Diagnose my rear end

[Redline]

The rear end of my '71 Coupe, that is. It probably needs some work:

1. It makes a light PLINK! when changing between reverse and first
2. It's a bit rumbly at 60 kph
3. It's rather more rumbly / shaky above 120 kph
4. It's generally noisy on the power and on deceleration, but silent and the load is transitioning between the two (i.e I can provoke noise or silence coming on and off the gas on the motorway).

The driveshaft was balanced about 10'000km ago.

So far it's not critical, but it does detract from the fun as there is no joy going above 110 kph (70 mph) and the little 1608 would be more than willing.

I guess this all points towards the differential?

[Fi8spider]

Hey there Redline, check guibo carefully and universal joints before pulling anything apart, I'd also be eyeing over the center bearing support.
My 124 was doing the same thing as you explained and after replacing these items (which were in a bad state) along with a fresh gearbox mount the rumble went away. Not sure about the plinking problem but if it showed up the same time as the rumble then the chances are that they could be related.

[Redline]

Thanks. The U-joints, center bearing and guibo were all replaced when the driveshaft was balanced.

[Fi8spider]

Knowing your attention to detail Redline I didn't think for a moment that you hadn't changed those parts. It would still be worth checking.

[76was124]

You might want to re-word your post title though

[azruss]

my 71 tranny had that same clunk between 1st and reverse, like there is too much play. It has been that way since the tranny was new, some 300k miles ago. I was told at that time that it was because the gears weren't "leaded".

[Redline]

You might want to re-word your post title though

No sense of humour?

[vandor]

You'd need a driveine shop diagnose the rear end, but with all those symptoms it sounds like it needs a rebuild. The clunk cold be worn spider gears. The noise could be the bearings. If you drive it like this too long the gears may not be reusable either.

[Redline]

Over here, NOS 124 diffs are only about $360, which doesn't buy you much bench time here, so if it needs a rebuild I would probably just go with slotting in a new one. I'll have it looked at in the spring then. In the meantime I can put it up on stands and look at the guibo, center bearing etc. Thanks for the feedback.

[76was124]

You might want to re-word your post title though

No sense of humour?

Ha, I got it, I wasn't sure anyone else did!

[spiderdan]

You might want to re-word your post title though

No sense of humour?

Ha, I got it, I wasn't sure anyone else did!

I wasn't going to touch it...
Unless I was in a Ford "Probe"

[djape1977]

check rear wheel bearings

[fiatfactory]

.