Gearbox help

[steamship]

Originally Posted by HPsauce

Now who might that be?

I think we need her assistance to help with this one. Specifically, other than one being 8-pin and the other 9-pin, what other differences are there, other than visual (the actual switch internals). Is there something about the older 8-pin unit that won't play ball with the newer gearbox?

Can you confirm that the only issue is that the park P light doesn't illuminate and that everything works, or have you not driven it yet (you mention being it the garage).

[HPsauce]

I'm at my limit to be honest, but others know more and will be along in due course. Basically you have a later gearbox in an older car with it's original (older) F125.

It could also be something to do with the gear shift lever as well, are they the same in both cars or not? Or even the TCU...…
(Trying to think what else might be different/incompatible )

[craig]

I did swap tcms so the one in car now is one that came with that gearbox Y729XGA not driven yet I did have prop with starter motor I put the small lead on wrong terminal so would not crank but that has been sorted now cranks but I've as yet to fill her up with all the fluids engine oil. Coolant and power steering fluid but didn't want to as I would have to drain again if I don't get this sorted and I understand there is a process for stearing fluid apart from no light up of p nothing else is wrong fingers crossed won't be running or starting with no fluid just sorting this gearbox first. Do you think I've got to go under and adjust gearbox cable I understand there is not much room for error as getting that in the right place but don't have access to vcds to check and would not know how to do vcds myself hope I'm making sense been on this car for 2 years oh and before I cranked it over for first time I put some misting oil in Cylinders moved it by hand with all plugs out shall turn over at some point with fuel pump disconnected to get the oil circulated as much as possible before start

[steamship]

Okay, ignoring the driven part, can I assume that the park P light worked previously and no longer works? If so, then I'd suggest it has to do with the wiring of the plug. Specifically, the change from the 8-pin to 9-pin wasn't just a case of changing plug format, and the additional wire must be used for something. Again, MJ may be the person who can answer all these questions.

[HPsauce]

Sean, I think (hope) you misunderstood.
My reading is that it's the same F125 switch that was originally in the car, fixed to the replacement gearbox.

So it's the same shifter, cabling, wiring and F125 but the gearbox and TCU have been swapped.

Something in there will be incompatible, but we need someone more knowledgeable than me to comment.
That's why I asked about the shifter on the current and donor cars; are they the same or not (Sport mode etc.)

It would be interesting to see the internal structure of the two types of F125. I've seen several photos of the later version (and can supply them myself if needed) but don't recall any of the earlier one with round plug.
Here's a later type (damaged) which actually has 9 cables internally in groups of 4 and 5. I think the 10-pin plug actually only has 9 pins installed:

[HPsauce]

It would be instructive to see the layout of an 8-pin F125 but my "interpretation" of the 10-pin layout is:
Top 2 tracks, Park and Neutral circuit (with which mine has a problem) used to allow/inhibit starting mainly.
Next 2 tracks, Reverse circuit, goes all the way to the reversing lights so can take quite a load and burn out.
Bottom 5 tracks, detailed gear lever selection position communicated to the ECU, dash etc.

My money is on the lower tracks being different between the versions. So, if anyone has an old F125 internals picture...….

[HPsauce]

And of course there's one on the forum, TOTALLY DIFFERENT inside see here: http://forum.a8parts.co.uk/showpost....8&postcount=17
Cams and microswitches, not tracks. And Audiworld has a better-sized view:
http://forums.audiworld.com/picture....ctureid=166348
It's an interesting bit of total rethink redesign, presumably just to put a bit of extra functionality (and an extra wire) inside what is effectively the same size casing with the same rotating physical input.

I'd put money on it being an incompatibility between the newer F125 switch and older TCU.
Though how you solve it, heavens only knows...…….. Ideas on a postcard please!

Is it worth the risk of putting the original TCU back or would it cause a problem with an older gearbox?

[craig]

W8AND is older than Y729XGA all I did was take XGA gearbox tcm and f125 put them in W8AND but wand is the one that has round f125 so I put that on Y729XGA box they both did work before the gearbox swap so guys and girls am relying on your help 100 percent to get this poor car on the road and to one of the meets its on my bucket list I've waited so long for that moment won't give up

[HPsauce]

Sorry, but I'm genuinely lost. Can you go step by step saying exactly which is which as you go.

[HPsauce]

Trying to reread all you've said and work it out.

Originally Posted by HPsauce

Basically you have a later gearbox in an older car with it's original (older) F125.

Is this correct?

I "think" you are trying to fix the older car (W8AND) with the gearbox from the newer car (Y729XGA).

As I read it you currently have the gearbox as well as the TCU from the newer car (XGA) fitted to the older car (AND). BUT the original F125 is still on AND because it and the wiring loom have the older round 8-pin connector.

Earlier I said

I'd put money on it being an incompatibility between the newer F125 switch and older TCU.

In fact I think I got that the wrong way round. The (older) car you're trying to fix (AND) has an OLDER F125 and NEWER TCU. But they are still incompatible in some way.

My other question needs correcting:

Is it worth the risk of putting the original TCU back or would it cause a problem with a newer gearbox?

but it still stands though, as does the query about the shifters.