TR3A Rear Axle rebuild

[PhilExe]

Firstly happy new to you all and may 2017 be filled with TR action.

The pinion flange on the differential of my TR3A axle (Girling Type) recently fell off, the castellated nut came undone, looks like it probably never had a split pin fitted. The pinion shaft has a lot of play in it both side to side and longitudinally which allowed the pinion gear to rub against the carrier. It's not looking to bad as I stopped moving pretty quickly.

I am sure the pinion bearings have excessive wear and the pinion gear will probably need to be replaced to.

Does anyone have any experience in rebuilding of a rear axle? It seem that splitting the casing is a specialist job. Am I better off to just try and locate a reconditioned axle.

Thanks

Phil B

[Motorsport Mickey]

You can mackle up a diff casing spreader if you find it necessary but most people mange with large pry bars or screwdrivers, it's only a matter of a few thou spreading to remove and refit the diff.

Unless you're eager to delve into the diff without consideration of condition I'd be temped to retighten the pinion nut (to the correct torque) and start to make some considered measurements of cross axle end floats and pinion shaft movement etc (use a DTI, clock). Good information of tolerances and methods to adjust from workshop manuals or websites. Most of the various items on TRs are extremely agricultural and you can get away with abuse and ignoring symptoms which would prove fatal on many more sophisticated machines. Not recommending abuse or non servicing but why not take advantage of it's inbuilt strengths which is why it's lasted half a century in the first place ? You might still be within it's tolerances and can be back on the road within the blink of an eye.

I'm never sure of the attraction of machines which need to be watched like a "baby in a high chair" (they can't be left alone either, you always have to be at them), I'd rather be driving them.

Previously I'd have always dropped my axle off with ex works axle guru Ken Tomlinson but he passed away a couple of years ago, I'm sure Pete Cox will do you a great job if you go as far as wanting a rebuild.

 

Mick Richards

Edited January 1, 2017 by Motorsport Mickey

[BlueTR3A-5EKT]

You can mackle up a diff casing spreader if you find it necessary but most people mange with large pry bars or screwdrivers, it's only a matter of a few thou spreading to remove and refit the diff.

Unless you're eager to delve into the diff without consideration of condition I'd be temped to retighten the pinion nut (to the correct torque) and start to make some considered measurements of cross axle end floats and pinion shaft movement etc (use a DTI, clock). Good information of tolerances and methods to adjust from workshop manuals or websites. Most of the various items on TRs are extremely agricultural and you can get away with abuse and ignoring symptoms which would prove fatal on many more sophisticated machines. Not recommending abuse or non servicing but why not take advantage of it's inbuilt strengths which is why it's lasted half a century in the first place ? You might still be within it's tolerances and can be back on the road within the blink of an eye.

I'm never sure of the attraction of machines which need to be watched like a "baby in a high chair" (they can't be left alone either, you always have to be at them), I'd rather be driving them.

Previously I'd have always dropped my axle off with ex works axle guru Ken Tomlinson but he passed away a couple of years ago, I'm sure Pete Cox will do you a great job if you go as far as wanting a rebuild.

 

Mick Richards

+1

 

The only issue may be road rash on the pinion flange seal area. - Dress clean with a file and stone to remove burrs that would shred the seal as you refitted it. If so bad consider either a replacement flange or a repair with 'SpeediSleeve'

 

Then - new seal, retorque flange, fill with oil and off you go.

 

The small (front) pinion bearing can not fall out if the flange is removed unless you have lost the seal too.

 

The pinion can migrate toward the crownwheel carrier if the pinion flange is removed. but the bevel of the gears tends to push it toward the front of the axle as it all turns in a forward going direction (hence the bigger pinion bearing to take the thrust load when driving)

 

Cheers

Peter W

[56TR3driver]

FWIW, here's a photo of the "big pry bar" method. Done on an IRS (Stag) diff, but works exactly the same on a TR3 (I just forgot to take more photos).

 

But I agree with the above about putting it back together and seeing what's what. It's possible that running with the nut loose has damaged the bearings and/or gear teeth, since the pinion would be trying to run at an angle, but there is a reasonably good chance it's OK.

 

Note that the pinion & ring gears are a matched set and should be replaced as such. New bearings are often slightly different than the originals, so you'll also need to check preload and mesh.

[arthur r]

I've rebuilt my differential twice. Once in the '70s and recently last year. It was also rebuilt by a well know TR specialist in the 90's but was very noisy (whining on the overrun) which is why I had to rebuild again. I found it easy to remove the diff from the casing without a spreader just using tyre levers. Both times I rebuilt I took great care to get the dimension form the top of the pinion to the centre line of the crown wheel exactly correct measured to 1/10th of a thou! I also blued the teeth after setting the preloads to ensure the pressure point was in the middle. The first time in the 70s I was a foreman in a tool room so had access to metrology equipment to do the measurements. As I am now retired this wasn't an option so I use parallel bars on the top of the diff casing and measured with slip gauges. IN both cases when I rebuilt the diff it was nice and quiet. I also used new bearing s on both occassions but bought genuine replacments SKF/ NTN last time. they cost nearly £500 for the set but I least I know where they were manufactured. I know of rebuilds using cheaper kits from "god knows where" but they destroyed the diff after a few miles.

[Ian Vincent]

I rebuilt my diff using a couple of tyre levers - no problem. I also used a set of engineers parallels and a depth mic to set the pinion depth - again no problem.

 

Rgds Ian

[Chris Hubball]

Hi Phil

 

Take it to Pete Cox , he has just rebuilt my TR 4 rear axle first rate job does not rip you off.

 

Cheers Chris