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Triumph TR6 - Laws of Nature - Where's the Plug?

My transmission has begun to make a whirring noise over the last couple of years and I think it is because the fluid has leaked out of the rear differential (TR6's are known for this) and I would like to (a) check and (b) refill if necessary. I do not drive it enough that I have caused any damage to it but I would like it filled before I do any more.

The question is how do I check it and refill it. I have looked at catalogs like MOSS and they show a "drain" plug. I have been under the car and see no plug. I am now assuming that the whole drawing I am looking at is flipped 180 degrees and the plug is on the top?

If so how the &^%I^(#%@#%$ do I gain acess to it. If I have missed the plug (I didn't spend a large amount of time looking cause I was woried about the car falling off the jackstands and putting a small indentation in my head) how do you fill the transmission from the bottom up?

Help !!!!
P.S. it as '72 but that shouldn't make a difference

Brent Wilson <- Its slowly falling apart like my Triumph
Brent Wilson

Hi Brent
How r u doin'?
First off let me assume you are wanting to fill the differential and not the transmission. The fill plug is on the pasenger side of the dif about half way up on the front side of the dif (infront of the whole drive assembly to the wheel). I have a small hand pump that will fortunately screw on to a 5 L. jugs. This I attach a plastic hose to ( both available from crappy tire) in insert it in the hole (Don't laugh). Then pump her till oil starts to come out (I hear you laughing!). Also check that at the top back pasenger side there should be a small hole with a cotter pin in it. this is for pressure relief ( the cotter pin to help stop stuff from entering) ...this should be checked to see if cotter pin is there and it is free to move about. I know this from before the body went back onto the frame...I do not know if you can reach it now. Maybe a mirror on a telescopic handle will help.
The transmission fill is on the driver side towards the back and again half way up the body of the tranny ( just back of the bell housing). I use same procedure to fill the tranny
I still visit your web page once in a while.
Best regards

Hey Brent,

Just to let you know that not all the diffs in a TR6 have a plug hole. My 1975 does not have a hole in the cover plate as it is so well illustrated in parts catalogues. It does though have a breather hole on top with a cotter pin attached. I filled it that way. Guess BL had different suppliers or the worker responsible for putting it in was off having a pint or two.

I spoke to other people a couple of years ago in the Toronto Triumph club about this very problem and some have taken the back plate off, drilled a hole where is supposed to be and braised a nut on to the plate and used a short bolt to plug the hole.

Since I don't have access to welding equip I never did this modification but do occasionally check the level with a wooden shish-ka-bob stick. The diff tends to leak where the half shafts are inserted .

While the method that Rick said with the tranny is correct one point must be made...if you have an o/d it takes a while for the oil to flow into that part so usually I will fill it and take it for a short drive (switch the o/d on and then come back and recheck it.

Hope this helps


I found that it is much easier to fill the differential by removing the right rear wheel and reaching over the exhaust and axle. The fill plug is in plain sight. I also have a rubber hose I attach to a plastic bottle as in the earlier response.

Hi Folks,
I'm currently working on restoring a 75 Tr6 (body off - lots of frame welding!!). I was also surprised that my diff. didn't have a fill plug for the oil. All the comments have been real helpful, but how do i assure thatmy diff has the right amount of oil in it. I can drain and refill it with the amount indicated by my manual, but when checking what is the appropriate level. (having a fill plug eliminates all of the above)
Also, how do you actually fill it up through the "breathing hole"? - whats the technique?

Thanks for your help!

Aivars Berzins

This thread was discussed between 22/06/2001 and 24/06/2001

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