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MG TD TF 1500 - Differntial operation

Hi

Happened to have the car (1950 TD) on the lift today and turned one rear wheel gearbox in neutral. Now I would have expected the opposite wheel to turn in the other direction, it did not it turned the same direction. I held one of the wheels and turned the other the held wheel wanted to turn and could not be held. To me this implies that the differential is not working. The car drives with no noise from the rear end. Can anyone throw any light on this, sorry for the difficult explaination as to the problem.

Barry
B Bridgens

Barry, The only reason I would think that would happen is the spider gears are locked up for some reason, either done for racing or a foreign object found it's way in there binding the gears. The only way to know for sure is to split the case. PJ
PJ Jennings

Hi PJ

Thanks for the reply, I purchased the whole rear axle assembly with MGA gearing. When I replaced the axle it didn't occur to me to ensure that it worked as required. You are right I will probably have to take a peek.

Barry

B Bridgens

Hi

Got the car in the air on the lift to remove the rear axle, but looking at it I thought is it possible to remove the side without taking the whole axle out of the car. I need to remove the diff to check it. I will need to remove brake pipes etc. and the drive shaft and support the half that is left attached. Is this something that can be done?

thanks

Barry
B Bridgens

Barry,

It can be done but it will be a lot easier to pull the whole axle, especially whet reassembling. I would try to free the diff before doing any dismantling. To do this you could jack ONE wheel off the ground and, with the car in neutral, try to turn it in both directions, (you could use a breaker bar on one wheel stud). That way you may feel what is amiss. If that doesn't work drop the jacked side and try the same thing on the other. If it does free up you will need to drain the oil to see if any bits have dropped off.


John

J Scragg

Barry,

I should have added some safety instructions for this test: Use axle stands as well as a jack and chock the wheel that is on the ground.

J Scragg

Could be differential is shimmed tight.

If the wheels turned in the same direction, the driveshaft had to be turning in neutral, too.

Jack it up one side only and see if you can spin the wheel and driveshaft in neutral, see how much resistance there is.

You might have someone drive it in circles in a parking lot slowly and observe whether it is rolling free or tires are skidding.

It might only last another 50,000 miles.
JIM N

Hi

Thanks for all the suggestions, I have had enough for today so I will have a go in the morning and see what happens.

Thanks

Barry
B Bridgens

If it is still on the lift, put it in gear and turn a wheel. You'll likely find the other now rolls the opposite direction and you'll know how much effort it requires.
JIM N

Hi

Carried out the tests.

One wheel locked the other turned but very notchy and a little stiff.

Propshaft locked one wheel turned the other goes in the opposite direction once again notchy.

The pinion turns very freely with right amount of backlash.

The notchiness feels like a square ball in the race.

I have receipts from when I bought the diif. for pinion bearing large and small and carrier bearings X 2.

My guess is that one or both of the diff. carrier bearings have malfunctioned due to too much preload.

Do you think I am right? If so I will order the bearing and gasket before I remove the axle from the car.

thanks

Barry
B Bridgens

Barry,

You should also order some carrier shims. I got mine from a person who restores VW beetles, they are used to adjust clearance on the crankshaft.

John


J Scragg

Hi John


Thanks for the reply and reminder,I have some shim steel and some VW/Porsche end float shims. If the bearing are tight I suspect that I will have to take material off unless the builder put too many shims in. The preload is very small 0.002inch for each bearing. I'll order parts tonight.

Barry
B Bridgens

Barry,
I use 56 x 72mm DIN 988 shims for the carrier which are a better fit than the VW crank shims.
0.2mm cost 83 cents each.
https://www.agrolager.de/product_info.php?products_id=40001693
Regards
Declan
Declan Burns

Thanks for the tip Declan, picking up the bits tomorrow so busy days Thursday and Friday.

Barry
B Bridgens

Hi and HELP

OK removed axle and fitted new bearing did all the measurements and reassembled. On the bench I pushed the half shafts in and tried the differential operation, smooth as silk. I put the axle back, put in the half shafts and the brake backing plates tigtened up the wheel bearings and I am back to the same problem differential not working. I have checked the spacer is OK behing the wheel bearing no problem. At the moment I have the halfshafts lightly inserted into the axles with the wheel bearings pushed in about halfway, the differential works fine. I am in desperate need of ideas or a suggestion as to what is wrong.

HELP

Barry
B Bridgens

Hi

Just pulled one of the half shafts and found some witness Mark's on the inner splines (see photo). It seems the splines aren't long enough and are putting load on the bearings. I have measured the shaft and have the following:

Overall length 71.5 cms 28.5 inches
Bearing shoulder to inner 58.4 CMS 23 inches
Useable inner spline length 3.3 CMS 1.3 inches

I have nothing for comparison and cannot find any internet measurements. It would seem the inner splines are too short or the carrier is wrong. I am running wire wheels.

Barry


B Bridgens

First, check the spacer is the correct way round, it has a chamfer that butts up to the shaft shoulder.
Second, measure the half shaft. From the shoulder to the diff end of the shaft should be 23".
Other MOWOG car and vans used similar axles but with longer half shafts, I think the Wolseley 4/44 had a longer shaft that people shortened to fit the T's and Y's. I also think the spline had to be extended. Shoulder to start of splines is 21.125"
Too long and it will bear on the diff gear cross shaft or bind on the splines and preload the diff gears
Ray TF 2884
Ray Lee

Looks like shortened shaft, should be 1.875" spline length.
I posted before I saw your measurements
Ray
Ray Lee

Barry,
I have a set of hardened half shafts from Dave Clark in my garage awaiting installation. The splines section measures 4.5cms which is 1.77".

Regards
Declan
Declan Burns

Hi Ray

Thanks for the reply, I think you are spot on. The inner end of the shaft looks cut with grinding marks on it. The sline length is too short and I have ended up with exactly as you describe. I am not sure how easy it is to extend the splines or wether they are case hardened. I might just have to bite the bullet and buy 2 new shafts £600 ouch.

Barry
B Bridgens

Hi Declan

See my reply above. Thanks for confirming the measurement.

Barry
B Bridgens

Barry,
join the Octagon MG Car Club, shafts are £190 each + delivery. Still a lot of money but better.
I have seen them cut back with a disc grinder, these shafts break easy anyway so I would not risk it.
Ray
Ray Lee

Barry,

There are two critical dimensions on the half shaft which you need to check:

1/ With the bearing and spacer correctly in place measure from the inner face of the bearing to the inner end of the half shaft. should be 23.15"

2/ The usable length of the inner splines (straight section of splines) should be 1.3" minimum.

If you have these dimensions, the shaft is correct. I measured these from my old shaft and used the wear marks to get these values.

John



J Scragg

Barry,

There are two critical dimensions on the half shaft which you need to check:

1/ With the bearing and spacer correctly in place measure from the inner face of the bearing to the inner end of the half shaft. should be 23.15"

2/ The usable length of the inner splines (straight section of splines) should be 1.25" minimum.

If you have these dimensions, the shaft is correct. I measured these from my old shaft and used the wear marks to get these values.

John



J Scragg

Barry,
Here are some measurements I made on the Dave Clark half shaft.

Regards
Declan

Declan Burns

The critical measurement is from the shaft shoulder to the start of the spline. The witness marks clearly show yours are wrong.
The shaft would have Slocum centre drilling if it was not butchered. It is binding on the diff gear. The length of the spline is not critical but where it sits in the diff gear is.

Ray
Ray Lee

Hi Ray

It was butchered and will be consigned to the scrap bucket, looking at new axles.

Barry
B Bridgens

I whole heartedly agree that we want as much spline engagement as possible but how do you explain an axle that was running previously and now is blamed for binding up the rear end?

If it were me, I'd coat the axle end in Prussion blue, layout dye or some other coating to determine how far it inserts before throwing one away and buying new axles.


You inserted the axles and it spun free; tighten them down and it is bound up. Doesn't sound like the axles are to blame.

I've never had to deal with an MGA rear end, so I took a peek at the Moss Motors catalog for reference. You made sure the shims were installed correctly. The shim for the disk wheels. You have wire wheels, right?
JIM N

I have just been informed by my supervisor/instructor from 60 years ago that it is a Slocombe drill not slocum. At 95 he is still sharper than me!.
Jim,
The only thing that can load up the shaft is the length to the spline start. The witness marks show how far into the diff gear it goes. The gear is binding where the spline machining starts to rise.
Ray
Ray Lee

Hi Ray

You apprentices are all the same you never listen.(LOL)

On your advice I have joined the Octagon Car Club so I can take advantage of the extremely competitive prices. The marks on the splines show how much pressure was being put on the splines metal was raised. There were no holes at the end of the shaft only grinding/cutting evidence. The length of the usable spline was at the bare minimum if not below hence the distortion of the metal when the the wheel bearing housing was tightened. Anyway for peace of mind and to get the right parts, new shafts, wheel bearings,oil seals etc.

thanks

Barry
B Bridgens

Hi Jim

Thanks for your comments, see my reply to Ray. I purchased the rear axle as a complete unit and fitted without opening up. The car came with a MGA rear axle with all its associated problems. I never checked the operation of the differential, it was only by chance when I had the car in the air that I noticed it was a problem. When I took the axle out of the car and drained the oil there was evidence of severe wear in the oil. When I took out the diff bearing they were badly worn, the rest of the axle looked fine with no discernable wear on the gears. The axle was reassembled with new parts as above and the problem was evident.
For peace of mind and to get the right parts in the axle I am buying correct half shafts I hope this will cure the problem which certainly point to incorrect bodged parts. I will let you know.

Barry
B Bridgens

Does that mean you'll reinstall the spacer meant for disk wheels only?

Don't feel bad, you discovered your problem in the garage. Our TD has MGB rear end and front disc brakes, and a front wheel bearing went out stranding us this evening.
JIM N

Now I am confused, there is a spacer between the bearing and the shaft shoulder for both disc and wire wheels. See figs H15 and H22 in the WSM.
Ray
Ray Lee

Hi Ray

I don't which spacer Jim is referring to. The configuration of the axles are the same for wire or solid wheels. The diff spacers or collars are needed to set the diff preload and backlash, the other spacer is behind the wheel bearing which is the same part number for both axle configurations and for the TF.

Barry
B Bridgens

Moss catalog shows "Item 46 SPACER, disc wheels" but none for wire wheels. Try fitting the axles without the spacers and reevaluate.
JIM N

Hi Jim

I only see item 46 as the drain plug on the Moss site.

Barry
B Bridgens

MGA rear axle isn't it? Or a TD with MGA gearing?
I looked under MGA
https://mossmotors.com/rear-axle-1

JIM N

Hi Jim

It's a TD axle with a MGA C & P, sorry if I was'nt clear in my description.

Barry
B Bridgens

Hi

New half shafts arrived from MG car club today big difference, just need to fit them this afternoon.

Barry

B Bridgens

Welcome to the Octagon MG Car Club. I have been a member since 1976 and like this BBS the members are very helpful when in trouble.The spares are quality and reasonable price.
Ray
Ray Lee

Hi Ray

Thanks, I ordered other parts together with the half shaft excellent prices. I was very impressed with the quality of the shafts and their packing was exemplary, carrier cost was super low. They are now fitted and hopefully out for a run tomorrow. Thanks again for the recommendation.

Barry
B Bridgens

This thread was discussed between 23/03/2019 and 18/04/2019

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