Robert Garrison

Hello,
I have a 67 427-400 convertible with 4:11 rear en gears that I would like to swap for 3:55 gears for better highway performance. Here’s my question- is there a template or kit to cut a section from the floor above the diff to enable removal of the diff bolts without having to remove the cross member?
any advise is appreciated.
Thanks.
RTG

Dan Hampton

Normally, it is a matter of drilling holes and not cutting out a section. It is pretty easy to "eyeball" where the holes need to be drilled.

GTR1999

Of course, it's your option but cutting the floorboard to remove the diff is an old deal. IMO it is better to remove the diff with the crossmember and keep the floor intact, especially with a nice car like you have.
If you have a 411 GM, then you will need to get a 3 series posi with the 355's. Don't expect to see a huge gain in mpg, the RPM will still be over 3k.

Vet65te

Robert - Welcome to the Corvette Forum. When you can, post up some pics of your 67 L68. I didn't think you could order 4:11's on an L68 (or L36) originally, were they added afterwards?
I'm with Gary, avoid, if you can, cutting the floor on your 67. What trans is in your L68? If it's a wide ratio box, maybe consider dropping down to 3:36's or maybe even 3:08's.
We have a long running thread going on 1966 L72's and even though they were originally equipped with close ratio Muncies, some of them were ordered with 3:36's for
better highway mileage. Don't hold me to this but I seem to recall at least one that was running a 3:08 diff setup.
Mike T - Prescott AZ

C2Racer

As Mike said, I have a 3:36 in my L72 right now and the car can still spin the rear tires at any moment. And I have a 3:08 on the shelf for any long excursions. Best of luck.

Steve

PWPOOP

Well, Here is how "Bubba" did it on my 67.... I agree with everyone else. Don't do it. PO also broke a u joint apparently. I included a pic if you want to swap your shifter easily too




Darin

Vet65te

Darin - Your pics brought back memories, and not good ones, of the floor pan in my 65 Coupe way back in 1985, thanks to the previous owners lead foot.

Check out the bottom pic and notice the gaping hole caused by a 'blowed up' U-Joint. We discovered '3' holes when we pulled out the carpet.
But obviously, when you see the pics, the floor pan holes were not our only focus.
Mike T - Prescott AZ

OldVetteguy84

I am confused. Cutting the floor would make getting at the u joints easier. But why would you cut up a nice car for that?
But you can just unbolt them, then unbolt the case halves and drop the front half out.
I blew up a few rears drag racing, and while it was a messy job, not that hard.

I used to do it in the driveway. To this day I hate the smell of 90 wt!

PWPOOP

Is nobody going to comment on the short shorts? My kids & Gkids give me a bunch of crap when they see my old pic's. I just tell them Back in the day we had sexy legs & liked to show them off

Darin

C2car

[QUOTE=Robert Garrison;1607065288]Hello,
I have a 67 427-400 convertible with 4:11 rear en gears that I would like to swap for 3:55 gears for better highway performance. Here’s my question- is there a template or kit to cut a section from the floor above the diff to enable removal of the diff bolts without having to remove the cross member?
any advise is appreciated.
Thanks.
RTG[/QUOTE ] this is the best way to do it

Bob Rosenblatt

Robert
the speedometer reading on you dash will not be accurate if you switch to a 3:55 rear. It would require removing the transmission and replacement of the aluminum gear. The gear on your transmission is designed for 3:70, or 4:11 the gear is different for 3:08, 3:36 and 3:55. Someone might make an adapter but I am not aware of one.