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TR4/4A Pinion Oil Seal Replacement

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mcmillal

mcmillal

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Well, after putting it off for a long time, I finally got under the car to replace pinion seal. Everything has gone quite well. I had a bit of a surprise when I went to remove the castled nut from the front of the differential and found it was not much more than finger tight. Might explain a few things. So I have two questions. First, does anyone know the torque specs for this nut? Secondly, how much play, if any, should there be on the pinion shaft, fore and aft, at the front of the differential housing? I hope I asked the second question correctly. I'm assuming that if the nut is torqued correctly, if will address the play in the pinion.

Thoughts?

.........Alex
 
The nut helps set the preload in the pinion gears. Normally, if you are just changing the seal, you'll mark the nut and return it to the mark after replacing the seal...pluses a bit extra. Like half a flat. Yours being loose is not a good sign, as it means your pinion has been running loose and therefore out of alignment with the ring gear. That is likely WHY the seal died on you.

There are only two reasons the pinion nut would be loose. One is a PO mis-installed the pinnion and/or forgot to tighten it. The more likely scenario is that one or both bearings are shot. Either way, it's time to get in the manual, check the bearing condition and re-set the pre-load correctly.
 
Just for clarity, there should be _no_ fore/aft movement of the pinion shaft at all. When the book talks about measuring pre-load, they are actually measuring the drag in the bearings caused by having less than zero clearance.

If you torque the nut to spec (85-100 ftlb) and can still feel any fore/aft at all, then it's probably best to pull the axle right now and hope you can reuse some of the parts. But if it pulls up snug, then I'd try running it and see what happens. Pulling the axle isn't a lot of fun; and if you do have a failed bearing then likely the damage is (mostly) already done. You might want to try to measure the pre-load before installing the new seal, but I probably wouldn't even bother with that.
 
As noted by CJD, the usual drill is to mark the nut and count the turns, replacing the nut the same number of turns, to the mark, and a scosh more. Full torque on a reinstall is not good as it reloads a bearing that is already worn, inducing more rapid wear and sometimes very rapid failure. In you position, I would tighten til the slack goes away and add maybe half a flat.
Bob Hustead
 
Was there a cotter key in place? when I visualize the drag/preload on one of those, I think of a front wheel bearing and how I tighten them up until I feel and see that there is drag on the tire because the tire does not turn freely. In this case you want to leave some of the drag in place. The drag left is slight and measured I believe in inch pounds, so it is difficult to feel that slight amount, but you can. There is a tool for it, but I have only seen pictures. You want a slight drag and like suggested read up on it.
Anyways a brief explanation is that you create this drag by adding or subtracting shims. The bearing itself looks just like a front wheel bearing with a race. In your case, I would pull the bearing; it is just sitting right there, and look at the race and check them both for pitting. If you only drive the car around town on weekends, I would be tempted to put the shim pack back in and a good bearing in and set the drag accordingly.
 
Thanks for the replies. There was a cotter pin in the castellated nut, which was a major PITA to get out. The bearing looks to be ok and there doesn't appear to be any major scoring. I did mark the nut before removing it. But when it came off without any effort at all, if figured it didn't matter anymore and I'd torque it to spec when I replaced it.

At this point, I'm going to leave it as is, see if the leak goes away, and drive it about for the fall. If need be, I'll add it to my winter project list. :smile:

I'll let you know how it goes.

Thanks everyone, Alex
 
Woo hoo! Success! Not more leakage from the differential. I filled the differential with oil, started her up, went for a drive, and no leaking. Even after an hour or so. I'm quite pleased. What I'm still not too sure of, is the noise I hear driving in third, and even more so in fourth. I was hoping that fixing the leak and putting in fresh gear oil would have made a difference. I think it did somewhat, but when I'm on the gas in third or fourth, there is quite the noise. Not a grinding noise, more like a loud whining noise. I'm thinking transmission now. Any thoughts?

I do have a spare overdrive transmission I am hoping to have rebuilt and installed this winter.
 
More likely damage to the gear teeth in the differential, from the loose pinion nut, IMO. The gears are very precisely matched as any mismatch will cause them to howl. The rear end in my TR3 does the same thing, even though the gears looked fine before I installed it. Not sure why it's so much louder in 3rd & 4th, but it sure is. And the noise definitely started after switching the axle, the previous one was dead quiet.

In 4th gear, none of the gears in the transmission are carrying a load, the input shaft is just locked to the output shaft. So any possible noises should be the same, power on or power off.

PS I had definitely planned to replace the howling axle long before now (with 3.45 gears and a LSD), but got caught up in other events. The good news is that it doesn't seem to be getting any worse.
 
yeh I wish I was more of an expert in this area, anyway how I see it is the rear axle matches road speed and when you are in 3rd and 4th the road speed is greater. Like Randall suggested the problem is probably the gear meshing especially after you mentioned the pinion was loose. However, I would probably pull the axles out and switch them if I had some axles setting around just see if it is not an axle bearing. I would also make sure the 85 pounds of toque is on the nut and there is just that small amount of drag on the pinion, but then again if I had a complete rear end set up that I thought was good, I would swap that in, but then again have you look at U joints to see if they have sloop because they match road speed also.
 
This is all good. Thanks. I do, in fact, have another set of axles. That would be an easy enough swap. I also have another complete ring and pinion that's in very good shape. The U joints look and feel pretty good. I have a spare driveshaft with U joints and flanges in my boat load of extra bits and pieces too. What I don't have is that special crank case spreader that lets me get at the differential to remove it. I'm thinking I can test one thing at a time to see what makes a difference and what doesn't. So, first off I'll clean up the two spare axles I have and give that a try.

Keep the opinions coming.

Thanks folks.
 
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