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[Andy H]

OMG! We're drilling holes in the gearbox casing now.

What can possibly go wrong? 😀

Lots

Measure twice, cut once.

If you haven't cobbled together one good gearbox using two old ones before then you might want to ask a responsible adult to supervise......

[Kevin Wood]

No need to cut any holes. Just get some old connectors of both types and make up some adaptor cables.

PM on its' way, Shackeng.

[Lazydocker]

No need to cut any holes. Just get some old connectors of both types and make up some adaptor cables.

PM on its' way, Shackeng.

Exactly this

[Shackeng]

Yep, this was my plan. I propose to fit the old receptor plugs in the new box, provided that they fit the holes, and as both connectors in reality have only 4 working wires in each, I will splice 'new' Omega type connectors into my existing harness, thus preserving the existing plugs should another box change be necessary.
If anyone is breaking an auto Omega I need the two connector plugs plus a foot or so of wiring tails on each.

[Shackeng]

Digressing slightly, Mr Gav has sent me the servicing requirement for the Senator box:

The transmission fluid should be changed every 36k or four years, which ever comes first.

Capacities are drain and refill   2.6 litres
After removing the large sump  4.7 litres
From dry                               6.4 litres

Very interesting if they are referring to the same box that I have, as the Omega is 'sealed for life'.

[Shackeng]

Well unfortunately, the old plugs do not fit both the holes in the new box. The 4 pin from the old box above the small sump moves nicely into the required position above the small sump in the new box, but the 7 pin plug is too wide. The ideal solution would be to ream the hole out from 22mm to 26mm. In the meantime I'll try to track down a suitable 6 pin connector to fit.

[Shackeng]

Further info regarding the internal wiring. On the old box, what I thought was 2 wires from the multi pin plug in the large rear sump connected together inside the box, is correct, however they are connected together via what appears to be a very small resistor about 2mm long. This is all inside a plastic sheath, so difficult to determine exactly what type it is.
In the new box, a similar resistor is connected between the plug and the earthing lug inside the small forward sump.
Could these be temperature sensors of some sort?

[Andy H]

I can read a temperature for the gearbox using my scan tool. I assumed that there was a sensor in the oil flow somewhere

If all the other wires are connected to solenoids then I suppose the mystery component must be the temperature sensor.

[Shackeng]

I can read a temperature for the gearbox using my scan tool. I assumed that there was a sensor in the oil flow somewhere

If all the other wires are connected to solenoids then I suppose the mystery component must be the temperature sensor.

It's the only reason I can think of, and there is one in both boxes, albeit in different sumps, and which is the reason for the connection problems. I'm hoping Kevin will enlighten me.

[Shackeng]

Update. I was able to swap the 4 pin plug from the old box into the correct, forward small sump in the new box in place of the 6 pin plug, so the internal harness will transfer from the old box with it. However, the rear sump mounting hole in the new box is 4mm too small to take the 7 pin plug (6 only in use) from the old one, 22mm instead of 26mm. Ideally I would just have the hole in the box reamed out to take the plug, however, as only six pins are in use I am hoping to find a suitable 6 pin plug of 22mm dia. which I will then incorporate into the existing internal harness, or get an auto electrician to do it for me. I will then splice the appropriate external connector onto my car loom.
Currently the new box has its temperature thermistor in the small sump and utilises the unused, in the Omega, ground (earth) spade lug that some of you, like me, may have puzzled over in the sump. The Omega AR25/35 has its thermistor in the large rear sump joining two of the pins on the 7 (6) pin plug, so straight in and out of the box just sampling the temp. with the thermistor.
Onwards and Upwards. and many thanks for all the support I am receiving on this project.

[Shackeng]

Incidentally I suspect this is what would normally fit on the end over that rubber O-ring and snake it's way up the rest of the firewall on the Senator: http://www.ebay.co.uk/itm/FILLER-TUBE-for-AR25-AR35-AUTO-GEARBOX-Senator-B-/360283397015

If you really want that easily accessible fill tube, maybe that could be bodged modified to fit the Omega firewall.

Showing my confidence that I will get this going, I bought the above for a tenner in the hope that it will fit down the side of the engine in the TD. Especially as it was recommended to change the ATF every 36k in the Senny box. It certainly looks as though it will fit, and thanks for suggestion Aaron.

[Shackeng]

Assuming that the wiring problems are overcome, is the fact that the reverse ratio is different : Omega=2.00:1, Senny 1.92:1, likely to throw up any warnings?

[Scatmancraig]

This is a fascinating read.  I had half an eye on that box you had bought (I'm also an ABS member), I'm almost glad I didn't bother now as it sounds like a lot of work you're having to go through.  Not that there's too much wrong with the AR25 in my TD, yet.  It's a bit slow engaging reverse, but other than that its ok.  I've got the filter and gaskets so it'll be getting a good service in a week or so.

Looking forward to further updates on your work!

[Kevin Wood]

Assuming that the wiring problems are overcome, is the fact that the reverse ratio is different : Omega=2.00:1, Senny 1.92:1, likely to throw up any warnings?

I doubt it. Reverse is selected manually with no involvement of the ECU.

[Shackeng]

Unfortunately I am getting nowhere with my search for a suitable 6 pin connector to fit to the old harness and then fit the 22mm hole in the rear sump,  and may have to consider the option of reaming out the hole to 27mm (not 26 as previously stated) to accept the 7 pin plug from the old box.