View Full Version : Help with prop shaft alignment & rear seal

09-07-2006, 12:16 PM
Well, I pulled my prop shaft out last night, as I should have, marked the front & rear at flanges for re-alignment with a heavy permanent marker.

Well, got it up on the workbench & find the marker wasn't so permanent! My **** greasy hands rubbed it off.. I usually punch alignment points, but nooo, not this time.

OK, I didn't replace the u-joints, so the alignment of the front & rear joint are still fine, but now; how or do I really need to match up at tranny & rear? Bently says to. I can't see why at tranny as the output shaft is the same all the way around. Believe so is the same at input shaft on rear.

Any help/suggestions would be appreciated!

Lastly, I need to replace the seal on the front of my rear, do you need to pull the input flange off with a puller to get at it? This I found out after I checked the hypoid level & after filling up found it leaking the next morning. Looks like only way to do seal is drop the rear according to Bentley.

I don't have a lift, so I am laying on my back & I know the weight of the rear!

Guess if I have too I can drill a drain plug & replace the bushings while I have it out. Has anyone done the drain plug? If so how about some tips.

And all this started with installing seat belt mounting points!!

09-07-2006, 12:29 PM
I have never done this on my TR, but for previous Triumphs I have owned the alignment does not matter - so long as the holes in the flanges line up.

I know you can get the prop shaft itself balanced (needs a special machine - just like balancing your tires), but other than that, I didn't think there was much else you had to do. I could be wrong though....


09-07-2006, 12:46 PM
As long as you didn't disassemble the propshaft, you can just bolt it back on. The alignment issue refers to the yokes for the u-joint relative to the (prop)driveshaft. Make sure that the slider is forward when you reinstall, use new locking nuts ONLY(do not reuse), and lube the slide so it's smooth while it's out.

As far as the rear seal, on my solid axle the input flange is just held on by a big nut and secured with a cotter pin. Usually torqued at 80-100lbs (see Bentley) and can be a pain to remove without a lift. To remove, first use a punch and mark the location on the nut and also on the shaft next to it and count the number of threads that are exposed. This is important because you want to put it back exactly in the same position. I'm not sure if your car uses shims or a crush washer (see your Bentley). If the latter, you'll need a new crush washer to set the proper torque on reinstall, well maybe you will - others please chime in on this as I have shims on my pinion and no experience with a crush washer.
Have someone push the brake pedal while you back off the nut to prevent the car from rolling.

To remove the seal, you'll need to drill a hole all the way through the seal (NO FURTHER) and use a slide hammer to pull it out. There have been several posts on this, including one from me so try a search for more info. It is probably a pain to do on your back but I have a lift (bragging) and was relatively easy to do.

Haven't drilled for a drain plug but if you've just changed the rear end fluid, you're good until dead so I would skip the drain plug and avoid further problems.

Hope this helps.

09-07-2006, 01:00 PM
I have a Spitfire, not TR, but I think it would be the same situation. I have pulled the drive shaft, and I wondered about this too. It would seem to me that the only issue would be overall prop shaft balance, not exactly where the flanges align. As long as the flanges bolt properly to the diff/txmission, I don't see how it makes a big difference.

If you have not changed out u-joints, you should not have impacted the shaft balance. Easiest way to know is bolt it back in and drive.

As for the differential seal, again I think the TR would be essentially the same as the Spit. You should be able to change out the front seal without removing the diff. The front hub should come out without a puller. These hubs have fluted shafts, so they are not pressed on the way rear hubs are. they are a little stiff to pull off, but should come ok without a puller.

You need to be very carefull (depending on your diff model) when you take the front hub off. If your diff has a collapsable spacer to set pinion lash, you need to count the turns on the front shaft nut when you remove it, in order to put it back exactly the same way. Other than that, the front seal should be replaceable in situ.

You need to get a tube inside the diff and suck out the oil with a pump or an oil-sucker (Napa sells them, pretty cheap). Getting the tube into the diff is a little tricky because the ring gear blocks access at the oil-hole. But I have managed to snake in a piece of tubing, and suck out most of the gear oil. as long as the diff is drained below the level of the front seal you should not have a lot of gear oil pouring out the front when you pull the hub.

As far as putting a drain plug in, I would not attempt this with the differential in the vehicle. It is not a big job on the bench, but in the car it would be a bear, unless you have it up on a hoist and can work underneath with lots of clearance.

09-07-2006, 01:24 PM
Rob and Peter are correct. The concern is not with the position of the flanges on the transmission and the differential, but with the alighment of the U-Joints on the drive shaft with respect to each other. Out of Phase U-Joints can cause bad vibrations.
This link has some good information about driveshafts, U_Joints, CV Joints, angles and Phasing of U-Joints.
It's been awhile since I took a driveshaft apart. But I think there is a master key in the splines that will allow only one alignment. It's usually a large male key that must be aligned with an equal size female slot in order for the splines to mate. If I'm mistaken about the master key on the Truimph drive shaft. See the illustration on the link for the correct position of the U-Joints.

09-07-2006, 02:54 PM
If you disassemble the two halves of the driveshaft, there are two embossed arrows that must line up (point the arows to each other on each half) to mate the halves properly. The yoke that bolts to the tail of the tranny and input shaft of the diff has a nearly invisible indentation to denote where the grease zerk goes when installing new u-joints.

BTW as far as u-joints, I find it much easier to take the whole assembly to the driveshaft shop. Mine only charges $10/u-joint to remove&place them properly and guarantees their work. Much less frustration and they can balance too for $75 or so.

09-07-2006, 05:14 PM
Thanks all, I thought as much that I didn't need to worry about the orientation at the tranny & rear, but if you read the Bentley it sure sounds that way.

I'll have to rear the manual a little closer about a crush washer, or pre-load that is involved with removing the oil seal. I am hoping it isn't an issue.

This confirms the fact about when you know a British car is out of oil, it stops leaking!

Ah the wonderful smell of fresh 90 weight!!

Again, anyone whose done the diff drain plug please chime in. I'm kinda thinking about drilling a hole & putting a threaded inside & outside plug in with epoxy & having a plug thread into that. If you get my drift.

09-07-2006, 07:23 PM
Gary, I hope that you're up and running for the CCBCC Valley of Sin run on Saturday....

09-07-2006, 07:46 PM

wasn't even on my schedule, my son starts soccer season this sat, so my weekends are pretty full.