For everything you have riding on this, I would still open it up to see exactly what you have, no more guessing. Wouldn't hurt to change the fluid anyway.

 

Wmachine, Kurt,

I did have the fluid changed a few days ago. I do know it is not a posi rear. Do u think I should open it up and measure the gears?

Tell me is there an easy way to convert it to a posi? I have found someone selling a true 1970 W-27 rear end. Would that be worthwhile?

 

If the 3.23:1 gearing with Anti-spin was an option would there be another code or listing on the window sticker beside the G80 code that indicated the 3:23:1 optional gears?

 

SuperCars unlimited sells a unit that will slip into your current rear and make it a limited slip. I believe it's called a locker? Check with them on the price but I am thinking around 4-500.00 for the unit and then you need to install it or have it installed.
The W-27 is pretty rare and prices reflect that. If you are going for originality and you want everything to match your window sticker, the W-27 will be an expensive option that probably will add value maybe, or to some numbers matching finatics it could be a wash in the overall price of the car.
Assuming your car is the one in the picture and you already have invested quite a bit of money, I would try to find the correct rear end if the current one is found to be not the original.
If you like the looks of the w-27 and get bored, buy it and put the original one away to go with the car if you ever sell. You could always put the original back in to sell it as all numbers matching. Depending on what you pay for the w-27 you could always sell it down the road and it will more than likely hold it's value.

 

Yes, I would go back in, but you don't need to count, the ring gear will have the ratio and date codes stamped on it. That's all you need.
I'd also take a pic of the carrier and post it. Then we'll know what you have, and what you may need.


That's what makes this difficult. The G80 Anti-Spin option is an extra charge option so it shows up on your window sticker. Whether you have the TM 3.42 or the SF 3.23 is a no-cost selection, so it does not show up on the window sticker.
Yes, if you don't have an Anti-Spin carrier, one can be added and still use your housing and gears. Jim at JD Race (http://www.jdrace.com) can probably set you up with a factory unit.
Re the W27 rear you found, I'd guess the price is about $5k, and since the W27 isn't original to your car (yes, *that* would be on your window sticker), *I* wouldn't go with it. Certainly not with 3.91 gears with your auto and AC.

 

Kurt,

Thanks again.....ur advice make sense.

OK, I finally got hold of the options sheet for the 442. My sticker as u know lists the G80 which is Anti-spn, but is also lists C60. C60 required the 3.23 axle ratio. So.....I think that resolves it. My car should have a 3.23:1 "posi" with (as mentioned previously) the SF stampted on the tube.

 

Well the good news is that I have now found 3 available axles. One in the UK of all places. Another true aluminium housing w-27 about an hour from me and another non-27 SF in FL.

Though the W-27 is not original to the car I am wondering if even given it is 1.5x the price is it is worth getting and putting in.

Any thoughts or advice is much appreciated.

 

thanks this helped me out a lot! im going to switch from 3.42 to a 3.08 rear gear now!

 

Hardluck, are u going to sell your 3.42?

 

1.5 the price of a non w27 - sounds like a great price to me - if you don't get it please PM me the details, thanks.

 

Good thread.
If you want to try and calibrate your tach you need a portable tach (tach and dwell meter works well for this).
Pull the dash trim and remove the tach from the dash. You can now get to the tach wire on the back of the tach. Alos you will see a round silver sticker near the top in the center of the back. Carefully pull this up to expose an adjustment screw. Now you can start the car after connecting the external tach. You can ground to the ground straps in the dash. Compare the two tachs and adjust as needed.
When I did mine I checked idle, 1500 and 2000 rpm for acuracy. Worked like a charm.

Good luck with the axle hunt and I hope this helps with the tach.

Randy

 

Wish I had known that 20+ years ago. Being curious as to why I could start out in 4th gear and why I was turning a million RPM at 6o mph, I pulled the cover off and counted teeth. 29 on the ring and 9 on the pinion. Divide the two and you get 4:33. Before that I chalked the tire and driveshaft and counted tire revolutions to driveshaft turns. That put me in the ball park.

 

Just on a chance, do you still have that diff. I know it was 11 years ago, bit my 68 post came with the T3 and power 4 piston calipers. A spare diff would be nice.