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2 Speed Gearbox

Posted: Sun, 25 Jul 2010, 15:10
by Rattrap
I thought automatic transmissions were out of the equation due to their high power losses. They would certainly make the whole gearbox idea simpler if they could be used practically.

2 Speed Gearbox

Posted: Mon, 26 Jul 2010, 03:29
by mcudogs
I am using an auto transmission and from my limited testing it looks like it will work well. It's a 3 speed hydraulically controlled transmission and the torque converter has been removed to increase efficiency.

There are a few people in the USA doing auto conversions and they say the range is not greatly decreased and that's with a torque converter included.

I still have a couple of mods to do with the box before I will be happy with it, but it's OK as it is.

2 Speed Gearbox

Posted: Mon, 26 Jul 2010, 03:39
by EV2Go
By far the greatest parasitic loss is in the torque convertor, if you lock it up or better still remove it all together there is no reason why a well set up auto couldn't nearly be as good as a manual.

Obviously straight cut low drag gears will draw less power, but I believe an auto could be made to work well.

2 Speed Gearbox

Posted: Mon, 26 Jul 2010, 15:29
by AMPrentice
A small jatco can be used behind 600hp with some upgrades.
They are dirt cheap, currently 45aud at pick a part and
better than a manual in my eyes as there is no clunking
or gear synchro issues with adjustments easily made to
suit the rpm required by the individual.

Don can you tell me where you gearbox mods are on your site?

2 Speed Gearbox

Posted: Mon, 26 Jul 2010, 16:10
by Rattrap
AMPrentice wrote: A small jatco can be used behind 600hp with some upgrades.
They are dirt cheap, currently 45aud at pick a part and
better than a manual in my eyes as there is no clunking
or gear synchro issues with adjustments easily made to
suit the rpm required by the individual.

That sounds a lot better than a clutchless manual box to me. I hope to eventually convert my Mazda 323 to electric & i've tried changing gears without the clutch on a number of occasions & found it quite hard & very clunky, not something i'd want to be driving with every day. perhaps i need more practice at it.... Image

2 Speed Gearbox

Posted: Mon, 26 Jul 2010, 20:09
by AMPrentice
The only problem is that there are few car left on our roads with 3 speed gearboxes so might have to settle with 4 speeds in most fwd cases.
I think its worth looking at older cars with bad engines rather than modern ones.
After all the simpler the conversion the better for the first timer.
Best of course is just a big motor, Zeva controller and decent batteries.

2 Speed Gearbox

Posted: Wed, 11 Aug 2010, 17:18
by coulomb
AMPrentice, way back on the first page wrote: How about a modified 2 speed powerglide for RWD?

I was just reading about this on DIYelectriccar. Pretty simple: first, second and reverse. For AC, you'd want to take out the stuff for reverse gear as well, I think. Without the torque converter and reverse gear, they would be fairly light and efficient. They might be a bit bulky though.

It turns out that old Holdens used powerglides. There are 1.82 and 1.76 ratios; the 1.76 were for V8s. Some of them went to 121 km/h in first gear. (BTW, the 1968 Kingswood advertisement on that page is a scream.)

I wonder if these are cheap and readily available because they were once so common, or maybe they get snapped up by racers (they can handle 375 to 750 kW), and possibly classic restorers. You could use one with a column shift, since you'd only ever leave it in drive, or possibly rig up some solenoid or similar for park. (So drive/neutral/reverse/park would be electronic.)

Mechanicals are not my strong point; anyone know more about these transmissions? They would seem suitable for almost-direct-drive conversions.

2 Speed Gearbox

Posted: Wed, 11 Aug 2010, 20:59
by EV2Go
I tried to find actual loss figures but was unsucessfully. People are guessing online at numbers like 30-40% loss for a T400, which I think is very inaccurate since it's 30-40% of what starting figure.

I recall reading a very long time ago that a Glide gave up 17hp, a T350 - 35hp and a T400 - 45hp but I have long since given away my transmission manuals.

Take the convertor out of a Glide, put in a manual valve body for reduced slipage and I could see you nearly halving that figure.

I don't see the T350 & T400 being very viable for electric cars though.

Problem is the PowerGlide was made so long ago now it is getting harder to find a decent one that isn't worn out or been blown up drag racing.

2 Speed Gearbox

Posted: Sat, 14 Aug 2010, 04:31
by AMPrentice
The Jatco is a very good transmission just found the correct ratios
1st 2.600 2nd 1.505 3rd 1.000 Rev 4.100

1st for steep driveways
2nd and 3rd for normal driving

2 Speed Gearbox

Posted: Sat, 14 Aug 2010, 18:31
by EV2Go
Yeah well you can still buy all the tricky mods for them. I was seriously considering a Jatco for my 180sx before it bit the bullet.

The C4 is another of the lighter options. Not sure how they would go in stock form, but you are looking at about $4000-$4500 for a full blown street box.