I think I have something going on with the differential

[tony-muscle]

There is a noise coming from the rear end that has gotten worse. I turn the wheels by hand in my garage but don't hear anything. I had a statoscope on the pinion bearing and axle bearings and can't hear anything when turning by hand. Next I will start the car on the lift and turn the wheels to see if I can replicate it. The noise starts at about 20 mph and it is very constant during acceleration or deceleration, turning one way or the other. I don't think it is an axle bearing. I thought the likely suspect will be a pinion bearing. I got my third member assemble with a Truetrac from Strange and it only has about 10,000 miles on it so that sucks. Oil is just below the fill port - maybe 1/4" below. Whatever is going on, I will do some more troubleshooting but it looks like the third member is coming out. I will then take it to a shop.

 

[Doug's 73 Mach1]

Drive shaft universal joint(s) could be a possibility also.

 

[tony-muscle]

Drive shaft universal joint(s) could be a possibility also.

I was thinking about those, but I was not expecting them to sound like this. Mine are sealed 1350s and were installed at the same time as the third member, about 10,000 miles. Is there a way to diagnose them. I guess I can check for play, but is there anything else?

 

[Tnfastbk]

Any vibrations or just noise? If just noise I would lean to rear end as well

 

[Hemikiller]

Put the car on a lift and have a helper bring it up to the speed where you can hear it in the car. If it's audible in the car, you'll definitely hear it under it. The stethescope is your friend here. I'd be pretty happy with 10k if you drive the car as hard as I think you do.

 

[tony-muscle]

Put the car on a lift and have a helper bring it up to the speed where you can hear it in the car. If it's audible in the car, you'll definitely hear it under it. The stethescope is your friend here. I'd be pretty happy with 10k if you drive the car as hard as I think you do.

That's the plan. Interesting to hear that you will be happy with 10k miles of hard driving. I didn't think much of it but maybe AutoX is too much for a Truetrac.

 

[tony-muscle]

I went under the car while on jack stands. Definitely can hear the noise past 20 mph but not sure from where. I was on the back with the statoscope and there is noise coming from everywhere so now I don't know if what I hear with the statoscope is normal or not. The more suspect noise actually came from the transmission tail shaft. I have a TKO600 that I got new the same 10k miles ago. However, I feel I am not completely sure. The oil level on the transmission is right at the fill port. There is no oil leakage on the tail shaft. If I move the driveshaft up and down by the transmission there is a little slop. Will this be normal?

 

[Cleveland Crush]

Tony,
Rear ends make lots of noise when running especially thru a stethoscope. Some slop is normal and necessary at the drive shaft slip joint/tranny output shaft in order to function properly. 1350 ujoints can take huge punishment EXCEPT for poor driveline angle which can do them in quickly, verify your shaft angles are in spec. Consider pulling the drive shaft and checking the ujoints by hand for tightness and smoothness. Thing is the driveshaft magnifies noise from the tranny back and/or from the rear end forward, with that said I'd verify ujoint condition first along with driveline angle, then go from there.
You previously posted about a snapped clutch cable bracket, maybe related some how?
Just throwing a few thoughts out there since I run the pretty much the same driveline as you.

 

[Doug's 73 Mach1]

I would expect no slop. If there is slop, the drive shaft assembly at that end could move off center and vibrate when spinning. The drive shaft assembly might be out of balance. The severity of vibration (and resulting noise) would tend to change at different rpms, more sever at speeds near the "natural frequency" of an out of balance rotating part. Similar to what you feel with an out of balance tire/wheel, more vibration at certain speeds than others.

 

[Cleveland Crush]

Tony, just as a reference measurement for your tko output shaft "slop" (freeplay is probably a better term) my two different tko tranny output shafts measure .08" and .010" freeplay respectively. As for driveline angle this diagram has always worked for me:

 

[tony-muscle]

Tony, just as a reference measurement for your tko output shaft "slop" (freeplay is probably a better term) my two different tko tranny output shafts measure .08" and .010" freeplay respectively. As for driveline angle this diagram has always worked for me:
View attachment 78779

Thank you. I checked all the angles when I installed mine. The u-joints looked very good and definitely not making the noise. Today or tomorrow will check again to see what I can find or confirm.

 

[Sheriff41]

Might be worthwhile to change the oil in the diff so you can check for debris. If your pinion bearings or carrier bearings are going bad you'll see metal in the oil. At best, you'll have fresh gear oil; at worst, you'll have to clean everything and replace bearings.

 

[giantpune]

Tony, just as a reference measurement for your tko output shaft "slop" (freeplay is probably a better term) my two different tko tranny output shafts measure .08" and .010" freeplay respectively. As for driveline angle this diagram has always worked for me:
View attachment 78779

I think depending on how hard the car will be driven, you dont want the input and output shafts parallel when the car is at rest. When you are hard on the throttle, the rear axle housing will rotate a couple degrees. If the car spends a bunch of time under hard acceleration, it may be preferable to have the input and output shafts mismatched a couple degrees. That way when you are really running the thing, the movement of the rear axle pulls the 2 universal joints into being parallel with each other.

And as far as OP running autoX, I think this is part of the hobby. Auto sports is hard on parts. I'm not surprised at all to hear that a car with 10k miles and doing autoX is breaking stuff. A lot of the power sports performance parts have service intervals and lifetimes measured in like tens of hours, which translates to like 100-200 miles.

There's a great video of an F1 driver taking a normal BMW on a race track and driving the snot out of it. The aftermath video showed that within like 40 laps (450 miles), several of the components were toast. Even the wheel bearings, which would have lasted 150k miles of normal driving were gone from 450 miles of hard driving.

 

[tony-muscle]

Might be worthwhile to change the oil in the diff so you can check for debris. If your pinion bearings or carrier bearings are going bad you'll see metal in the oil. At best, you'll have fresh gear oil; at worst, you'll have to clean everything and replace bearings.

Totally. I agree. This is the easiest step before dealing with the transmission.

 

[Kilgon]

If you pull the drive shaft you will be able to check the u-joints, rear end and tranny and tail shaft independent of each other to track the problem down. You check to see if the u joints are moving freely and smooth. The rear end can be checked by using a variable speed electric drill to drive it. Most battery operated don't have enough torque at high rpm. Not for sure of you tire size, but with your 3.50 gear any drill that will reach about 1,000 rpm should get you up to the 20mph range. You can also check the tranny output shaft to see how much slop there is.

 

[tony-muscle]

I will have an update tomorrow since I will work on taking out the 3rd member in the morning. I don't think my issue is a u-joint but I will definitely double check them. I honestly hope the issue is with the differential and not the transmission.

 

[tony-muscle]

Update:
I have sealed outer bearings. Both are broken and wobbly. The differential looks all god and the oil is clean. So I think there is a good chance that 's the culprit, which is the best case scenario. Now i want to understand why they cracked so quickly. Are the sealed ones weaker than the normal ones? My bearings are from Strange so i will give them a call Monday.

 

[Bentworker]

Update:
I have sealed outer bearings. Both are broken and wobbly. The differential looks all god and the oil is clean. So I think there is a good chance that 's the culprit, which is the best case scenario. Now i want to understand why they cracked so quickly. Are the sealed ones weaker than the normal ones? My bearings are from Strange so i will give them a call Monday.

I wonder if your endplay was out of whack. When you reassemble with new bearings be sure to measure endplay. I had to scrape every bit of powder coating off the mating surfaces of my axle housing and brake caliper brackets to get it in spec.

 

[Cleveland Crush]

Our Mustang housing bearings are the "Small" diameter. The Torino's and up used the larger/stronger diameter bearing. After market 31 spline axles use a hybrid bearing that helps a bit (looks like you have the hybrid bearings). I've been through your bearing delema a few times. Good to see no serious damage done!

 

[tony-muscle]

I wonder if your endplay was out of whack. When you reassemble with new bearings be sure to measure endplay. I had to scrape every bit of powder coating off the mating surfaces of my axle housing and brake caliper brackets to get it in spec.

Can you please explain about the end play?