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MG MGB Technical - Axle Noise after Thrust Washer Replacement

I finally completed the Thrust Washer renewals on my Tube-type diff. While at it, I also had the axle bearings replaced on both axles. I'm an average mechanic (below average on this board) but everything went together thanks to all the info.

I took the car around the block. All went well - for about 300 feet, when a slow knocking sound started to make itself known. It accelerates on speed and does not sound good.

My guesses are:
1. Axles aren't on tight enough? I used small tools (1/4 inch ratchet) and generally don't overtorque things. I did tighten the big axle nuts to 150lbs, but perhaps not the four ones that hold the casing and brake drum. Could this have loosened again, driving around the block?

2. The peg came out and now the pinion is falling apart? I'm nervous because I re-used the pinion pin and decided not to heed Steve's advice with the cotter pin. (I was concerned it might break inside the diff for some reason)

3. Unlikely - The bearings were put on wrong? Do they have insides/outsides or are they flat?


I know I will probably have to go through everything again. However, I'd appreciate some pointers as to where to look first...

cheers
philip
Philip

If you used a 1/4" ratchet on the axle bearing caps I'm almost sure they aren't tight enough. They should be torqued to around 25-30 lb. ft. I'm not sure if being loose would cause a problem as the manuals don't specify torque for those nuts. I think I would also remove the differential cover and check everything to be sure there isn't something falling out or loose. The thrust washers do not always solve a clunk problem. I have done my car two times and it still has a clunk, probably too much gear lash. It's been the same for several years.

Clifton
Clifton Gordon

The clunk itself was remarkably fixed - at least for 300 feet. As you say, it didn't magically turn it into something new, but it's much better than before.

The noise I hear now is different than the clunk. It's more like a rhythmic knock.

I'm also wondering if my torque wrench is off.
Philip

Hi Philip.

If the 150ftlb nuts are that loose, the wheels will be able to wobble side to side, and you will easily feel it if you grab the top of the wheel and shake it in and out when the car is on the floor.

I would jack the back of the car up solidly, jack the axle to get the wheels etc in the position they are when you are on the road, chock the front wheels, and run it in gear to see if I could locate the noise. If it is rhythmic, and speed related, it must be something that is going round.
It could be a propshaft joint, loose drive flange on the axle, chipped tooth in the differential, or even as you say, the peg has come out, (but I really doubt that).

If there is no noise, try gently applying the handbrake to put some load on the transmission.

A worn propshaft joint shows if you grab the shaft and the drive flange and twist back and forth, you will feel any free play.



Do have someone with you, just in case of the car falling and trapping you.

Martin Layton

I forgot to say, the bearings are not handed, and if you turn a wheel by hand when it is off the floor, the axle DOES sound like a bag of bolts in a cement mixer!
Magically, this noise goes away when you drive it!
Martin Layton

Thanks, Martin. Those are great pointers. I recently replaced both U-joints, so I know the propshaft is solid.
I sure hope it's not the diff teeth, as they were fine when I installed the washers.

One thing I noticed, was that the pinion took a lot more strength to hammer out than it did to replace. That makes sense, of course but there's a lot of talk about ovalization on the boards. Is it false economy not to replace the pinion?

I'll be back under the car next week - with bigger tools.
Philip

The nock can even be associated with not having the lugs tightened enought as I found out once when getting my car back from the body shop. A rythmic knock as you say... So definetly sounds like something not being tight enough could definetly be the culprit. Id say if you have a tourque wrench use it ! If not, buy one its money well spent. I personally should buy one of the "click" types instead of using the older version wrenches. And aparently my spelling is horrible today and I dont feel like fixing it so my apologies...
James

Raise both rear wheels off the ground, put the car in neutral and have a helper turn one wheel while you turn the other at the same speed. You want both rotating forward as they would while driving. If it is in the dif you should be able to hear the knock.
John H

When you reassembled the carrier did you put the shims in the correct way?
M Mallaby

M, you have me wondering.

Which shims? It seemed pretty straight forward. I took off the hub, oil seal collar, bearing hub caps, oil seal, and took out the axles. I took them to a machinist who put on new bearings I'd bought at Moss.

In the diff, I took out the differential gears (Moss#267-095), replaced the fibre washers (267-140) and the copper washers (267-130). The fibre washers didn't seem directional, and the direction of the copper ones was self-evident.

I don't recall encountering this part: #125-640. I would think this spacer is part of the bearing assembly, which I didn't do. Is that what you mean?

Again, thanks for all the info. I'm getting ready for another cross country drive (my 3rd in this B) and I want to get there!
Philip

Phillip-
You haven't told us if your car has wire wheels or disk wheels. If they're disk wheels, make sure that the lug nuts are all tight (sometimes it's the simple things). Also, check to be sure that the driveshaft (propellor shaft) is properly assembled. However, since you presumably followed directions in shimming the differential, perhaps you should take a hard look at the driveshaft (propellor shaft)assembly. The origin of that which you describe might be found there.

In all probability, this assembly is original to the car and its maintenance has often been neglected. First, in order to assist in future reinstallation, mark both of the yoke flanges and the transmission and differential flanges. Remove the nuts, washers, and their bolts from both the transmission and the differential flanges, then remove the driveshaft (propeller shaft) from the car, clean it, and put it on your workbench.

Unscrew the dust cap from its sleeve, and then slide the sleeve off of the driveshaft (propeller shaft). Carefully remove both the steel washer and the cork washer. Next, remove the circlips that secure the bearing races in the universal joints. Should any of them seem to be stuck in their grooves, lightly tap the end of its bearing race inward with a wooden dowel rod in order to relieve the pressure on the circlip. Remove the grease zerks (lubricators) from the universal joints as well as from the driveshaft (propeller shaft). Now, tap the radius of the yoke arm with a light hammer in order to loosen the bearings. They should slide out, but if they are stuck in place, use a light hammer and a flat-nosed punch bearing against the shoulders of the races in order to gently tap them out. Take care not to distort the race or damage the needle roller bearings within it. Once they start to move, turn the yoke over and, in order to avoid losing any of the needle roller bearings, hold the bearing in a vertical position and pull the bearing out from below with your fingers. Place the trunnion onto wooden blocks and tap the top lug of the flange in order to remove its bearing races. Finally, remove both the gaskets and their retainers from the journal spiders.

Clean all of the components so that they can be carefully inspected. The cleaner, the better. The threads of both the dust cap and the sleeve should be made free of all contaminants by using solvent and a soft nylon toothbrush. Check the splines of both the sleeve and the shaft for indentation or signs of excessive wear. The grooves should have a smooth, almost polished appearance. Secure the yoke of the sleeve in a vise and fit the shaft back onto the dry, ungreased sleeve. Twist the shaft in order to check for sideplay in the splines. There should be very little. Next, inspect the bearing races and their journals for wear. Carefully examine the faces of the flanges for signs of cracking, as well as the holes in the yokes and the flanges for any signs of cracking or ovality. If you see any of these problems, then these components must be replaced. Ensure that the bearing races are a light, yet tight driving fit in their yokes. If they are not, they must be replaced with new ones.

Once all of the components are in satisfactory condition, you can reassemble the driveshaft (propeller shaft). In order to keep moisture away from the needle roller bearings, apply a coating of gasket sealer to the gasket retaining shoulders on the journal spiders, and then use a hollow drift in order to refit the retainers, and then fit the gaskets. Smear the walls of the races with chilled grease in order to retain the needle roller bearings in place, insert the needle roller bearings, and then fill the races with grease. Be aware that that as there is not enough clearance for a true hex head, or nut, the bolts on the U-joint at the gearbox end of the prop shaft have very peculiar semi-rounded heads. You have to remove the flange to replace the bolts, but this is not a big job. Moss Motors and others sell the right bolts to do the job. Be aware that the amount of torque necessary for the flange nut at the back of the transmission that secures the driveshaft flange varies with the type of transmission:

Manual without Overdrive: 150 Ft lbs
Manual with D-type Overdrive: 100 to 130 Ft lbs
Manual with LH-type Overdrive: 55 to 60 Ft lbs

Note that for easiest access to the grease fittings of the spider journals, the U-joints should always be installed so that when the axle is hanging at its lowest point, the grease fittings point 180° away from each other to the widest, most open side. This would be pointing upwards towards the front of the car on the front U-joint and pointing downwards towards the rear of the car on the rear U-joint. Some U-joints have the grease fitting in the plane of the four spider shafts - these are inappropriate and should be returned to the vendor. The most common and correct U-joints have the fitting out of this plane, i.e., sticking out toward one side. There are four possible ways to install the in-plane joint, and a total of eight for the out-of-plane one, but only one way is correct. The yoke on the driveshaft is asymmetric, having a forged-in depression at only one point where the "ear" blends into the shaft. This depression is for the nozzle of your grease gun. You must use the out-of-plane type U-joint; the fitting must face toward the shaft center, not toward the flange. This eliminates four of the eight possible positions; and the fitting MUST be located in the depression, which eliminates three more. Now the grease gun will fit. If the U-joints are the in-plane type, you can usually remove the existing fitting (or plug) and install a long type fitting to grease it, but it is no fun. Do not leave the long fitting in place, as it will be broken off in operation! Do not make the mistake of installing Borg Warner’s version of the MGB U-joint that comes complete with new clips. Why? Because it has an extended grease nipple (about ¾” - 1” long) that makes for ease of lubrication, but the grease nipple is so long that at the car’s first encounter with a severe road bump or dip it impacts against the yoke flange and is swiftly snapped off flush at the threads. Now, making sure that the grease zerks (lubricators) are facing away from the yoke flanges, insert the journal spiders into the flange yokes. Using a soft drift in order to protect the races from distorting, fit the bearings onto their journals on the journal spiders and into the yokes. Install a new cork gasket (Original Equipment Part # 7H 3880), the steel washer, and the dust cap over the ungreased splined section of the sleeve, then grease the splines on both the shaft and inside the sleeve. Take care to align the arrows found on both the sleeve and the splined section of the shaft so that the U-joints will be properly operating in plane, then slide them together. Finally, fit the washer into the dust cap and then screw the dust cap tightly onto the sleeve.

All that remains now is to clean away any excess grease and then you can reinstall the driveshaft (propeller shaft) onto the flanges of the transmission and the differential. Do not forget to install the lock washers! It should be noted that whenever a driveshaft (propeller shaft) is installed, the axis of the flange yokes on both the transmission and the differential must be aligned parallel to each other in order to avoid producing unequalized thrust forces that will damage the bearings of the U-joint as well as result in driveline vibration.
Steve S.

Steve,

I have Rostyles. The U-Joints have less than 1000 miles on them. Now, after your thorough (and welcome) description, I'm wondering if the work was done properly.

However, there was no knock before changing my thrust washers. This leads me to believe the propshaft was fine. There was some minor vibration at speed which I attributed to the worn differential.

I have yet to take the car on a good spin. I'll be back under the car next week, and give you the updates.
Philip

Hi Philip,

If you did not remove the carrier to replace the fibre washers then no need to worry about the shims. They are located outboard of the carrier bearings.

Sorry for the alarm.

Mark.
M Mallaby

This thread was discussed between 09/08/2007 and 13/08/2007

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