Topic: 68 Driveline Discussion - Big Block Auto and 4 speed Discussion

[Bob Gaines]

I thought that extreme difference would illustrated the differences to the reader. As you so wisely pointed out, there are many factors as to why each has its own application.  The difference between the driveshafts may not be significant, but it does exist.

"The difference between the driveshafts may not be significant, but it does exist." is not in dispute. My question that I have been trying to get answered is , what was the apparently not so signifigant difference that justified the different clasifacation?

[67gta289]

How about some 1968 MPC data.  Hope this helps

The most interesting to me is for 68 the 302 except GT being 50-31/32" long, but the 302 GT being shorter at 50-7/32".  Would the higher GT spring rate be the reason for this?  The only thing I can think of.

[TLea]

How about some 1968 MPC data.  Hope this helps

The most interesting to me is for 68 the 302 except GT being 50-31/32" long, but the 302 GT being shorter at 50-7/32".  Would the higher GT spring rate be the reason for this?  The only thing I can think of.

Good thought but the reason there’s a difference between the GT and the non-GT is the GT have a 9 inch rear end and the non GTA has an 8 inch rear thus the need for different lengths
 Back to the 428 or big block  ones. There is a difference in length between automatic and four speed. There is a difference and slip yoke‘s. Any other differences I am not aware of

[67gta289]

Thanks Tim, that slipped my mind

[67gtasanjose]

The 68 MPC clarifies a lot for the 67/8 cars when you consider the transmission's overall lengths (C6 being much longer than 3 or 4 speeds and C4) and whether or not a 9-inch is in the car or 8-inch. The cardboard liner and/or tube-type seems to make up the other variations.

[ruppstang]

What was the cardboard lined style?

[67gtasanjose]

What was the cardboard lined style?

Most solid tube shafts were, it looks like the tube-in-tube were not lined. Look again at the columns in the MPC and you can see which "type"s did use the liners. I see liners being used very often still today on other vehicles.

[J_Speegle]

Going to split the thread and make the later posts - 68 Driveline Discussion - to keep things neat and tidy

[rodster]

All very interesting information.  Never knew about cardboard lined driveshafts.

I also find it interesting that lengths are measured down to the 64th.   Could that be an example of engineering vs practice?