1970 1600, hearing some noise from the back end.

[mspencer]

it's a daily driver, but since I heard this noise, I have stopped driving it. I think it's the drive shaft joints... or something loose like the exhaust. I jacked up the back end and I do see oil coming from the front of the Diff. I have not worked with these before so I assume the leak is from the front seal. Not sure what else I should be getting while I am replacing it and if there are any best practices on how to replace it. I will pull the fill plug and see how much oil was lost as I am not sure if this was my original nose issue or not. Any guidance here is much appreciated.

[redroadster68]

Is the noise more prominent on deceleration or acceleration? Is there a clunking sound ? Is the a constant whine ? All these “ maybe” an indication of “possible” differential issues…pinion etc. lots of good articles online and on here .. hope it’s something simple.
FYI. 80w90 gear oil will do ya.

[Gregs672000]

Out of my area of expertise, but I would think that if you grabbed ahold of the drive shaft and wiggled it you would see any problems with the u joints. Regarding the seal, I defer to more experienced folks...

[mspencer]

Thanks, yes gave the drive line a quick check, no wiggle at all so that looks good.

[redroadster]

Look closely at each bearing cap on the U joints to see if any show rust
The seals mostly would leak some , and not be a major leak / problem but
who knows how it was driven ...if
It set for yrs the out of fluid part of the diff can rust and
the seal replace is a bit tricky you want to mark the flange nut position
With white touch up type paint let it dry good , we used a impact gun
to break start the nut off ,pry the seal out and replace going back stop just short of the aligning marks you made
You can drain the diff replace with lear hydrolic oil ,drive 20miles drain to see debrie

[C.Costine]

A noise from the rear axle is most likely a wheel bearing which is usually a whine but it is at the end of the axle not at the differential. Gear oil leaking means a leaking pinion seal, so that is an issue, but it may not be related to the noise. Our roadsters are notorious for exhaust hanger noises, which sound like a hum, and the most likely spot is where the pipe goes through the frame.

[FergO2k]

Amen to that exhaust hanger nagging noise. The "flex pipe" offered by vendors solves this, as then the exhaust can be hard mounted all the way back, and the wiggling engine (our stock engine mounts are very soft, comparatively) can do its thing without all the noise.