New to me 86 Mustang GT

86Stang50 · May 27, 2011

Just picked this Mustang up. I'm a car guy but have no experience with fords. 86 GT with a 91 5.0 swapped in. 3:73 gears in the rear. The engine runs very well, and even sounds like it may be cammed. Now, when shifting through the gears, getting into 3rd and up the rear end(sounds like it) starts to whine very loudly up until 55 or so, ONLY when on the gas. After about 85 it develops a vibration in the driveline which seems pretty severe. The car is in excellent shape and all seems well underneath, U joints, trans fluid, etc. Have yet to check the rear diff fluid. Could it be that the spacing between the pinion gears is off? Or do aftermarket gears usually make noise? Thanks

f8tlfiveo · May 28, 2011

Aftermarket gears sometimes cause a vibration because the driveshaft has to spin faster.. Most people replace stock shaft with an aluminum one..

2000xp8 · May 28, 2011

The aftermarket gears aren't what causes the vibration or whining, it's the guy who put them in that caused it.

The vibration itself is probably the driveshaft, as jeep said, get an aluminum driveshaft.

For the rear if it's been whining a while (for you or the previous owner) i'd just do new gears and all new bearings, once a pattern is thoroughly worn into gears it may be tough to get the whining to stop. Sometimes it can be fixed but if the history of the rear is unknown it may just be good precaution to buy new gears instead of doing it twice.

86Stang50 · May 30, 2011

Well i pulled off the cover, and the gears are indeed 3:73 by Ford. They look in great condition with no wear. But it doesn't seem like there is any backlash between them. Filled with new oil and some gear lube additive and it got quieter, but still somewhat loud.

86Stang50 · May 30, 2011

Also the car has a oil leak which appears to be coming from the rear main seal. When i had it up on the lift there was also oil running down the sides of the trans/engine and onto the exhaust (i assume reason for it smoking when you really get on the gas) Could it be the back of the intake or valve cover gaskets leaking? If it was the rear main seal, would it throw oil slightly up and to the sides of the engine or just drip out of the bottom where it meets the bell housing? Thanks.

LX302 · May 31, 2011

Valve cover gaskets are always the culprit of leaking onto the headers, check by the spark plug to see how wet it is. Besides the rear main, the other area to watch is the back of the lower intake.

NIKwoaC · May 31, 2011

That's a good looking car! I have never seen those wheels before, I kind of like them. Do you know what they are?

Also, have you had the wheels balanced? Sometimes high speed vibration can be as simple as poorly balanced wheels or wheels that have not been balanced at all.

VibrantRedGT · May 31, 2011

Could be the balancer causing the vibration and if so it could do damage so check that first. I had severe vibration under load after 65MPH and luckily it was the driveshaft and just put in a FRPP aluminum (light weight too) and vibration was gone forever.

Those rims are aftermarket and from the early 90's. Those use to be real popular 20 years ago. Always loved the 4 headlight FOX body. The best rims to put on that car are the 91-93 Pony rims. Even better in chrome.

Noobz347 · May 31, 2011

How loud is the whining?

If it's a ruibuilt or super-duty/remanufactured T5 with the kevlar synchros then it will whine. I have those synchros and it whines (like a centri-supercharger) when I'm hard on the gas.

The vibration... as I see it, is your only current problem. Balance the wheels, replace the U-joints, and check the driveshaft to see if it's true and balanced.

If the vibration is cured and you still hear the whine under accel then press on with life.

If the vibration is cured and you can't hear the whine anymore, then I was wrong about you having kevlar synchros.

Either way, you'd be good to go.

86Stang50 · May 31, 2011

Those wheels are made by ROH. 16". I like them too.

The whine is moderate. Got quieter when i replaced the gear oil. Increases with speed and then stops around 55.

Is that aerostar shaft swap a good option?

Also, it is not oily next to and behind the valve covers. The oil seems to be dripping onto the exhaust right after the down pipe. There is some oil and dirt behind the intake/top on bell housing. It is hard to pinpoint the leak when you cant see back there.

*Traction is also an issue. I cant even get on the gas around corners in second without breaking loose. Yeah, it is fun, until you end up in the ditch and have a 90$ towing fee. Don't ask me how i know. Anything to help with that??

2000xp8 · May 31, 2011

86Stang50 said:
Those wheels are made by ROH. 16". I like them too.

The whine is moderate. Got quieter when i replaced the gear oil. Increases with speed and then stops around 55.

Is that aerostar shaft swap a good option?

Also, it is not oily next to and behind the valve covers. The oil seems to be dripping onto the exhaust right after the down pipe. There is some oil and dirt behind the intake/top on bell housing. It is hard to pinpoint the leak when you cant see back there.

*Traction is also an issue. I cant even get on the gas around corners in second without breaking loose. Yeah, it is fun, until you end up in the ditch and have a 90$ towing fee. Don't ask me how i know. Anything to help with that??

Dont' know how successful people have actually been with the aerostar driveshaft, but me personally that's a part i like NIB. I know it's expensive, but it's worth every dime.

Traction, get better tires.
The lower the treadwear rating, the better the traction is.
I believe drag radials are 000.
Not sure how you use the car, but if doesn't see a ton of miles, drag radials for sure.

NIKwoaC · Jun 1, 2011

Every single Aerostar I was ever able to find in junk yards had a crushed driveshaft from being carelessly moved with a fork lift. You can look for one, but good luck finding one in good shape! It would definitely save you some money.

Traction issues? Easy fix. Use less right foot.

2000xp8 · Jun 1, 2011

NikwoaC said:
Every single Aerostar I was ever able to find in junk yards had a crushed driveshaft from being carelessly moved with a fork lift. You can look for one, but good luck finding one in good shape! It would definitely save you some money.

Traction issues? Easy fix. Use less right foot.

That's why i don't like the junkyard driveshaft idea. The driveshaft is so easily unbalanced by banging it around, then add the cost of new ford U joints IMO it isn't even worth the risk. You could be in something $150 and it may vibrate.

86Stang50 · Jun 1, 2011

Ill just have to get this thing fixed up piece by piece. Not much $$ to play around with. Its my daily driver next to the motorcycles.

Seems like oil is pooling up behind the intake manifold. Hopefully that is just leaking and not the rear main. Probably replace it this weekend.

michaelg10 · Jun 1, 2011

I had the same issue on my 86GT. Ended up swapping in another 8.8 and replacing the u joints.

jrichker · Jun 1, 2011

Aluminum driveshaft: (courtesy of shawn13) It needs to be from a 92-93-94 Aerostar AWD. It measures 45 ½” center of the front U-joint to center of the rear U-joint. You will need the U-joint, part #PUJ353 from NAPA. The Canadian NAPA pat number is 1-0134BF. It should bolt right up after the U-joint swap.

Note: This driveshaft is not an exact duplicate of the Ford Racing part. It is 3” in diameter while the Ford Racing part is 3.5” in diameter. There is no guarantee that the balance will be any better than the stock part.

Use a piece of string and wrap it around the driveshaft. Make a mark on the string where the ends overlap. Measure the length of the string:
On the 3" AeroStar driveshaft the string will be 9.42" or about 9 7/16" long.
On the Ford Racing 3.5" driveshaft the string will be 10.99" or about 11" long

NIKwoaC · Jun 1, 2011

jrichker said:
Aluminum driveshaft: (courtesy of shawn13) It needs to be from a 92-93-94 Aerostar AWD. It measures 45 ½” center of the front U-joint to center of the rear U-joint. You will need the U-joint, part #PUJ353 from NAPA. The Canadian NAPA pat number is 1-0134BF. It should bolt right up after the U-joint swap.

Note: This driveshaft is not an exact duplicate of the Ford Racing part. It is 3” in diameter while the Ford Racing part is 3.5” in diameter. There is no guarantee that the balance will be any better than the stock part.

Use a piece of string and wrap it around the driveshaft. Make a mark on the string where the ends overlap. Measure the length of the string:
On the 3" AeroStar driveshaft the string will be 9.42" or about 9 7/16" long.
On the Ford Racing 3.5" driveshaft the string will be 10.99" or about 11" long

Weird. I did not know the Aerostar driveshafts were any different. Learn something new every day!

2000xp8 · Jun 2, 2011

86Stang50 said:
Ill just have to get this thing fixed up piece by piece. Not much $$ to play around with. Its my daily driver next to the motorcycles.

Seems like oil is pooling up behind the intake manifold. Hopefully that is just leaking and not the rear main. Probably replace it this weekend.

Since money is an object here, get yourself 2 new FORD u joints, buy them at ford, no at autozone.
For the oil, make sure you have the good hard rubber valve cover gaskets, the cork ones are worthless.

86Stang50 · Jun 2, 2011

Picked up the gaskets for the intake. Looks like felpro updated their kit as they come with rubber seals for the front and back now instead of cork(form what ive read people have had problems with the cork ones)

Should be a pretty quick job. I shouldnt have to remove the dist. correct?

2000xp8 · Jun 2, 2011

86Stang50 said:
Picked up the gaskets for the intake. Looks like felpro updated their kit as they come with rubber seals for the front and back now instead of cork(form what ive read people have had problems with the cork ones)

Should be a pretty quick job. I shouldnt have to remove the dist. correct?

Been a while since i remove a 5.0 intake, but you may have to turn it to get passed the module.
If so, just mark it where it sits, then loosen and turn.

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