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Discussion Starter #1
2003 GT
MM torque arm
MM PHB
Ford Racing Aluminum Drive Line

Finished installing my MM torque arm MMTA-1. I have set the pinion angle to match the angle at the crank pulley while at ride height. I also have fresh gear oil in the diff as I had to rework my cover.

I took the car out out for the first shake down drive. First few miles were fine. Made a few spirited starts, no issues. came to a point that I let it rip pretty good and all of a sudden I started getting bad noise in the drive line. I could swear it was coming from the front u-joint, almost like it was hitting the tunnel. It was so bad that I couldn't drive it back the three miles to my house. Once I got it towed back, I got it on the lift and did a visual. Nothing seems out of the ordinary and seems OK with hand rotation. I started the car and let it idle in 1st gear and its definitely still making noise. But I can not Isolate the problem. it is not hitting anywhere. I can't tell if I killed one of the u-joints (doesn't sound like the typical beginning of failure) or if they are binding under load with the new pinion angle. Most likely I think I killed one of the plenary gears? I just spun the rear tire by hand. They the opposite side spins in the opposite directions. I thought the LSD both spun in same direction?

Any thoughts on how to isolate / trouble shoot this?
 

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I always put a angle finder across the machined face areas of the yoke without the driveshaft attached, and matched the pinion like that.

As for the rear end with a limited slip... If you can turn the wheel by hand and the other side rotates, your clutches are toast. It is basically an open differential now.

Can you put it in neutral, on the lift, and turn the driveshaft by hand and feel for the issue? Probably the easiest thing would be to remove the driveshaft, and try turning the trans output shaft and the axle pinion yke by hand, see if you can feel it in either one. This would also let you manually manipulate the u-joints and feel for issues.
 

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Discussion Starter #3
I’ll be able to spend more time troubleshooting after work today. I’ll be able to be more methodical now that I’ve calmed down. The more I think about it, it’s probably the spider gears. Not sure why they would give up now though. No previous warning signs (NVH). Who knows. Maybe the removal of all the rubber isolators and locking the axel in a fixed position was too much direct torque for it to handle.
 

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I had no rear end issues after my T/A install. I did rebuild the clutch packs with new pieces, tightly packed but that was it. Also have an aluminum DS. Given what the wheels do when turned, I'd guess spiders.
 

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Discussion Starter #5
Well, it's confirmed. My LSD is now an open diff. I went out at lunch and checked the driveline. Looks good. Made my way back the rear end. Spun the tires listening for noise. Then I realize that I had left it in gear and the driveline wasn't moving but I could make the wheels spin... uh oh.

So, I'll pop the cover off and assess the damage later. Hopefully, I can get away with just new clutch packs and spider gears. I am concerned about metal contaminating the carrier bearings though.

Since I am doing the work anyway, I'll upgrade to 31 spline gears and axles.

Option 1, just do a clutch pack / gear rebuild.
Spider gears 31 spline - Ford - AL32-4215-A ~$90.00
Clutch pack, Carbon Disc - Ford - M-4799-C ~107.00
Total: $197

Option 2, replace the whole center section.
Traction-LOK Limited Slip Differential w/ Carbon Discs - Ford - M-4204-F318C ~$227
Differential Bearings - TBD - ~40 / set
Total: $267


31 Spline axles - Moser - A883153 ~$288.00
ABS reluctor ring(s) - Ford - F4ZZ-2C189-A ~$32.00 (x2) $64.00
Axle Bearings - TBD - ~$40 / set
Total: $392
 

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Discussion Starter #6
I always put a angle finder across the machined face areas of the yoke without the driveshaft attached, and matched the pinion like that.
Sounds reasonable. I just did it the way that MM suggested in the TA install instructions. Getting the driveshaft out of there now with the TA in is going to be a real pain.
 

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Did you feel anything odd when turning the wheels?

Spiders are only doing their job in turns or lack of traction. Going straight down the road they are not turning, so they wouldn't be making any NVH. Only way I can see it is if a tooth broke off and damaged the ring/pinion or bearings.

Sent from my VS995 using Tapatalk
 

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After installing TA in my car I had a bad vibration as well, especially north of 65 mph. Took the driveshaft, had it balanced (was way out) and now silky smooth. Solid mounting the rear made a previously masked issue come to light.

Sent from my Pixel using Tapatalk
 

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Discussion Starter #9
Did you feel anything odd when turning the wheels?

Spiders are only doing their job in turns or lack of traction. Going straight down the road they are not turning, so they wouldn't be making any NVH. Only way I can see it is if a tooth broke off and damaged the ring/pinion or bearings.

Sent from my VS995 using Tapatalk
Not especially. However, when I rotate the wheel there is about 0.5” of free backlash.

I don’t think it’s the driveshaft. It was fine at speed. The clunk, vibration, knocking I am experiencing after that fateful launch is immediate at low speed under any load.

Manually manipulating the driveshaft, it feels nice and tight. No clunk, nothing loose.
 

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Discussion Starter #10
Pulled the diff cover. Looks ok. However, the backlash is horrendous. I will go ahead and do the spiders and clutch packs.

So, with the car on the lift, drop it into gear, I can definitely tell it is in the front. Especially when I engage the clutch. I have rotated the driveshaft by hand and inspected the yoke. I don't have any unusual movement in the u-joint and I don't see any signs of in binding. Clutch seems to engage and disengage fine.

I am wondering if it is in the transmission? I suppose I can drain the trans and see if there is any debris in there. But is seems to go through the gears ok.

Could it be bad trans mount? Again, I don't see signs of hitting or binding.

I don't know. I am really grasping at straws now...

I need a second set of eyes and ears too...
 

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Discussion Starter #11
OK. I have to pull it all apart and get the driveshaft out. I know this is going to sound weird but I swear I hear the noise coming from almost dead center of it. Maybe a bad u-joint and the noise is traveling like on a tuning fork? I don't know. I am really perplexed by this one. At least its a good excuse to check out the u-joints and maybe upgrade while its out. The only other thing it can be is the output shaft of the TR3650 (or something else internal). Just wish I could nail down where the hell the noise is really coming from. Side note... clutch packs and spiders ordered...
 

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The TA is bolted to the axle housing. The nose of the TA is connected to the TA crossmember through the polyurethane bushing. THe TA crossmember is bolted to the subframe connectors in the middle of the car. This means that any driveline noises are now going to come from the middle of the car, no matter where they are actually present in the driveline.

In the TA installation instructions, it says to jam the TA crossmember against the bottom of the floorpan. This is a mistake. You should leave a small (1/8") gap between the top of the crossmember and the bottom of the floorpan. You will need to look carefully to find the spot where the clearance is closest. This will minimize sound conduction from the TA to the floorpan of the car.

Because the TA conducts driveline noises into the chassis efficiently, any problems with the driveline will be much more obvious.

If you change axles, I would use Yukons. They have good spline forming, correct hardening and accurate dimensions.

With the TA, at low speeds, avoid on/off throttle transitions. This will minimize clunking in the driveline. Either be on the throttle slightly (possibly with some brakes) or completely off the brakes. The more lash your driveline has, the more this will help.

I would put jack stands under the rear axle housing. Block the front tires. Have someone drive the car, while you go over all of the fixed driveline parts with a mechanics stethoscope. This will make it easy to find the source of the noise.
 

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Discussion Starter #13
In the TA installation instructions, it says to jam the TA crossmember against the bottom of the floorpan. This is a mistake. You should leave a small (1/8") gap between the top of the crossmember and the bottom of the floorpan. You will need to look carefully to find the spot where the clearance is closest. This will minimize sound conduction from the TA to the floorpan of the car.
Thanks for that tip. Fortunately, after much effort removing the interfering material from the seat belt anchors and beating the snot out of the tunnel, I ended up moving the crossmember down before welding in order to get the most weld area on the SFC's. Thus ended up with good crossmember to floor clearance.

I would put jack stands under the rear axle housing. Block the front tires. Have someone drive the car, while you go over all of the fixed driveline parts with a mechanics stethoscope. This will make it easy to find the source of the noise.
I have the car at ride height just barely off of the lift and sitting on four stands. I have been poking around with my stethoscope while it idles in gear. I just need to do this with someone on the throttle.

I'll continue troubleshooting and report back on the saga.
 

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Discussion Starter #14
It appears to be in the transmission. Seems to be the forward side of the gearbox but can't really isolate it. I don't hear grinding in the trans with my stethoscope. Not sure what to think. I'll pull the driveshaft and see if that helps to isolate. Clutch operation is fine. I don't hear any tale tell signs from the throw out bearing. I'll dump the oil to see if there are any fragments. As far as I know, the transmission is original with ~160k on it. Had no warning signs of trouble before this.

Here is an audio clip (it's long). You can really hear it clunk and grind with the clutch out. You can also hear it as it idles in gear.
 

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That sounds pretty sick!! Almost like a tooth missing on a gear in the transmission.
Good luck with it, but it has to be something major!!
 

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Discussion Starter #17
Complete T56 sourced. Spider gears, clutch packs, axles, ordered. Also ordered the M-2300-M adapter kit and calipers to upgrade the rear brakes to 11.65" (doing Brembo's upfront). Lots of work ahead.
 

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Discussion Starter #19
I know. I hear you.

But the transmission is toast. I know I could pick up a junkyard special for about $500. But I don't want to go that route. I'd just be buying the uncertainty that I had before. I did some pricing on a reputable good rebuild. It was going to end up costing me ~$1800 including the core shipping. It would be an extra $500 to get the 5th gear 0.81 ratio conversion. The T-56 I picked up has about 54k on it. Includes everything from the flywheel to driveshaft. I think it was an equitable decision.
 
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