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No drain plug on TR4A rear axle


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The rear axle on my TR4A has to my surprise no drain plug. On all drawings in the catalogue there is a drain plug shown. I guess I have to remove the rear cover assembly to get the old oil out. Is this current practice on the US TR4A?

Wilfried

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The rear axle on my TR4A has to my surprise no drain plug. On all drawings in the catalogue there is a drain plug shown. I guess I have to remove the rear cover assembly to get the old oil out. Is this current practice on the US TR4A?

Wilfried

Yes Wilfried, the TR4 sensibly had a drain plug but they used a different diff. casing on the 4A with no drain plug, for some strange reason. I had to put in a new oil seal a few months ago so put new oil in the unit when it was off the bench, along with new bushes all round. If just draining the oil it would have been a pain!

Cheers.

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Just about the start of "sealed for life" units in general manufacturing, they thought all you'd do is top it up.

 

Mick Richards

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It is quite common to add a drain plug when the diff is removed for seals or whatever. There is a round boss on the bottom of the diff just made for the plug location. The plug is 3/8' tapered pipe, same as the one used on the engine&trans. A magnetic plug would be my choice.

Maybe Triumph thought the diff would leak anyway, so a few cents could be saved by eliminating the plug.

Berry

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Drilled hole in the appropiate place

and locked it with a sender for oil temperature.

As I had the oil temp gauge for my engine oil of the V8 already

I added a switch and it was a lot of fun to see the oil temp of the diff.

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Thanks for all your replies and suggestions!

I will remove the rear cover, so I can also check if the play on both sides of the "thrust button" are equal. (I had to shim 0.1mm on the right side, and did not check then).

Wilfried

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Drilled hole in the appropiate place

and locked it with a sender for oil temperature.

As I had the oil temp gauge for my engine oil of the V8 already

I added a switch and it was a lot of fun to see the oil temp of the diff.

What was the highest temperature you measured on the diff oil? My guess would be that it is only a few degrees above ambient, unless you use the brakes intensively?

Wilfried

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The diff dislikes high speed on the highway.

If you let the temp stabilize what needs some minutes constant speed

I would expect about 30 degrees above speed in KM/h

As 170 degrees was the limit on the gauge I can only guess

but it was far beyond 200 degrees.

 

So when we go to Italy down the highway the temp is all the time

around the limit of the gauge unless we go topdown on warm weather.

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Wilfried, which catalogues are you talking about? There isn't one shown in my Stanpart catalogue.

 

Pete

I was referring to the catalogue in rimmerbros.co.uk . They call it the "solid Girling type" and the plug is Nr. 71.

Wilfried

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The diff dislikes high speed on the highway.

If you let the temp stabilize what needs some minutes constant speed

I would expect about 30 degrees above speed in KM/h

As 170 degrees was the limit on the gauge I can only guess

but it was far beyond 200 degrees.

 

So when we go to Italy down the highway the temp is all the time

around the limit of the gauge unless we go topdown on warm weather.

This information is most interesting! On my last journey, the diff was becoming quite noisy. I was afraid that oil was missing. But this was not the case. I read the workshop manual regarding the rear axle and learned that:

Both axles are pushed into the diff. In the center there is a "thrust button". The axial play of the axles should be about 0.1mm, adjustable with shims.

The button should be laterally free, i.e. have the same play left and right. As I had to remove the rear cover assembly, I could see the button..and the missing play at the right side of the button. I added 0.5mm play at the right side: the diff is now running normally quiet!

 

Which brought me to the following consideration: when running the car, the heat is mostly produced at the diff. The diff and the two axles get hot, and the heat is the dissipated by the axle hosing. Therefore the axles are hotter than the housing. They expand more than the housing. With a difference of 16 deg F between axles and housing, the play of 0.1mm is already eliminated!

At high speed the temp. difference could very well be much higher than 16 deg. This means that the rollerbearings will come under high stress. And if there is no play on one side of the button, the diff will suffer also.

 

With the play of 0.5mm this will not happen. I wonder, why the factory advised such little play. What is the disadvantage of 0.5mm?

Wilfried

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Just noticed it is not an IRS?

Thought TR4A is always IRS except some rare US examples?

All my data referring temp are for the IRS, the TR4 stay much cooler

due to the axle tubes on both sides!

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Just noticed it is not an IRS?

Thought TR4A is always IRS except some rare US examples?

All my data referring temp are for the IRS, the TR4 stay much cooler

due to the axle tubes on both sides!

Not that rare for US cars, quite a few have come back over here now (including mine.)

Stuart.

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My car came from the USA. The papers, the batch on the rear all say it is TR4A.

Its chassis number is STC 65 CT 35370, which means it is a TR4.

The chassis is the TR4 type, not th belly type. It is not IRS. It has no sidelamps.

 

My conclusion: it is a normal TR4 which has been sold in the USA as TR4A.

Wilfried

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