View Full Version : TR4/4A Making an OD pressure gauge - any tips?

01-19-2014, 05:15 PM
Hi guys - anyone ever make an OD pressure testing gauge setup? My A-type OD is not engaging despite being full of oil and manually articulating the engagement mechanism.

I want to make sure I have pressure (or not) before pulling the gearbox. No one down here seems to have one but I'm thinking it can't be that hard to make one.

McMaster Carrr should have all the bits, or so I am thinking.

So, anyone been there and done that?

01-19-2014, 06:06 PM
I made one similar to the gauge shown on the Buckeye site. I presume you are familiar with the excellent articles on the A type OD, including a trouble shooting chart.
Anyway, the gauge is 600 psi glycerin filled. Next, is a 1/4' npt female connector followed by a 3'' length of 1/4" pipe, and finally an adapter-1/4" npt female to 1/2"-20 male. The adapter is an easy lathe project, the other fittings are available from a hardware store or industrial supplier. Or for about $50 you can buy one from Jay Holecamp, who advertises on the VTR site.

Marvin Gruber
01-19-2014, 06:46 PM
I bought one from Jay a couple of months ago. I'd say get one from him to save time ( and money). Plus you know it will be correct.


01-19-2014, 07:53 PM
Like Berry, I made my own. Gauge from MMC, pipe from HD, adapter I turned myself. It was fun; but the end is more than just 1/2-20 threads. The inside has to be bored to the right length, to accept the spring for the operating ball; and the outside has to have the flat sealing surface (where the copper washer sits). Another alternative, if you have a damaged plug, is to braze or weld a tube to the plug.

Lots simpler to buy one from Jay.

Absolute requirement for OD troubleshooting, IMO.

PS, maybe it was just the gauge I got, but when I left it laying flat in the roll away, all the glycerin gradually leaked out. Apparently they are serious about mounting with the threaded end down.

01-19-2014, 08:44 PM
Ditto Jay. Buy his.

01-19-2014, 09:25 PM
I am sold guys, will ping Jay. Thanks.

01-19-2014, 09:52 PM
I should have added that the 1/2" end of the adapter is basically a duplicate of the op valve plug, but only involves drilling the id and machining a square shoulder on the od for the sealing washer.
Your problem with the OD may be as simple as the adjustment of the op valve. Sometimes using the 3/16" rod procedure doesn't provide enough valve lift and it is necessary to move the lever slightly beyond the point where the hole in the lever and od case are aligned.

01-20-2014, 09:01 AM
Thanks Berry, good thought on the lever. When I was staring at the diagrams and the Buckeye site last night it occurred to me that could be it. Doubt I'll get that lucky but worth a shot!