Triumph Repair: trasmission noise, triumph gt6, electric overdrive

Question
QUESTION: 1970 Triumph GT6 + with electric overdrive, in reverse, let out the clutch, get a very loud noise?

ANSWER: Dale,

In my autocross Spitfire I get a loud noise in every gear when I let out the clutch.  Tire squeal and exhaust noise.

I guess you're saying it happens only in reverse?

Is it a big BANG noise?  Or a CLUNK?  Or a grinding sound?   Or?  Or?

You can't run the transmission in reverse with the o/d engaged or it'll destroy the unidirectional clutch.  Then again, it only happens once then the o/d is destroyed.   So, I don't think that's it.

How about some more details in the description?  


Cheers,

Jim

---------- FOLLOW-UP ----------

QUESTION: 1970 Triumph GT6 +, Transmission with overdrive, in reverse, let out the clutch, get very, very loud winnig noise. This is not the typical reverse wine sound from most British cars, it is extremely amplified. Also, in first gear, let out the clutch, car gets moving, after about 10-20 feet it feels like the clutch is releasing for a second time. I have owed this car for a very long time and have never had these typse of problems happen all of a sudden. Thank you for any insight you might be able to offer.

Answer
Dale,

When was the last time you checked the transmission oil level?   The reverse gear teeth are straight cut and will be noisier than the forward gears normally.   When it gets really loud it's saying that the clearance between the gears has changed or the teeth are meshing dry, or both.   

And the "second clutch" effect in first sounds like the overdrive is engaging.  From the factory the overdrive was only set up to work on the upper gears (usually 3-4 or sometimes 2-3-4).  The overdrive pump is operated by a cam on the tailshaft, and when you're just starting out there's no pressure in the system and you'll be in direct drive (no o/d effect).  Once the pressure builds it's popping into o/d.

At least, that's what it sounds like from here.


Cheers,

Jim