Driveshaft weak link

[jensenracing77]

Somewhere in the past I have read that the Jetfire driveshafts would break easy. Is this something anyone knows about? What is the weak link on them? Is there am upgrade that should be done?

[62 Cutlass Convert]

The weak link is the center cardon joint-an early CV joint arrangement with 2 u-joints and a spring loaded centering ball and socket. If that centering ball and socket are worn/broken you cannot get the vibration out of the driveshaft.

The quick check is that if the joint snaps over center it’s “good” for now. If it just flops around it’s not functioning for one of several reasons with that centering ball/socket joint. One of the problems is the ball in the joint is not replaceable, The rebuild kits that are NLA new had a new yoke with the ball that all got replaced. Who know’s how long an old good one will last. Lots of them are being run right now, some of which are no good. Test yours and if it’s bad try to find a good DS or less likely a rebuild kit.

I had a new shaft made locally with modern parts as I needed to shorten it anyway for my trans update. Very stout, modern parts, not cheap. There is also a company in TX that rebuilds the orig DS with a new machined in ball and socket using parts that are available-about $1000 as I recall.

There is a whole discussion in the forum on this but I can’t find it without the old search feature-maybe someone else can.

[jensenracing77]

Thanks, I do remember that thread but I thought someone had said before that it would actually break or snap in half. Maybe I misunderstood what I read, it was several years ago. I have two sets of the slip shaft with the ball and socket and even the spring NOS. If this is the only problem, I am covered. My driveshaft is pitted really deep so I am going to piece another one together out of better parts. I have a nice front section from a 4 speed car and a nice rear section from an automatic car and then the NOS parts. I was just concerned that if a shaft could brake on me I would just take it to a shop and get the ends welded to a new shaft.

[62 Cutlass Convert]

Make sure the u-joint’s are phased properly. I know that’s necessary but couldn’t explain.

Someone here maybe or a driveshaft shop can explain.

It needs to be balanced anyway at a shop.
They can tell you if the shafts still good too.

Replace your center bearing. The one you can buy new is too loose so it needs to be shimmed tight in the bracket.

Guess they can break, seem to remember someone taking about that. Corrsioon would certainly be a problem but fatigue is a well.

[Jim Noel]

I have not heard of a drive shaft breaking apart. I have heard of the vibration problem from the shaft when the constant velocity (CV) joint goes bad. I have also experienced this myself! Attached the GM service guild article.
When the drive shaft is out of the car and on the floor, a good CV joint will not allow the shaft to lay straight, it will want to bend at the CV joint. There are 6 different repair kits for the CV joint!
There are several different drive shafts in length, plus with and without a two piece rear section joined with a rubber sleeve. When making a drive shaft from different transmission cars (auto, 3-speed or 4-speed) be sure the overall length remains the same. There are at least two different lengths for the rear section and three different lengths for the front section.
The center bearing is the same for both styles of bearing hangers, cross member or floor pan mounted.

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[jensenracing77]

I just pulled a driveshaft from a 62 Cutlass for comparison. Ken and Jim were correct about the Cutlass having a smaller driveshaft. The back section between the 63 4 speed Jetfire and 62 automatic Jetfire driveshafts are the same. The front section between the Cutlass automatic and the Jetfire automatic are the same. The Cutlass back section is much smaller diameter. An automatic front section is the same as the 4 speed other than it is shorter so the auto front section could easily be cut down for a 4 speed.

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[jensenracing77]

Had my 4 peed car on the lift taking things apart and noticed that the drive shaft in this car is not the same as any of the others. The front section is the same as my other 4 speed front section. This back section is the smaller diameter but this one was not made with the rubber damper layer like the small diameter Cutlass one. This drive shaft is heavily pitted so with it not having rubber in this one I am thinking about just getting the ends cut off and have a new tube welded in. Not sure yet what I will do for the drive shaft but wanted to post that this is a 4th version. .

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[Jim Noel]

Is it possible that the rear section (or even the complete length) of this drive shaft was replaced at some time? The parts book only shows one drive shaft for all 1962-63 4 speed Jetfires. Maybe the assembly line ran out of the Jetfire drive shafts that day and put in a Cutlass one to move the car down the line? The mysteries of production!

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[jensenracing77]

The two that I have that are cutlass both have the rubber layer but this one does not. Did all f-85 and Cutlass have the rubber? Till now I thought everything in 62 had it. I would assume this to be the original but I can’t say that for sure. Only had 44,000 miles but I guess it could have had one brake maybe and got replaced. I would suspect they had a running change and maybe this was just the early 4 speed setup. I may just change it for the other larger Jetfire shaft I have. Not sure what way i will go on this yet.

[joe_padavano]

Eric, the driveshaft in my 62 wagon does not have the rubber.

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