Smoke pouring out of tranny

[analogmike]

This 2018 winter in New England we didn't have the usual clean-road days, so I did not get to exercise my '74. I finally drove it a few weeks ago and noticed the clutch slipping a bit on launches. When I got home I sprayed some brakeclean into the hole in the bell housing to see if that might get rid of some oil. Clutch cable adjustment seems ok.

The next week I drove 5 miles to work, went ok.
On the way home, at a steady 35 mph, I may have felt or heard something, looked back and there was a lot of smoke... it was coming out of the hole in the bell housing. Smells like engine oil, not tranny oil. No oil leaking out to the ground.

I let it cool down a bit then drove home, mostly coasting with the engine off (poor steering lock design, need to have electronics ON to avoid locking).
It made it back ok and still no leaks.

I am guessing oil got on the clutch due to a dried out seal. But I don't know why it smoked so much, I don't think it was slipping and the trans does not get hot enough to generate smoke. Someone mentioned a rats nest in there could cause that but it didn't smell like that. I have used brakeclean to clean my Porsche's clutches for years with no issues.

Has anyone had this happen before? I guess I have to pull the tranny but not sure what parts I should order.

[LotusJoe]

My guess is clutch smoke.

[jbcollier]

Sounds like a slipping clutch.  Regardless, it will have to come apart to see what’s up.

Why are you spraying your clutches with brake clean?  Any engine oil will leak out the bottom, not onto the clutch.  Gear box oil leaks can a problem but not one that brake clean will solve.  There is a small amount of lube on the clutch splines and in the input shaft support bearing/bushing.  Brake clean may wash that lube out which May lead to spline wear and/or bushing/bearing failure.

[Gmg31]

Please feel free to shout NOOOOO if my colleagues on the group disagree but many moons ago I was helping out in a pit crew at a rally and a similar thing happened.  The crew chief squirted coca cola into the bell housing and it seemed to fix the problem and we didn't need to replace the clutch during the rally.  It may be old nonsense but I'm sure our friends on here will have view.

[Roger]

I've heard of all kinds of remedies for slipping clutches. Fuller's Earth is my favourite.

Back to the original issue. Smoke pouring out suggests the clutch is slipping a lot, as if it were not completely engaged.
Other possibilities include seizing thrust bearing. In any case,  order new driven and pressure plate assemblies, new thrust bearing and replace.

[jbcollier]

You can do all sorts of things to get a car to work for a short period of time.  I’m sure the crew chief didn’t think he was performing a long term fix.

[analogmike]

Thanks for the replies, I was hoping this was not unusual on these cars. I guess I'll have to pull it apart. I have a broken finger so I can't work on cars for a while ;(

Maybe time to bring it to a shop...

thanks!

[LotusJoe]

Please feel free to shout NOOOOO if my colleagues on the group disagree but many moons ago I was helping out in a pit crew at a rally and a similar thing happened.  The crew chief squirted coca cola into the bell housing and it seemed to fix the problem and we didn't need to replace the clutch during the rally.  It may be old nonsense but I'm sure our friends on here will have view.

Actually I have used vinegar with good success.

[analogmike]

I just wanted to post the outcome of this, it was a seized throwout bearing causing the smoke. When changing it, the bell housing was found to be cracked so it needed repair, but it's working fine now.

[BDA]

Glad you got it fixed! 

I hope it didn’t take three years to fix it!

[Bainford]

Thanks for the update. I was curious about that problem. Glad you got it all sorted.