TECHNICAL TIPS - SON OF DR. BALLJOINT

by Steve Henrys - Sprint Magazine, July 1982 (typed for use on TVRCC-WWW by Don Davis, , with a couple of my own comments added)

The story so far: Our handsome devil-may-care hero, after having his TVR sprayed a really nifty shade of black to the joy and admiration of all passers-by, has decided that its performance in the ride and handling department is on the awful side of not very good. With a view to improving it he has acquired some spare parts and has already replaced the front suspens ion. Now read on...

The rear suspension of the Vixen is, well, different. It is independent with coil springs and double wishbones holding a cast alloy hub carrier. The differential is the Vitesse unit, 3.89 to 1 and the drive shafts are from the Triumph 2000/2500 saloons, except that the outer end has an identical fiting to the inner, instead of a stub axle. The part #s for the u-joints are QL16103 (Quinton Hazell).

The wishbones are of TVR manufacture, the lower one incorporates a control arm for toe-in adjustment and the upper has a facility for adjusting camber by way of shims. The hub carrier is also a TVR special. It is an alloy casting, with all the electro-chemical problems that that entails when it comes in contact with steel. In other words, don't try to remove any bolts from the hub carrier, such as the hand brake cable bracket, they break off. I know.

The brakes are the TR6 variety-Girling 9" x 1.75" drums with leading and trailing shoes. (By the way, the rear brake hose is the same as the front.) The stub axle or quill shaft, which runs through the hub carrier and bolts to the drive shaft, runs in two identical bearings, part # 1988-1922 (Timken) and of course there are oil seals at each end but these aren't the same. Between the bearings is a short squash tube. This is supposed to take up the playbetween the bearings, as they wear slightly the bearings are tightened and the squash tube deforms a bit further, but more on that later.

Through the bottom of the hub carrier passes the pivot rod, to which is attached the lower wishbone and the coil spring/damper unit. This is secured by two cotter pins which work the opposite way round to the system us ex-Healey/MG owners are used to. Whereas on the rustbucket the fulcrum pin has the cutout into which slides the cotter, on the TVR it is the cotter which has the cutout. If, in ignorance, you try to hammer out the cotter, you stand a good chance of destroying everything. Instead the cotter must just be loosened and then the pivot rod may be pressed out. I'm afraid it really is a job for a press, there is no other way to get it out, and it isn't the only part of the job which requires a press.

Let me say here and now that there is no way that one can replace Vixen rear wheel bearings with the hub on the car. The reason is that the outer bearing cups need to have great force applied to get them out, and similarly, the new ones need to be pressed in. In fact, I hammered mine out, but having done that I would not recommend it to anyone else. It took a long time, required a great deal of effort and was potentially very damaging to the hub carrier.

After jacking the car up and supporting it properly, take off the rear wheel. The brake drum is removed by undoing the two securing screws and prising off with a suitable lever. (Don't forget to release the hand brake and back off the brake adjustment). The brake shoes are removed, trying as always not to pinch fingers. Remove the retaining clips and lever the shoes out of their slots. Don't lose the pieces of the brake adjuster mechanism. Undo the four bolts which attach the drive shaft to the hub. As the brake shoes are off, it is relatively easy to remove the handbrake cable. Push the outer cable towards the center of the car out of its retaining bracket and then pull the inner cable out of the slot. This allows the end of the cable to be brought clear of the hub so that the clevis pin may be tapped out after the retaining clip has been prised off. Disconnect the brake hoses.

It is easier to unbolt the wishbones at the chassis and remove the wishbones and hub carrier together than to try to take the hub carrier off the wishbones in situ.

Having got the assembly off and cleaned away as much of the crud as possible it is time to begin renovating. You should, of course have a set of replacement parts on hand, i.e., inside and outside seals, new 1988-1922 Timken bearings and new squash tubes.

Firstly, remove the split pin from the castellated nut that was covered by the drive shaft. (The easily visible outer nut is a blind, there to get you to do something stupid.) Remove the castellated nut and pull or tap out the splined flange which bolts to the drive shaft. The quill shaft ought then to come out the other side with a few taps of a soft hammer. It will have on it the inner race of the outside bearing and the squash tube. The inner race of the inside bearing and the inside oil seal will still be in the hub carrier, but these are tapped out easily enough.

Removing the outside bearing inner race from the quill shaft is more difficult. Trying to lever it off is a complete waste of effort, so being a bit stumped I called Doug Manuel who gave me what I suppose are the only two real alternatives, neither of which sound very pleasant.

The first is to take off the rollers leaving only the inner cone, then take your best cold chisel and sharpen it. Support the quill shaft on something solid, place the cold chisel on the bearing and give it a sharp whack with a large hammer. "The bearing race is quite brittle and it is possible to break them" Doug told me. The second is again to take the rollers off the inner race and grind through it. Obviously you need to be careful to not grind the shaft, but once a split has been made it is easy to tap the bearing race off.

(As the person typing this I would like to suggest a third and easier method. Remove the rollers as with the other methods and then heat the race with an oxy-acetylene torch. Just make a cherry red spot on one side and it should fall right off. I don't feel the heat will damage the quill shaft, but I hated Materials Science class, so what do I know? )

So, at this point you should have a bare quill shaft and a hub with two old bearing pieces in it. Find someone with a press and get them pressed out and the new parts pressed in/on. I went to a local engineering firm who did it for me straight away.

Assembly, as they say in all the worst manuals, is the reverse of disassembly. The only problem was the fact that the squash tubes wouldn't squash! Quite a common problem, I gather. I used all manner of leverage (and brute force) to try to get the damn things deforming, but no luck, it just wouldn't go. I confess, I....er...put the old ones back. Yes, I know.

I was unsure about how tight to do up these wheel bearing thingies. Hand tight plus half a turn locked them up completely. In the end, I settled for tightening them until noticeable play was just eliminated. Is that right? Anyway, I have checked them a couple of times since and there doesn't seem to be any play and the wheel still rotates so I hope that's OK.

(Typist's comment again: I have been told that the rear bearings and squash tube are the same as TR6. If this is true, I would guess that the tightening procedure should be the same, right? The TR6 manual I have says: "Mount a dial test indicator on the hub flange so that indicator stylus contacts the bearing housing. With a rocking motion to settle the components, pull the bearing housing away from the indicator. When the housing is as far down as possible set the dial test indicator to zero. Push the housing up towards the indicator, again with a rocking motion. Note the maximum reading. Tighten the adjusting one flat at a time and check the end float as described. When the end float lies between .004 & .002 inch (.10 and .05 mm) secure the assembly and tighten the locknut. If the end float has been reduced to less than .002 inch (.05 mm), then the collapsible spacer must be renewed. Merely slackening the adjusting nut to give correct end float is a dangerous practice.")

Having three of the mounting points with worn bushes, I obviously had to replace them. I used a small puller to get them out. To push the new bushes in I used a small vice and short box spanner. Because the bush is longer than the mounting it sits in, it is important that the overhang at each end is the same. If it isn't then the wishbone will not fit into its pair of brackets.

Having got the wishbones on, things got easier. Before reconnecting the handbrake cable, I bolted the driveshaft to the hub and then joined up the brake hose to the union. The last major bit to go back is the coil spring/damper unit, which is straight-forward enough really.

It is a good idea to lubricate the brake adjuster, it is amazing how they get crudded up with road dirt and brake dust. My father's foot was pressed into service to bleed the brakes, (I have never before seen brakes where the bleedscrew is below the hose connection!) then they were adjusted.

I don't mind admitting that I was pretty relieved when it was over. Spending a week squatting at all manner of inconvenient angles in a garage is not my idea of a good time. Still it was very worthwhile!
 
 

Rear Uprights: dissassembled rear upright minus pivot bar and companion flange rear upright: assembled, view 1 rear upright: assembled, view 2


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