Yet another hidden problem with my new MK IX

I’m trying to determine how deeply I need to go in order to find all the problems with this car, but this one was a surprise. I was shifting cars around in my driveway and suddenly the MK IX wouldn’t move either forward or reverse. However, the speedometer indicated that the car was moving, even in neutral. I crawled under the car and saw that the U-joint and its driveshaft at the rear of the transmission was spinning but the rear driveshaft wasn’t. Using tow straps and my floor winch I was able to maneuver the car into the repair bay and get it into the air. There I discovered that the rear flange on the front driveshaft was not turning when the front driveshaft was turning. I disconnected the rear driveshaft from the flange and discovered that the big nut that attaches the flange to the front driveshaft was loose. It had a split pin in it but I could turn it back and forth with my fingers as far as the pin would let me. I removed the front driveshaft flange and this is what I found:

…and this is what the inside of the mating flange looks like:

It appears that there should be two keys in there locating the flange to the shaft with the big nut attaching the flange to the shaft with a sticky taper. Instead of keys I see that someone has apparently drilled a hole through the flange and the shaft and put a bolt through it, which has now sheared off. The remains of the bolt can be seen in the first picture.

This doesn’t appear to be salvageable to me. Does anyone by chance have a spare front driveshaft from an automatic transmission Big Mark?

If no one pipes up with what you need give Welsh Jaguar or Jaguar Heaven a try, as they part out old Jaguars and sell recycled parts.

Jack White aka Jagnut Spares (Luray, VA) has a yard full of Jag saloons, including a few Mk IXs, if I recall. He will probably have what you need.

I figured out why that bolt they put through the driveshaft sheared off. The engine can theoretically put out 240 ft-lbs of torque. That then goes through the torque converter and gets multiplied by two. Then it passes through the gears for a further multiplication of 2.3, producing 1100 ft-lbs of torque at the driveshaft. The radius of the drive shaft cone where the bolt hole was drilled is 0.5", or 1/24 of a foot, so the force in lbs on the 5/16" diameter bolt was around 26,000 lbs. in shear. Even if you count both ends of the bolt it only has a cross-section of 0.15 square inches of metal to withstand that force. It seems to me that putting any kind of bolt there is not a suitable repair technique, and I now have a higher respect for what a drive shaft has to withstand.

What is the length of that? I have some here but maybe from a Mk7 w/o auto. Is this the section with the center bearing stuff?

I am not 100% certain exactly what area or part is defective, but believe you are describing the front half of the driveshaft from a DG250, and the defective area is where it connects to the centre bearing ?

Similar to what Art may have, I have a complete drive line from a 4 speed MK7

I presume you want the front shaft ?

I do have the relevant Parts Manuals to x-ref part nums if you would like ?

Its not expensive to have a driveshaft shortened, not sure on lengthening
We are fortunate to have a driveshaft specialist nearby

This is an automatic transmission car and according to the parts manual this driveshaft is different from a car with a 4-speed. My problem is with the front driveshaft, the one with the bearing on it. That driveshaft splits in two in order to insert the bearing and then goes back together to become one piece. Someone didn’t put this one back together very well and it spun at the joint. Then they tried to hide the problem by putting a bolt through it. As you can see in the pictures, the Morse taper is totally destroyed and the keyways are no more.

I don’t know what the difference is between the A/T and the 4-speed shaft, but this front shaft measures 27 1/4" flange-to-flange. I speculate that the DG-250 A/T itself is longer than the 4-speed, which would require this shaft to be shorter. Is anyone in a position to measure the length of their front driveshaft?

Is the Mk IX driveshaft the same as the Mk2? I have a '62 Mk2 auto trans 2-piece driveshaft and a '66 Mk2 manual trans 1-piece driveshaft in my basement. I could measure it for you

It looks like the short end is 17 1/4 and the long end is about 37 3/4", flange to flange.

Would it be any trouble to get the manual transmission driveshaft length? I have one that’s supposed to be for a manual car, but I’m not sure. During my restoration ony mk2 I’m converting it to manual. Thank you!

Hi Tim, my MK2 with overdrive uses a single piece driveshaft which is about 37" installed, which doesn’t take into consideration the sliding joint. It would be a little shorter than that fully collapsed. If yours is in that ballpark it’s probably correct. A driveshaft for a 4-speed would be a little longer.

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Thank you Mike,
My car will be 4 speed overdrive, so that should be a good measurement.

I have 2 MK7 driveshafts, a 4 speed and MOD.

I will measure today

I also have a MK10 driveshaft. I believe it had a BW8 auto trans

Will measure, as I have to take some pics today, including the clock parts I sent a PM to you about

If someone happens to have a DG tranny with bellhousing and JL (for example) stand them up on the BH and measure the dif in height.

The MK7 Manual calls out all the front propshafts as different part numbers for each manual GB

fwiw, the one I tried to measure was ~ 18" flange end to flange end

the MK10 is a different setup, fixed front shaft is ~33", rear shaft has the splines

As I mentioned, its really handy for me having a guy ten minutes away that is a driveshaft specialist, took over the shop from his old man, now he is an old man

He would probably make you one from scratch cheaper than getting one shipped

The 2-piece drive shaft I have is about 54" from flange to flange, total length.
The 1-piece drive shaft I have is about 44" from flange to the end of the splined end. The yoke end is not attached and I may not have it.

Assuming the 1-piece goes with the car I have, it has a 4 speed manual with overdrive. The 2-piece was in the trunk of a junked '62 with an automatic, so I assumed it went to that car.

I’m seeing 18 and 26 Both of these are center support type. I have more carefully measured the longer one standing on it’s flange with a yard stick. It is 27 1/4.

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Well, my buddy Tom Brady from New England came through with a complete A/T driveshaft from his extensive collection of spare parts. I replaced all the U-joints just to be certain that I would have no more trouble in that department, because I want this car to be a reliable driver that I can comfortably take on tours. Now I just need to convince the transmission to start in Low gear and stay in Intermediate for a suitable time.

As you would know, most people dont have very good things to say about the DG250, especially including its ability to keep oil inside

It may be good or bad that your car was in a museum for the transmission seals

I could not even give away 2 x DG250 trans to members of my club with MIX and had to actually give them to the scrap metal guy

Knowing what I do now, I would have taken them apart, as this serves 2 functions

  • preservers rare spare parts (which can be eBay if you dont need them)

  • I did this with a BW8 in preparation for having to rebuild mine. I learned so much
    that I didnt have to take my trans out to fix it, and I later used a NLA part out of the
    stripped one to do a further repair

Some parts of these trans are NLA, so its good to have a spare if you have space

I recently installed a used auto trans in my 4wd that I had bought for $200

The price quoted by the trans shop was 5k for a rebuild plus $1500 to R&R

Yeah, I’ve thrown two of them away myself, thinking that I would never need them.