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TR2/3/3A Rear differential

carpecursusII

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I have a TR3A that as of today has 40 miles on the restoration. Things are going pretty well considering the background. I purchased the car as a half done restoration, the PO had done all the frame and running gear. I exchanged the original gear box for a Tr6+A-type OD. Now my problem......

I seem to have a fairly loud whine from the differential when the car is coasting and I let off the gas. I know the PO was in there and did something because gasket were replaced and everything looked very clean. It is full of oil and makes no noise under load.
 

TR3driver

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I'd double-check the axle end float and that the nut on the input is tight; just because those are a lot easier than what you'll probably have to do. If that doesn't help, you'll probably have to either live with it, or overhaul the rear end.
 
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carpecursusII

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OK, how do I check the end float. what is the torque for the input nut, that is relatively easy to check/adjust. I have no problem living with it as my intention is to sell this car asap and buy the next project, I just want to make sure I'm not setting the next owner up for failure.
 

Geo Hahn

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With the road wheel off and both rear wheels off the ground you push & pull on the hub while having a dial indicator in place against it to measure the float. The specs are in the manual. Float is adjusted by the addition or removal of shims behind the hub.

Can't comment on the torque on the pinion nut (I think that is what is being referred to) as I always mark it and count the turns so I can put it back where it was. There may be a torque in the manual.
 

TR3driver

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The factory TR3 manual doesn't have it, for some odd reason. But the TR4 manual (which is the same axle as later TR3, just wider) gives 85-100 ftlb.
 

titanic

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The factory TR3 manual doesn't have it, for some odd reason. But the TR4 manual (which is the same axle as later TR3, just wider) gives 85-100 ftlb.
If you mean the "big red book", mine has the pinion torque listed in at least 3 places. It is in the torque specs in the general data at the beginning of the book, on page 2 of the rear axle section, and also in the data box page 3 of the rear axle section.
Berry
 

TR3driver

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If you mean the "big red book", mine has the pinion torque listed in at least 3 places. It is in the torque specs in the general data at the beginning of the book, on page 2 of the rear axle section, and also in the data box page 3 of the rear axle section.
D'oh !

BrainFart.gif~original
 

TR3driver

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Nope, just confusion on my part. I looked up something a few days ago that wasn't in the TR3 manual, but apparently that wasn't it.

As my late wife used to say, "I'm gonna like it in the home ..."
 

titanic

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Yes, we should be the life of the nursing home, spending our final days performing imaginary tasks on our invisible cars while on our way to the big TR factory in the sky.
Berry
 
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carpecursusII

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Just to close this thread out, I fixed the axle float and got it down to .004-.005. I removed the drive shaft to find that the pinion nut was finger tight and did not have a cotter pin installed. I torqued it to 120 and bolted everything back up, final result, shes just as quiet as can be. Thanks again to you guys
 

sp53

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Just in case you did not know that bolt is a tricky one. You want all that torque, but you also want just the right drag on the bearing. The shims let you tighten the bolt to the 120 and let the bearing move without heating up. I saw a tool once used for setting it and it kinda looked like one of those old school fish weighing thingies. That is why most people put everything back just the way it came out when they replace the seal. Anyways I mentioned it because the other guy rebuilt it.
 

TR3driver

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Hopefully the guy who rebuilt it got the shims right; because you can't measure the preload with the seal installed.

Not sure why you over-torqued it, seems like a risky thing to do to me, when bearings are involved. The extra load on the bearings can lead to early failure. 20 ftlb probably won't make much difference, but why take the risk?

Also, in general, when the book quotes a range of torques, it means that is the accuracy allowance for your torque wrench. Given the usual uncertainty (no torque wrench is perfect even if it was just calibrated yesterday), best practice is to aim for the center of the range, not the top.
 

sp53

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Yeh right Randall a 100 is enough. Here is the shade tree hillbilly way that I have replaced the bearing and race and seal when I know they are toast. Get the car up nice and high and I impact gun the nut lose then remove the seal. Check and count the shims. Get the new race in and grease the bearing just so it is not dry. Get the castle nut to move nice and easy with my fingers and then start adding shims until I feel about 10 to 12 to 15 pounds of drag. I say feel because I do not have the proper tool. You will have to check the proper number. Then I torque the bolt down and feel it again to see if it tightened up too much. If so, I add a shim. The whole feel deal is kinda Luke Skywalker mechanics, but what the heck I am a Jeti Night. Then take it apart and put the seal in with the desired amount of shims. I try and torque it to 100 and if the cotter key hole does not line up, I use the impact gun to drive it in and yes that could easily get to 120. I have done it this way on cars I have driven for 30 years.
 

CJD

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The way I learned to change a pinion seal is to mark the nut before removal, and then retorque to the mark plus a 16th turn. That wouldn't help in this case, as the nut was loose to start with!
 

TR3driver

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Get the new race in and grease the bearing just so it is not dry. Get the castle nut to move nice and easy with my fingers and then start adding shims until I feel about 10 to 12 to 15 pounds of drag. I say feel because I do not have the proper tool.
Well, I guess there is no arguing with success. But the factory pre-load figure is only 15-18 INCH pounds of torque, meaning 1.5 ftlb or less. Even at only 10 ftlb, you're going to be wasting an awful lot of power (and heat!) in those bearings. I actually have a tiny 1/4" drive torque wrench that will read that low, but it shouldn't be too hard to find something that will apply the right amount of torque just from it's weight. Haven't measured, but I suspect a 1/2" ratchet handle would be about right. Or use a T-handle and a fish scale, as someone else suggested.

Took me a lot of years to notice a correlation between using an impact gun and bearing failure. But that's something else I don't do any more. This is from a diff that someone else supposedly rebuilt:

 

titanic

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The pinion bearing pre-load spec given in the manual is measured with the carrier and seal removed. Otherwise, the drag of the carrier bearings, pinion meshing with the ring gear, and seal will give a false reading.
Berry
 
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