c3 drive shaft length

[Kenny C.]

Hello
I am just finishing the drive train on my 69 SB M21 restoration but am having some trouble with the main drive shaft. I purchased a replacement shaft with universal joints because the original was very severely rusted. When I went to install the shaft yesterday it seems that it is too long? I checked it against he original and it is the same. The shaft can be installed if I pull the caps off and wrangle it into the rear end yoke and then put the bearing cups on. My concern is that with this so close on the length will the present any issues with bind or bumping into the tail stock? And since this seems to be the same as the original that I took out so long ago that I cant remember what the install was like could there be another issue going on here? The motor and Trans mount dropped right in easy as can be and seems to line up perfectly.
Thanks in advance for any help.

[Edward J.]

Re: c3 drive shaft length

Ken. You'll Need Some Clearance, The Slip Shaft Needs To Move Alittle When You Hit Bumps In The Road, Check The Brackets That Mount The Engine To Craddle To See If There Alittle Room Maybe To Slide Forward , I Beleive There Is, And Check The Cross Member For The Trans For Slots To Move. Where Any Of The Mounts On Engine Or Transmisson Replaced? Possiablycausing A Clearance Problem.

[Terry M.]

Re: c3 drive shaft length

The usual change of length of the prop shaft is not needed on C2 or C3 Corvette because the engine and differential are in fixed positions. Other than the small amount of play caused by the rubber mounts for each power train part there is no change in length -- so the usual inch or two change in drive shaft length that happens because of the suspension travel of a rear-wheel-drive vehicle with a live axle just isn't there on a 1968 + Corvette.

Have you ever seen the underneath of a C5 or C6? There is a drive shaft tube that would take a bulldozer to move -- well a major accident will do it, but short of that there is no flex there at all. That alone was wonders for chassis regidity -- but that gets us into another subject.

[Edward J.]

Re: c3 drive shaft length

Terry,im Not Thinking, The Axle And Trans. Are Fixed, But I Know My 72 Has A Slip Yoke In My Auto.thm400 And Ive Had The Axle Out A Few Times Theres No Clearance Issues Putting The Shaft Back In, In The Case Of Not Being Able To Install Shaft Correctly, Ken Must Have Something Not Algin. With The Drive Line, Which I Would Suspect Something Has Moved Slightly.ie Mounting Of Trans.or Engine.

[Michael B.]

Re: c3 drive shaft length

Kenny,

Look at the internal splines of the slip yoke. Sometimes they can be worn enough or even twisted to prevent the yoke for sliding all the way onto the transmission output shaft. Look at the line on the yoke where seal sat. It's usually a little rusty on the outer section. You should be able to push the yoke a little further into the transmission.

The slip yoke should be about 1/2 to 1-inch from the full in position when the driveshft is installed and secured. You should be able to install the slip yoke and move it all the way forward into the transmission. Install the drive line and align the rear u-joint and secure it first. Then, with the transmission in neutral align the yoke and front u-joint and slide the slip yoke back and secure.

[Terry M.]

Re: c3 drive shaft length

Ed is right -- there is a slip yoke at the back of the transmission -- both the manual and shiftless transmissions. I'm sorry if I created the impression that there was no slip yoke in my earlier post. However, on Corvettes of the 1968 and newer variety that slip yoke doesn't normally travel through any distance once the prop shaft is installed. There should be enough movement in it to easily install the prop shaft. Perhaps those who have suggested wear or corrosion are on to something.

[Kenny C.]

Re: c3 drive shaft length

I have a new trans yoke so I cant tell from a rub mark how far it used to be into the tail stock but it does go all the way in until it about touches the rear seal so I dont think there would be any way to get any more out of it. Now that it has been pointed out to me that the differential and trans are fixed and the relationship does not ever change I dont suppose it makes much difference how tight the space is as long as the shaft will go in. It just seemed odd to me that the GM engineers would make it so close wheen they did not need to. And everything else in the drive line fits perfectly so I dont think there has been any movement and the frame mounts are not worn or sloted so I feel that the engine and rear end are where they are suppose to be. It's in and I presume it will be fine so unless someone thinks there really is an issue that would damage something Im running with it.

[Dennis D.]

Re: c3 drive shaft length

Is that new yoke the same as the old one? This was a long time problem. What was sold as the correct trans yoke for your car, would not work. Were enough problems that a company in Calif (I believe) reproduced it.

What you used to get....



the right one....


Big difference in the boss height

[Kenny C.]

Re: c3 drive shaft length

BINGO!!!!!!!!!!
Thats it my yoke is exactly what you have pictured here and now makes perfect sense. The added lengeth at the saddle piont is just enough to make assambly a problem. Now for the fun part trying to get Eckler to take it back.

Thank you all for your help, nice to know there are folks out there with such vast knowledge available.

Best Regards
Kenny

[Dennis D.]

Re: c3 drive shaft length

BINGO!!!!!!!!!!
Thats it my yoke is exactly what you have pictured here and now makes perfect sense. The added lengeth at the saddle piont is just enough to make assambly a problem. Now for the fun part trying to get Eckler to take it back.

Thank you all for your help, nice to know there are folks out there with such vast knowledge available.

Best Regards
Kenny

Don't ask how I knew this. Also there might be some NOS ones out there for big bucks, due to the rarity. Not anymore. Should find them under 100.00. The company repop'n offered me one for 65.00 for helping with the ID a few years ago. Think most venders sell them and are aware of the difference. If Ecklers didn't know...... shouldn't be your problem. Checked Ecklers site they have the piece........

1963-70 (C2, C3) Driveshaft Slip Yoke For Cars With Manual Transmission
Corvette Driveshaft Slip Yoke, For Cars With Manual Transmission, 1963-1970

• Reproduction Of Original
• Fits 1963 With Muncie Transmission
• Fits 1964 With 3 Or 4-Speed
• Fits 1965-67 All With Manual Transmission
• Fits 1968-70 All Except Automatic Transmission
• 27 Spline
• Replaces GM # 3868728

Item# 35388 In Stock
$99.99 ea.