store and give the make and model of my car, of course there is no 302 option because it hadn't existed yet. If I told them it was a '68 mustang, would that be feasible, being the close similarities? BTW, how would I know if I don't have a Boss 302 configuration on my hands? I am really curious as hell to see if my engine in on the milder or wilder side. Thanks!!!

Pretty much all the base model 302, 2 bbl motors in all applications used the same bunch of parts, from the first 68 motors to the end of carbs. There were minor revisions over the years, but it was a one size fits all proposition, the same basic engine was used in cars, pickups & vans. If you had a Boss 302 you'd know it. This was a COMPLETELY different animal. Cleveland style heads, aluminum intake, 4 bolt main block with screw in freeze plugs, finned aluminum valve covers, Holley 780 carb, plus other stuff. All it really lacked for all out performance was headers.

killer medic · Oct 21, 2006

thanks for the education!

rear end difference

bertman

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1966conv

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mustangdave

My rearend needs a stud and two nuts.

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