Diff parts recommendations for 95 GT

Bitza

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Hi all,

95 GT, AODE, 2.73 Diff, 90,000km (55k miles)

I've got a vibration in the car that I have pretty much narrowed down to the diff. Plus there is a deep whine back there too.

Symptom:
is a vibration that enters AND exits at 50, and then 70 kmph. Yes the car is a Japanese export version, so in mph it's about 30 and 45 mph.

What I have done so far:
Driveshaft, harmonic balancer deleted, new uni joints fitted and then dynamically balanced.
Replaced all the suspension bushes, saddles etc with Energy Suspension gear, (they were showing their age).
Replaced all the std springs and stuffed shocks with an Eibach sports-plus springs and pro-damper shocks.
Removed the dogbone, which has reduced the severity of the vibrations.

My conclusion:
The vibration is definitely coming from the rear, as sometimes it is fair, then after a corner it is worse, (seems to be synchronized a little with the position of the wheels relative to each other).
There is no vibration thru the steering wheel, which would point more to engine or trans mounts.

So looking at doing a diff rebuild, and am after recommendations for 28 spline axle brand, new ratio/brand and rebuild kit brand. Looking at 3.27 or 3.55 ratio, heart tends to 3.55.

I have an account with rockauto (onya site sponsor!!!) And have previously purchased thru Summit.

So what do you guys think I should go for?

Cheers.
 

Silver95bird

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No mention of wheels and tires. this is probably the first thing to look into. are they stock wheels and good name brand tires with a decent speed rating? try different wheels/tires on different corners and see if it moves with the rotation. you may find the tires have to be knocked off the bead and rotated *180. sadly nobody pays attention to the indexing marks when mounting them, and then the stickers wear off, so you cant figure out where they were supposed to go. if you have any corners with a painted dot on the end of the stud, align it with the valve stem.

check all 4 wheels for play from the wheel bearings. if you work on the rear, make sure the bearings didnt wear a groove into the axleshafts.

check all engine and trans mounts. rubber can sometimes be more forgiving than polyurethane.
check the slip yoke and see if the bushing is worn out. there shouldn't be a ton of play in it, and the yoke should slide far enough in just like the OE. if the driveshaft is shorter than the stock one, the slip yoke won't go in as far. if using the stock yoke, dont remove the damper, and if it breaks, get a replacement with one.

best bet is to buy ford racing gears. i prefer the ford trak-lok rebuild kit as well, rebuilt in the stock way but with the thickest shim it comes with. 3.55 i think is great for a driver with a 5 spd. i might be in the minority on that, but i drive a lot on the highway with my 3.73s and i don't care for that, or the uselessness of 1st gear. Either or (3.27, 3.55) is a great upgrade to a 2.73.
 
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Bitza

Bitza

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Thanks for your answer Silver95bird.

You raised some good questions and got me thinking, so here could be some answers for you.

Out of interest I'm an aircraft engineer, so have very few fears of doing things myself, so far the only thing I have not done to the car myself is the driveshaft balancing. And there has been a fair bit done to bring her up to my standard.


Wheels and tyres, 4 totally different sets have been on the car since I bought it in Nov last year. See the photos below, in chronological order.20181130_195740.jpg 19 inch advanti rims on dunlop tyres, on the car for 100 miles

20181201_182318.jpg 17 inch (2001 mustang) on worn Goodyears, on the car for about 350 miles

FB_IMG_1550489082497.jpg 17 inch (1996 Mustang) with Bridgestones, did I guess 600 odd miles on them.

20190617_172331.jpg
Currently 18 inch DTM Atoms with Nankang NS2R, again with about 600 miles so far.

All the same vibration, no effect with any of the changes, so I have ruled tyres and wheels out.

The driveshaft is the original, it has has the harmonic balancer removed from the original yoke (as the rubber had hardened, cracked and the ring was offset), the uni joints replaced and then dynamically balanced. I have been looking for a replacement yoke with harmonic balancer on the Summit and Rockauto sites but they dont stock them, maybe Jeggs?

There is a little bit of play in the yoke bushing, but not enough to cause that sort of vibration from the rear of the car,( it should be felt at the front as well) but I'll replace it anyway.

The engine or tranny mount, if they were worn I would expect to feel a vibration through the front foot well and steering and less through the rear, again I will replace those anyway.

Must admit the diff rebuild cost could be a problem, it's a good distance to ship stuff to New Zealand.

Again, many thanks.
 

white95

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Here’s something simple to try. “Re-clock the driveshaft.” Disconnect the driveshaft from the rear end, rotate the driveshaft 45 degrees and then reconnect it.
 

RAU03MACH

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Hopefully you find it
Had to once replace a friend's driver side axle
Shaft it was bowed to where it felt like it was bouncing even when turning
 
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Bitza

Bitza

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Cheers for the replies guys.

Well I have picked up a replacement diff today. It came out of a 95 as well and I have been told it has only done about 35k. I'm going to strip it down tomorrow and get it to my diff guy to replace the ring and pinion and inner bearings. I'll do the rest myself.

Still undecided on the ratio. The car has a 2.73 at the moment, and the replacement has the same ratio. 1500 revs at 60mph, uses more fuel than when shes up around the 1800-2000 revs.

Any recommendations on 3.27 or 3.55?
 

evilcw311

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Are you concerned more about mpg or performance??


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Bitza

Bitza

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evilcw311, thanks for replying.

With the car running 2.73 at the moment I have pretty much neither.

At the moment,

2.73 @ 60mph is 1500 rpm

I've worked out that.

3.27 @ 60mph will give me 1800rpm
3.55 @ 60mph will give me 1950rpm

I have noticed an increase in fuel economy (I guess the engine is breathing better, call it optimal flow) within the 1800-2000rpm range, and of course changing the ratio to either 3.27 or 3.55 will help with the sluggish acceleration.

Down here in NZ we pay about $5.00 US per US gallon, so any increase in economy would be good too.

Plans for the engine are to get up around the 360hp mark, with some shorty headers, possible upgrade from the Trickflow exhaust, E303 cam, Y303 heads, explorer inlet manifold, 65mm tb and 70mm Maf.

Cheers.
 

evilcw311

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evilcw311, thanks for replying.

With the car running 2.73 at the moment I have pretty much neither.

At the moment,

2.73 @ 60mph is 1500 rpm

I've worked out that.

3.27 @ 60mph will give me 1800rpm
3.55 @ 60mph will give me 1950rpm

I have noticed an increase in fuel economy (I guess the engine is breathing better, call it optimal flow) within the 1800-2000rpm range, and of course changing the ratio to either 3.27 or 3.55 will help with the sluggish acceleration.

Down here in NZ we pay about $5.00 US per US gallon, so any increase in economy would be good too.

Plans for the engine are to get up around the 360hp mark, with some shorty headers, possible upgrade from the Trickflow exhaust, E303 cam, Y303 heads, explorer inlet manifold, 65mm tb and 70mm Maf.

Cheers.

If your worried about mpg then leave your gears alone. If your not worried about the mpg then step it up to either 3:73 or 4:10. The Auto’s wake up a lot more with the steeper gears.


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