TR6 TR6 Diff. Drain Plug Question

[bunzil]

I plan on drilling and tapping my TR6 diff for a magnetic drain plug. Six-Pack recommends a standard 1/2 inch SAE magnetic plug, yet others suggest a smaller 1/8 NPT plug. Obviously smaller is easier. Any recommendations here? Also, is there an issue of length with the plug impacting the inner workings of the diff? Most are about 1 inch long, so I wouldn't think so. Thanks.

 

[Andrew Mace]

As most later Triumphs did not have drain plugs at all, I have to wonder just how valuable a magnetic drain plug really is. Easiest all around might be to use the same plug as used for gearbox filler and engine sump drain.

 

[guzzul]

Magnetic seems overkill to me. In a transmission, yes, since you may have the odd bit of stuff you want to collect in the sump and stay there. Differentials should not be losing pieces of metal - if they do, you are in big trouble.

I put a 3/8 NPT plug in my Spitfire. No problem with length of the plug, since there is an existing 'boss' on the bottom of the diff where Triumph used to install drain plugs (earlier models had them). Also with NPT, since it is a tapered hole and plug, the length of 'engagement' is just over 1/4" (I think it's .18" or thereabouts), after which the plug is tight, so not much of it actually reaches up into the diff.

1/8 NPT might be a little small. I thought for 90-weight I would like something that flowed a little faster and went with 3/8 NPT.

It is not a big job if you have the dif out on the bench and already have the case opened, which I did. I would not have bothered unless I had the diff out of the vehicle. You normally don't need to change the gear oil too often in the differential. Seems like not a good return on your time to remove the diff just for this, and I would not try to do it while the diff is installed.

 

[myspitfire]

I installed a brass diff drain plug the same thread as all the other plugs on my car(oil,tranny,diff filler plug))on my late Spitfire.The trick with this operation is to first tap carefully using lots of cutting oil(to trap the fillings)After you bore the hole remove the top filler plug drain the old oil,plug the bottom hole fill with a quart of 'MOTOR FLUSH'(Advanced Auto Parts)with the top plug open introduce a high pressure shot of compress air,at the same time you remove the bottom plug,this cleans & flushes the contaminates & residual fillings.,Then fill with clean oil,plug everything up,& off you go.This is what we did & never had a problem since.Oh!The early model TR's had a 'BOSS'area at the bottom of the diff where the factory placed a drain plug,but on the late models the 'BOSS'area was left BLANK this is the area to drill your hole.

 

[bunzil]

Thanks. A magnetic plug may be overkill, but at around $3.00 why not? Also, can you confirm, just in case, the "boss" area is that little u-shaped area almost dead center on the bottom of the diff, just ahead of the bell housing? Is this correct. I need to replace the driveshaft seal so with the diff out I thought I'd add a drain.

Thanks again.

 

[guzzul]

Yes, thats the area to put the hole. Use a file or grinder to just touch it up and make sure its nice and flat. Then use a centre-punch to exactly locate where you want to drill.

If you are going to try and do this while its in the car, you will want to get a suction-gun and try to get all the gear oil out beforehand (you won't get it all by the way) so it doesn't pour out all over you and your drill when you punch through. Make sure you do not push the drill in too far because you may damage your crown wheel gear, it rotates just above and to one side of this boss area.

Also, as mentioned in a previous post, after tapping is complete you would want to 'flush' it with some lighter-weight oil to make sure you've got all the chips and filings out of the diff.