Spitfire Spitfire rear hubs - where to position bearing?

[guzzul]

I am rebuilding my Spitfire rear axles and am in the process of assembling the rear trunnion and positioning it on the axle shaft. I'm not sure how far along the shaft to drive the main bearing (and therefore position the trunnion).

Both the Haynes and Leyland manuals only talk about where to position the 'flinger' at the back of the trunnion. They say to position the front of the flinger at 5-3/4" from the threaded end of the axle. On my axles the flingers will drift all over the place between 5-3/4" and 6-1/8" from the end of the axle. If I push them back to where the axle shaft swells out, its around 6-1/8" from the threaded end. Maybe they're just too loose?

So where does the trunion go? Should I position the start of the flinger-recess (at the back of the trunnion) at 5-3/4" and just forget about where the flinger is? It would be helpful if the manuals indicated where the face of the main bearing should be from the end of the axle, rather than where the flinger is. The face of the main bearing is flush with the front of the trunnion.

I have (hopefully) attached a picture. Right now, I have positioned the main bearing race (and therefore the front of the trunnion) 2-1/8" from the NON-threaded start of the axle, with the thinking that the wheel-mounting flange that goes in front of the trunnion is actually 2-1/16" in depth, and the flange will not go onto the shaft any further than 2-1/16". I'm not sure if this is correct, but it makes sense to me. When I looked at the old wear patterns of where the bearings and seals were before, it would seem to be correct. At this position, the start of the flinger recess at the back of the trunnion is indeed about 5-3/4" from the threaded end of the axle, give or take.

Has anybody been through this before? Am I on the right track here? Before I drive the wheel flange on I want to make sure...that flange is a bear to get off!!

 

[billspit]

Well I've done it on my Mk I and I am drawing complete blank. I don't recall having any questions when I did it, which would have done according to a Haynes, Bentley and a Clymer (the Clymer can be totally wrong at times) manual.

I'm think that putting the on the hub along with the backing plate and tightening to the specified torque will locate the bearing correctly. If I recall I will try to check my manual tonight and get back.

If you didn't use a proper puller to remove the hubs from the axles, there is a good chance you may have bent them. I should know.

 

[guzzul]

I have been noodling along with this a bit more too, and here's my latest brainwave.

The grease flinger is sloppy as heck and seems to not be a very good reference to use. I don't know why the manual wouldn't just give you the reference point from the end of the axle to the front of the trunnion. Too easy I suppose.

If I use the back edge of the trunnion as a reference point (not including the rear seal, which sticks out from the back of the trunnion and actually sits inside the flinger), then maybe what the manuals are getting at is to initially position the back trunnion edge at 5-3/4" from the threaded end of the axle.

I measured both the trunnion and hub/flange. The trunnion body is 2-3/4" deep, the hub is 2-1/16. The threaded portion of the axle is 1". Add them all together, you get 5-13/16". Maybe the idea is to mount the trunnion 5-3/4" initially, and then, as you suggest, when you torque the hub down the whole thing will move together.

Right now, when I mount the hub just finger-tight, it stands proud of the unthreaded part of the axle by about 1/8". This leaves a gap of 1/16" between the back edge of the hub and the front bearing race of the trunnion. If the hub torques down 1/16", the back edge of the hub would sit flush against the race of the main bearing. But the hub would not be totally flush with the end of the axle, it would still be 1/16" proud. Maybe thats where its supposed to be(?).

If the hub torques down 1/8", then the trunnion is 1/16" too near, and the whole shebang would have to move along the axle an additional 1/16", ending with the hub pressed up tight against the bearing race at the front of the trunnion. The back edge of the trunnion would be 5-13/16" from the threaded end of the axle.

I was assuming the hub torqued down flush with the front edge of the axle - maybe it doesn't? 1/8" seems a long way for that hub to move. Even finger-tight it's pretty snug.

I just don't want to jamb these hubs on and find I'm wrong. As you note, getting them off is tough. I know they are relatively easy to bend. I took them in to a Jaguar dealer and they had a proper hub-puller to get the hubs off initially.

Thanks for checking Bill.

Ross

 

[billspit]

OKAY. I checked an Autopress manual that I've used in the past and been pretty happy with it. The grease flinger is driven onto the axle the distance indicated just to give it some clearance for the trunnion. If it is a loose fit, you may need to get new ones. When I did my car, I could not find them, but I think they are now available.

Otherwise, it is just a re-assembly as I said and i think you know. Drift the inner bearing into the trunnion the specified amount or it may actually bottom out and follow with the seal, being careful it is the correct direction. Then put the outer bearing in until it bottoms out on the trunnion. There may be a seal outside the outer bearing. Carefully insert the axle into the trunnion and push all the way through. Follow with the two plates and backing plate on the trunnion. Place the hub onto the axle followed by the washer and retaining nut. Tightening to 110 ft lbs (better double check that) of torque should locate everything in the correct place. If the grease flinger is not over the end of the trunnion tap it back down until it is. The flinger is really there to keep water and dirt out of the inner bearing but it doesn't need to waller around on the shaft.

Its not as hard to remove a hub from an axle that has recently rebuilt as it is from one that is 25 years old with rust etc inside of it. I removed my hubs while on the car a second time and it was a piece of cake. But I had a real hub puller.

Write back if you have any questions. And if anybody knows I've given bad advice chime in.

 

[guzzul]

I think I understand how it is supposed to fit together now. Based on what you say and also on my own fiddling, I think I need to pull the trunnion down towards the end of the axle a little more before I mount the backplate and hub.

The manual is a little goofy giving such a precise instruction for the flinger, and then virtually no instruction as to where to position the trunnion. Particularly when the flinger is basically a 'cap' for the trunnion, and will just get pushed along the axle anyway as you torque it all down. But there, that's just a whine. I feel better now....

I'm thinking I will reposition the trunnion and main bearing face about 2-7/8" from the threaded end of the axle (1-7/8" from the finished end). The backplates and seal plates mount on the front of the trunnion, but don't actually sit on the axle and don't affect this measurement at all. The hub will go on next, and will sit flat against the bearing race. If torquing it down to spec moves it all 1/16", it will move the back of the trunnion to 5-3/4" from the threaded end. If it torques a little further, so be it. It's not going to be more than an additional 1/16".

Thanks for helping me think this through Bill. I wasn't sure whether the hub was actually in contact with the outer bearing race, but obviously it is. I'm pretty confident now on what I should do.

Will let you know how it goes.....cheers.

Ross

 

[billspit]

I think you are correct.

 

[guzzul]

Hey Bill - just to let you know, I drifted the bearings on as noted above, stuck the hub on and torqued it to 110 ft/lb. Wound up with the back end of the trunnion right on 5-3/4", right where it should be. Both axles are now installed.

Thanks again.

Ross