UZinator

iTrader: (1)

I finally got my 92 onto the road. And I am not ready to do my manual swap yet. It may be several years off. So until then I am stuck with the auto slushbox. I have found that the gearing totally sucks.

First gear is extremely lacking. When the RPMs come up -it is finally beasty like I would expect. But that first gear really blows.

So I started looking around at other 1UZ trans options. I found that the SC is supposed to have the below gearing:

A340E:
1st:2.804, 2nd:1.531, 3rd:1.00, 4th:0.705

A341E:
1st:2.531, 2nd:1.531, 3rd: 1.00, 4th: 0.705

And here is a 98 GS400:

A650E:
1st:3.357, 2nd: 2.180, 3rd: 1.424, 4th: 1.00, 5th: 0.753

Has anyone attempted the swap? This looks like it would really give a lot more to the SC for those that want to stick with the auto trans. So does anyone on here know of anyone that has done this conversion?

Also -since the GS has steering wheel shifters -this could also open up something new to the pre-98 SC's if it hasn't been done. I think I am going to pick up a GS trans and give it a try.

Thanks for any help in advance.

t2d2

iTrader: (8)

I found several things in a quick Google search, this being the most informative:

http://www.lextreme.com/forums/showthread.php?t=13881

This one says the A650E was used in the '98+ SC400. Is that right? I know it went to a 5-spd A/T.

I'd love to see a relatively easy A/T upgrade path for the SC400, eliminating that performance bottleneck without the complexity and cost of a Manual swap.

UZinator

iTrader: (1)

I am hoping that somone has already done this and can do a How-to for it. It can't be really all that difficult if the mounts are the same, the overall length and the driveshaft yoke are all the same.

I would guess that if there is a trans controller computer that it wouldn't be too hard to wire it in with either a GS400 partial harness or building a custom harness. I haven't looked yet to see if the controller is is seperate or internal to the ECU like some other cars.

It does look like the 98 and up SC400's did have the A650E. I have wired in some functions of an alternate ECU before (two ECUs in one car) for a digital dash and so I think I can do the same for a trans.

I started wondering about this because a friend at work was complimenting me on the SC and told me that he had a 98 GS400. I asked him if it had that same slugishness that the 92 SC has and he said no. He said it had buttery smooth gears and tons of power. Those gears would explain it. They are about 200% better than the 92 SC gears.

UZinator

iTrader: (1)

Well -I decided that I am going to find out. I am so facinated with the gear ratio of this transmission that I went out and pulled one today. So far into this project I have $120 or so including tax. I am not sure how this will play out -but I have the Gs transmission and I also have a SC300 differential that has the ultimately low gearing.

Between that and the much lower GS first and second -it should turn a somewhat stock SC400 into a complete beast (in theory). I have limited slip to compliment the arrangement as well. I will post up a How-to when I have it done so that others can do similar if interested. I will also post up the info and pics on installing the LS into the SC300 diff.

Hopefully my theory about all of this is correct!

t2d2

iTrader: (8)

I'm definitely following along with interest!

alltrac

The A650E appears to be plentiful and reasonably priced. I looked on car-part.com and 400-500 seems to be the average price. Looks like any Rear Wheel Drive Lexus from 1998-2005 used this trans. However, getting even more interesting is the A761E, the 6 speed auto from the 2006-2007, SC, GS, LS, 430. Don't know the physical size/length of this trans, but could be very well compatible as the late 400 and 430 cars used the A650E. This one has it all, low 1st gear, 1st-4th are close, 5th (.72) is a simiar overdrive, and 6th (.58) is a BIG overdrive.

alltrac

Looks like controlling the transmission would be the problem. Hardware is the easy part. Making the hardware work is another story.

UZinator

iTrader: (1)

For me -I think the electronics part is easier because I am getting too old for the physical work part of huffing transmissions in and out and busting knuckles in the process.

It looks like the drive shaft needs to be swapped because the yoke on the 650 is a fixed type rather than a slip spline like the 340. So that isn't a problem. And if I do have to wire in the later model ECU for transmission control only -I will post up the how-to on that. But first I am going to investigate to find how much change it would take to have the 92 ECU control it.