Auto gearbox identification plates

[johnnydog]

Having just checked my auto gearbox identification plate on my 73 125bhp 2.5 PI following a query from Tinsmith_Skippy (Ross Taylor), I was surprised to see that it appeared to have a 'lime' green coloured id plate. I couldn't make out the prefix numbers/ letter due to the limited access and dirt up there, but I will clean it up and have another look over the weekend.
Assuming the official workshop manual is correct, a PI should have a red id plate, and a light grey/ green plate indicates it's a 2000 box.
The question is - what detriment is there, if any, of using a 2000 auto box in a 2.5 PI, and has anyone any experience of using a 2000 auto box in a PI or vice versa. I appreciate there is more torque / power coming from a PI engine, but will a 2000 box take it without any problems?
Thanks

[Tinsmith_Skippy]

Hello John the plate on your Pi gearbox could be correct, the plate on my Pi is also green and ours are the same year. I’ll have to check the serial numbers but off the top my head the 2000 is a 3EZ Green and I don’t think this box has that number. I’ve also read in the manual the plate on a Pi should be red With 7EZ. I bought a spare box which as you mentioned a 13 EZ Blue plate which has come out of a carburettor 2500 as I’ve found out the filler tubes are different. So that’s the conundrum!

[johnnydog]

Thats good to hear Ross - I was thinking that at some stage I might end up changing the box!! I have quite a selection of good used autoboxes from a variety of cars I have scrapped over the years, but I didnt make note of the id plates.
I have a 1969 Mk2 auto PI that I am debating whether to fully break or not - be interesting to see what box is in that. It drove ok when I got it and I have no reason to think it isn't the original.
Is the official workshop manual wrong then? (wouldn't be the first time !!)

[Tinsmith_Skippy]

If you wouldn’t mind having a look at the 69 Pi because these auto boxes didn’t come with the car. The previous owner wanted the car to be a manual so he bought a manual overdrive box and ancillaries to do this. This is very annoying as I’m trying to put the car back to original and the auto box wasn’t with it. The 13EZ I bought from a chap and he said it was from a Pi but it ain’t because a carburettor filler tube was fitted. But definitely the box is geared up for a 2500. The other box was salvaged from a Pi that someone was scrapping, so at the time I had first hand knowledge where it came from. I bought the engine and gearbox but I did notice a refurbishment automatic company sticker on the car so this could be why the numbers and plate colour are wrong.

Either way currently the 13EZ Box is going on anyway unless someone has a 7EZ red plate box out there.

[johnnydog]

Hi Ross,
I will check the H reg PI gearbox id code (with interest now!) over the weekend. So I may have the wrong gearbox in then.....
And I may just check the other boxes whilst I'm at it so that I know what other boxes I actually have
It would also be handy to know the thoughts or experiences of other PI auto box owners...
Watch this space....

[Tinsmith_Skippy]

My engineering tutors classic phrase let’s look at the first principles, How does work

https://youtu.be/u_y1S8C0Hmc

https://youtu.be/bRcDvCj_JPs

So are there differences between the 2000 box and 2500?

The clutch’s could be different the torque converter multiplication factor and the planetary gear ratios.

Looking at the manual under automatic transmission the differentials are different a Pi being a 3:45:1

Reading further MK1 Pi transmission had L position rather than the Mk2 1-2-D selections so the Red Plate 7EZ could be this box.

Hmmm can anyone add anyone more thoughts?

[johnnydog]

Looked at both videos Ross - very interesting. I got the second one re the torque convertor, but the first one - well, I understood the basic principles, but then it went a little over my head (rather quickly!)
So the original question about what the differences are still remain....
Maybe 'harvey' on here, who has a lot of auto gearbox experience, may be able to shed some light on it. I shall probably send him a PM...

[harvey]

There will be differences between different Series of boxes. Generally series runs with numbers and letters are early boxes, (very early boxes just have 2 letters), and the lower the number the earlier the box. The later boxes are all number series. The rather strange thing is that on the BW35 AFAIK all the numbers are odd, there aren't any even ones.
There are 2 diameters of converter, and 2 types, with and without a cooler on them. All the clutch plates are the same, but the number of plates vary between 3-5. I'd guess both 2000 & 2500 had 5 plate clutches. There are 2 different gearsets to my knowledge, and 3 selector patterns, PRNDL, PRND2D1L, & PRND21, but there are also variations on how those selector patterns work in practice. For example on the Triumph with the PRND21 pattern, "2" allows the box to shift 1-2 and 2-1, but locks out TOP, but on the Rover "2" gives SECOND gear start, and it won't change out of SECOND, it stays there until the lever is moved. This has the advantage that on uphill starts in "2" the car can't roll backwards.
There are 3 diameters of front servo, and 2 types, manually adjusted and auto adjusted. and two types of rear servo, but you'll be lucky to see an early one, same as rear pumps, there aren't many of those left either, and AFAIK they were all on 5 position selector boxes on the Triumphs.
There are so many other differences I couldn't begin to list them, or even know them all, but from the factory they would have been different, if only in some minor way. Add to this that boxes could be getting on for 60 years old (introduced in 1961) with various overhauls along the way, there's no way of knowing exactly what would have been inside originally, and what relevance what's inside now has to that.
As for the PI boxes which I think were the origin of the questions, ISTR they had different springs on the shift valves to delay the upshifts a bit to make them more "sporty". Good luck working out which springs are in there as none of them are marked for identification purposes.

That's about all I can think of ATM.

[johnnydog]

I managed to check the two auto gearboxes this evening, with surprising results.
The '73 125bhp Sienna Mk2 PI with the lime green id plate has an all number prefix '452' followed by the stamped in serial no.
The '69 132bhp white Mk2 PI has a mid blue id plate with the prefix 13EZ followed by the stamped serial no.
It appears then from the info harvey gave in his very informative post that the both boxes have been replaced with later types - the 452 is a very late box, and the 13EZ is from a later 2500.
I can find no info however as to what model the 452 box was originally fitted to when new.
The water just gets muddier and muddier....!!

[harvey]

I can find no info however as to what model the 452 box was originally fitted to when new.

According to the paperwork I have it just lists that as 2500 10/68-05/74, but I can't say I've ever seen BW35 boxes with even series numbers, but, with over 200 different series numbers to my knowledge I can't know them all. If it is the case, trust triumph to be different....
My data also has the 13EZ as fitted to a 2500 running the same dates but I would have expected an "EZ" box to have been upgraded and upgraded to an all number series, which then probably did run through to 74 before being replaced by the 65.