C3 Race Car Build

[Nassau65]

Makes it go faster.

 

[GCorvette]

Makes it go faster.

Go Throttle Open!

 

[Oneball]

That was quick! What is the GTO sticker for?

Wasn’t that bad to be honest.
The GT class in IMSA was split into Up to 3 litres and Over 3 litres. GTO

 

[Oneball]

Still none the wiser

 

[Alexm]

What about wear on the selector arms ?

 

[Oneball]

What about wear on the selector arms ?

They’re new too.

The one thing I have noticed is the part number of the synchro hubs to go with the sliders is different in the manufacturers catalogue to the ones they supplied as a set so I’ve sent them an email

 

[Alexm]

Rebuilt my 73 4 speed with a kit from a reputable us company, kept jumping out of second on overrun
Couldn’t suss the problem myself had in in and out the car twice before I spoke to Steve at dart (who I used to buy most of my parts from and get amazing amounts of advice from)
They looked at it and found one of the selector arms hadn’t been machined correctly,
Sadly this knowledge store is no longer available
A big loss to people who want to work on their cars themselves.

 

[Oneball]

I’ve put it into 3rd and the removed the side cover to check it’s engaging all the way. I’ve also looked at the wear on the new forks and they’re the same all 4 sides so I think that selector mechanism is ok. The combs look good but I might just replace them for peace of mind.

 

[antijam]

What a PITA - it would have been more satisfying if you'd found something obviously awry that explained the problem.

 

[Oneball]

Company got back to me and they’ve updated their catalogue so nothing wrong there. They’ve recommend I change the shift combs and put a stronger spring on them.

 

[johng]

let's hope that does it, presumably there's no way to check without refitting the box.

 

[Nick B]

Fingers crossed for you Tim.

 

[Oneball]

let's hope that does it, presumably there's no way to check without refitting the box.

Not really as I can’t actually find anything wrong.

 

[Oneball]

While the box is out I’ve put some reflective material on the floor pans and tunnel to try and keep it a bit cooler inside.

 

[Oneball]

Box back together, with new selector combs and spring.

 

[Oneball]

Still pops out of 3rd gear. Bugger

 

[Nick B]

Still pops out of 3rd gear. Bugger

 

[Oneball]

I’m thinking spigot bearing. Perhaps there’s more than one as it’s an aftermarket forged crank. I didn’t like the amount the input shaft was sitting in it when I took the box out.

 

[johng]

I know next to nothing about gearboxes, so how would the spigot bearing cause it to jump out of gear?

 

[Oneball]

I know next to nothing about gearboxes, so how would the spigot bearing cause it to jump out of gear?

The input shaft isn’t well supported it’s only really got one ball type bearing so the spigot supports it too. If it wobbles about you’ll get misalignment between the input and the mainshaft at the point where 3/4 synchro is.