Better auto for an SD1

[DaveEFI]

The chat elsewhere here about upgrading the engine and auto on a P5B has prompted me to start a new thread.

I have an SD1 EFI which would be greatly improved with a modern auto. The original GM TH180 works as well as any other 3 speed - but anyone who has driven a modern 5+ speed auto will know how much better they are in terms of performance and economy.

There are a few articles out there about fitting a 4 speed auto to an SD1, but I'd rather go further and use a 5 speed one. The most common 5 speed auto found in the UK on RWD cars is the ZF 5HP - it's been around since the early '90s. I've had two BMWs with this box and I'm pretty happy with it. It is easily obtained secondhand and cheap - so must be fairly reliable. But has a one piece casing so would need a deal of engineering work to fit the engine - not something I'm equipped to do. The electronics would be less of a problem - there is an aftermarket ECU for just this sort of thing.

The TH180 has a removable bellhousing. Would this mate easily to other later GM boxes? I don't think a 5 speed one made it to the UK - but are plentiful in the US.

Is there a better forum to ask on? Perhaps a US one?

[ChrisJC]

If you do go the 5speed route, I will be interested to hear how you get on.

I rather think that the gear selection strategy for 5 speeds is pretty complicated, and that an aftermarket ECU might not work as well as an OEM setup.

I suspect that is why 5speeds are always electronic, yet 4speed can be mechanical (and sometimes make duff choices)

No idea on mechanical compatibility though...

Chris.

[JSF55]

Have a read here how these went to 4 speed zf box, is there a suitable equivelent to go to 5 speed ?
http://www.stunnedbuffalo.demon.co.uk/gearbox.html

[kiwicar]

Hi
You could buy a GM 4 speed auto and add a gearvendors overdrive tail unit to it to it, it would give you 7 forward speeds, generally theu don't overdrive first, use a simple rev operated switch to switch it in at say 3k revs and drop it out when line pressure tells you you have changed up to the next gear in the auto box.
http://www.gearvendors.com/aghr4s.html
Not cheep but but simple and someone else has done all the difficult stuff!
Best regards
Mike

[DaveEFI]

Have a read here how these went to 4 speed zf box, is there a suitable equivelent to go to 5 speed ?
http://www.stunnedbuffalo.demon.co.uk/gearbox.html

The 4 HP (with RR bellhousing) has many of the problems I wish to avoid - requires considerable body mods.

[DaveEFI]

Hi
You could buy a GM 4 speed auto and add a gearvendors overdrive tail unit to it to it, it would give you 7 forward speeds, generally theu don't overdrive first, use a simple rev operated switch to switch it in at say 3k revs and drop it out when line pressure tells you you have changed up to the next gear in the auto box.
http://www.gearvendors.com/aghr4s.html
Not cheep but but simple and someone else has done all the difficult stuff!
Best regards
Mike

The snag is there's isn't a 4 speed GM which is a direct fit - unless I'm mistaken. Before the vast cost of that unit.

I'd be quite happy with 5 speeds.

[kiwicar]

Hi
I don't think you will find any modern boxes with a bell housing for the rover engine, when the engine was designed GM were phasing out that bell housing pattern to go for the BOP patten I think Rover were the last to use it by some 30 to 40 years. You will either have to use an adaptor between bell housing and engine or between bell housing and gearbox, don't forget the early range rover autos used the torqueflight 3 speed, that bell housing might bolt onto a more modern case.
I would seriously look at the US 4,5 and 6 speed boxes by the way, there are going to be many more aftermarked controllers for those boxes and nearly all of the 5 and 6 speed boxes are controlled by electronics.
Best regards
Mike

[Eliot]

Have a read here how these went to 4 speed zf box, is there a suitable equivelent to go to 5 speed ?
http://www.stunnedbuffalo.demon.co.uk/gearbox.html

I bet he could tell us how to run a chevy in a P38

[DaveEFI]

Hi
I don't think you will find any modern boxes with a bell housing for the rover engine, when the engine was designed GM were phasing out that bell housing pattern to go for the BOP patten I think Rover were the last to use it by some 30 to 40 years. You will either have to use an adaptor between bell housing and engine or between bell housing and gearbox, don't forget the early range rover autos used the torqueflight 3 speed, that bell housing might bolt onto a more modern case.
I would seriously look at the US 4,5 and 6 speed boxes by the way, there are going to be many more aftermarked controllers for those boxes and nearly all of the 5 and 6 speed boxes are controlled by electronics.
Best regards
Mike

Indeed. The 3 speed GM box as fitted to later SD1s has a removable bellhousing. What I don't know is whether that fits later GM 'small' boxes which I believe were based around the same design. The snag is they are rare in the UK - the last RWD Vauxhalls used Asin Warner boxes. But common in the US - even BMW used them in some models, where they used ZF in the rest of the world.

The electronics side may well be fixable - even MegaSquirt do an aftermarket one. But it's a pretty complicated business sorting out one of those from scratch on an unknown box. Far more so than fitting EFI to an engine not originally made with it.

[kiwicar]

Hi Dave
I think the real answer, if you want a multi speed modern auto, is to transplant an engine auto box combination from a vehicle of a similar weight. I knew Megasquirt were working on a controller, but I stopped going on the site a couple of years ago, I felt there was alot of bullying on there and went off it and lost touch. The performance of a modern box is 90% down to the controller and how it interfaces with the engine, look at the jag, the controol unit for the box even controls the throttle during a change they are completely intigrated into the engine managment.
What I am saying is even when you have the engine and box bolted together you only have half the job done, you are then into a big "mapping" job to sort out the gearbox change pattern under many circumstances.
Best regards
Mike

[CastleMGBV8]

Have a read here,

http://forum.britishv8.org/read.php?6,19311

And this also,

http://forum.britishv8.org/read.php?6,15171

Kevin.

[Eliot]

Have a read here,

http://forum.britishv8.org/read.php?6,19311

And this also,

http://forum.britishv8.org/read.php?6,15171

Kevin.

Fooking hell - complete tranny in the lathe!

[DaveEFI]

Have a read here,

http://forum.britishv8.org/read.php?6,19311

And this also,

http://forum.britishv8.org/read.php?6,15171

Kevin.

Thanks - even more food for thought.

[badger]

Maybe worth consideration also, based on some earlier comments - the BMW 330d uses a 5-speed auto (AL5D80 or something like, in BM-speak)which is a GM derived box.....
"Real-world" RPM limits are similar, as are the torque curves (compared to a modern 16v 4-cyl rev-box) so it may be an option as it's quite a compact unit.

[DaveEFI]

Maybe worth consideration also, based on some earlier comments - the BMW 330d uses a 5-speed auto (AL5D80 or something like, in BM-speak)which is a GM derived box.....
"Real-world" RPM limits are similar, as are the torque curves (compared to a modern 16v 4-cyl rev-box) so it may be an option as it's quite a compact unit.

Yes. Also, GM boxes are common on other BMWs made for the US - the E39 528 at launch had a GM 4 speed there while it had the ZF 5 speed in most of the rest of the world. Never did work out why. The 330d box is probably an Aisin made one.

It's more important for me that it is small enough to fit without hacking the bodywork about. I know the ZF 5HP18 as fitted to UK BMWs is. There is also an aftermarket ECU available for that box. And it's readily available and can be modded for more torque. But would need an adaptor plate between box and engine, or a cut and shut using part of a bellhousing for a RV8. As well as lots of other stuff.

I actually have collected an Aisin Warner 4 speed from a Vauxhall Senator - that has been used for this. A 4HP22 from a Rangie, and the RWD bits for that. A 5HP18. And a spare TH180 which is the current fitment. I also have a spare engine, so would mate things up off the car.