KC95SC400

iTrader: (3)

Many of you probably know about this mod, but there doesn't seem to be too many people on this forum that have done it.

I originally found the thread on Supraforums but here is a very good writeup on how to do it. http://www.lexusclub.co.uk/lsocautoboxmod.pdf

I'm hoping to do this within the next couple of weeks. Seems like a no brainer to me. Shim the 1-2 and 2-3 accumulators to quicken the shifts and turn the adjustment screw on the valve body to up the line pressure. Should take a few tenths off on the track AND actually make the auto last a bit longer.

I have not had any real problems with my trans, even at 320++ rwhp (have installed headers, full 2.5 inch exhaust and a smaller pulley on the Vortech since I was on the dyno last). The biggest problem I do have is that the trans doesn't shift fast enough at WOT causing the engine to bounce off the rev limiter, not good for going fast and probably not good for the engine or the transmission. I have the throttle cable that goes to the transmission about maxed out, this does help but it still bounces. Also, the engine retards timing during shifts to make them smoother, it is said on Supraforums that the quicker shift eliminates this, since it shifts too fast for the ECU to respond.

I do not intend to go too aggresive on the shims, likely about a 1/4 inch, seems to be what the Supra guys like. I already have traction problems when downshifting so I don't want to go crazy. I just want a tight 1-2 and 2-3 shift. I SHOULD be (based on 1/8 mile times) in the high 12's in the 1/4, a few tenths saved on shifting might get me into the mid-high 12's.

Let me know what you guys think. If anyone has done this, please share.

KC

Punky

iTrader: (4)

Sounds like it will work well. Getting a modded 1uz into 12's would be so great to see, as most people just swap. When I get more done to my 1uz I am thinking about this mod too. Would be happy to hear your results

Ian300D

Where do you plan on getting the shims. I've been eyeballing this for a while, as it's one of my only complaints on the SC400. That and the no aftermarket DIN.

Teflon Don

Bedlam lives down the road from me. Ive been in his car with modded auto and it shifts alot faster.
The shims are basically made from ally and can be made up easy enough. Jobs messy but not difficult. If you've got access to a ramp/pit, it will be alot easier.

goodluck bud

SC400TT

iTrader: (4)

Looking forward to seeing your results on this mod KC. I am curious how this will perform, hold up and compare overall to the BL built tranny I paid for.

Keep us posted...

Ryan

KC95SC400

iTrader: (3)

I hope it will work as well as I think it will. I MIGHT actually be in the high 12's now, haven't run the quarter since the headers and exhaust, just 1/8 mile. There's a new track right down the road from my work which should be open for test and tune nights soon. The NHRA nationals kickoff event is this weekend, I'll be there Sunday.

I'm still researching but it appears that most people just stack up some flat washers. 20-21 mm wide, stack enough to shim the desired height.

Thanks for the info and thanks for the good luck! I work in a shop and have all the needed tools and a lift, check my sig pic.

I have had a couple of valve bodies off in the past to replace solenoids and such, mostly on Camry's. The worst part is usually the mess, chances are I'll end up with trans fluid in my armpit at some point. LOL.

I imagine it will do well. I haven't had any real problems out of the auto yet. Upping line pressure and making the shifts faster should only make it last longer. If it ever dies on me I'd likely rebuild it with the good stuff myself.

I imagine your power levels are WAY higher than mine though, the BL tranny should be a good investment for you. I'm surprised you haven't decided to go 5 or 6 speed yet.

---------------------------------

So I should be doing this soon, within the next week or two. I would have been able to do it today (slow at work) but I had to order the filter. I'll keep you all posted.

KC

93MSB

iTrader: (8)

I started this project last night, the pipes were a little stubborn coming out. Im in the process of attempting to find a solid shim, otherwise ill probably just stack washers.

Im also going to order the deep trans pan and hopefully they can get me the o-rings for the accumulators.

ill post my results when i finish which will likely be next week sometime

KC95SC400

iTrader: (3)

So, I actually did it yesterday. So far I'm not impressed. I stacked washers (20mm width) 4 high which came out to 7.62mm for each accumulator (1-2 and 2-3). Everything seems to be working as it should. Very slight increase in shift speed and firmness part throtte, still bounces of the rev limiter (the problem I was hoping to fix) between 1 and 2 shift.

The adjustment screw looks a bit different on my valve body, it only actually has two spots for adjustment. I turned it in anyway past where the adjustment stops are, pushing the valve into the valve body more. Should be doing the same thing.

I've read the unplugging the no 1 speed sensor will stop the rev bounce, I'm trying a little expirement, I'll post with more info later.

I will likely end up adding a few more shims later. When I have the valve body back down I'll double check that I didn't damage the gasket the first time although I'm pretty sure it's fine. Probably wouldn't be a bad idea to replace the accumulator orings.

KC

TheRonTom3

iTrader: (5)

this interests me since i have decided to keep my 400 auto now that i have a nice little rwd 5 spd

KC95SC400

iTrader: (3)

Ok, noticed a change I didn't notice right away. Seems to shift down through the gears quite a bit faster. Say your going 30mph in forth and you slam it, it goes third then to second (or first) faster than it was.

The other expirement I mentioned. I've read that disconnecting the no 1 speed sensor wire improves the rev bounce from 1-2. Problem with not having a number 1 speed sensor is that you'd then have an inoperative speedometer. Also possible issues with trac, abs and who knows what else. Well, I was looking at the wiring diagram and noticed that the signal wire for the no 1 speed sensor goes through the combination meter and THEN to the ECU. So, rather than disconnecting the sensor I cut the wire from the combination meter to the ECU. I still have a speedo and so far no problems with anything else, no blinking lights, nothing.

And...it seems to have very much helped the bounce problem. It's wet out and nearing rush hour traffic time so I didn't get to thrash as much as I would like but there definately seems to be less bounce and delay on the 1-2 upshift. Gonna leave it cut for now until I can drive around a bit more.

Will still likely throw in a couple more shims next week. I wonder if the Lexus accumulators are bigger / hold more fluid than the Supra ones, could be why the difference isn't very dramatic.

KC

Punky

iTrader: (4)

Do you mind me asking why not just buy a supra TT auto and rebuild it?

IS_250

iTrader: (2)

probably bcuz washers are much cheaper?

KC, keep up the good work... you should be a sneeze away from 12s now..

LexusFTW

iTrader: (7)

The SC400 and Supra TT are the same transmission minus the longer 1st gear in the SC.

http://www.clubna-t.com/forums/showthread.php?t=2932

http://www.clubna-t.com/forums/showthread.php?t=4145

IS_250

iTrader: (2)

now i remember reading that on the na-t site, but can the stock SC4 auto tranny be used on a 1jz or 2jz with the right bellhousing?

sorry for gettting off the topic.

LexusFTW

iTrader: (7)

All the info is there about the bellhousings and output shaft. But to answer your question, no. The SC400 is electronically controlled where as the 1jz auto is more like the 2jz-ge auto which is line pressure controlled with the clutch packs of the SC400 auto.