SC400 4.27 ratio swap for $125

[spf_lexus]

The SC400 has a decent final drive as is, 3.92 isnt exactly mild but not exactly aggressive either. I was almost perfectly content with my SC down in southern california elevation but after taking it out to colorado at 5000ft it felt like the 500 or so pounds I stripped out was somehow back on the car. Sorta like someone unplugged a single cylinder or something and i was 1 worker shy. Anyway I just read up on forum member Blizzy's post on the 3.27 + torsen LSD swap and realized the facts: Any 1992-2000 sc300 auto automatically has a 4.27 final drive. I did some searching and found out that 4.27 isnbt that excessive... the r32 nd r34 nissan skyline runs a 4.37 final and the 240 runs a 4.11. so this change is substantial but should not be excessive for a street car environment. I did not know about the diff swap until a few days ago but i owned a 95 sc300 briefly and for 225hp it felt just as snappy as the sc400. I will most likely need a real LSD after this swap but kicking the back end on command will be a perk. I drive very short distances 5 days a week so a slight mpg hit is allowable. From what Blizzy states:


-.33/second 0-60mph faster on stock car w/ BFI.
-10% shorter ratio
-79/80mpg at 3000rpm versus 74/75mph at 3000rpm
-155mph top speed dropped to around 135-140mph

I'll be installing the rear end on Thursday or Saturday with lots of pics.

 

[spf_lexus]

Oh yeah heh, forgot to mention but I picked up a used diff + carrier for $125 out of a 100,000 mile donor 93 sc300. Their pretty much guaranteed to be in stock at any junk yard that carries an lexus.

 

[Lextreme II]

There are pros and cons... Keep us updated..

 

[spf_lexus]

There are pros and cons...

I estimate 1-3mpg will be sacrificed but that would be on an otherwise stock engine. My header back exhaust has zero restriction whatsoever, I also run the BFI intake and deleted hydro fa + A/C. I think between the airflow mods and the final drive, I might only see a minimal loss in fuel efficiency if any. If you guys really like the 150mph top speed, this probably isnt the mod for you! Think of it like taking 10% of that top end and move it down to the low end. I figure down the road if the MPG gets too low for my liking, I will attempt a manual swap by then or possibly swap a 5 or 6 speed sc430 trans and tune it with adaptronic, but thats way way down the road.

 

[ruishy1]

so the sc300 has the 4.2 final drive diff ?
im pretty sure the TT also have the 4.2

 

[spf_lexus]

All sc300 automatics have a factory 4.27 and the 5-speed manual has a 4.08 I believe. Stock supra TT has a 3.26 final drive w/ torsen style LSD and the stock N/A supra has a 4.27 like the SC300. I must give forum member Blizzy the majority of the credit since he did all the fact finding and did the actual swap first. But like Blizzy stated, The problem with just swapping in the stock 3.26 LSD is that the ratio will raise top end and hurt low end, 0-60 times etc. I never get my sc up to 150mph, and raising that to 180mph with the 3.26 is counter productive for my goals.

im pretty sure the TT also have the 4.2

Toyota gave the N/A supra the 4.27 because it doesnt have the turbos to help it get up and go and raising the revs will offset the power/tq defecit. The TT supra has plenty of down low grunt so a taller final drive suits it better. No TT ever came with the 4.27. Blizzy took the torsen LSD out of the 3.26 TT diff and swapped that into the stock 4.27 sc300 diff. I did some researching on other high end imports and found that nissan likes shorter final drives. The s13 and s14 240sx runs a 4.10 rear and the r32 skyline runs a whopping 4.37 rear.

 

[ruishy1]

i meant the tt soarer

 

[spf_lexus]

I just finished the swap and drove it home and I can definently feel the difference. Easiest way to describe it is that it drives exactly how my sc did at sealevel, but up at 4500ft Pueblo Colorado. When it gets taken down to sealevel, it should be MUCH torquier, The .33/second faster 0-60mph feels spot on. I am guesstimating that im somewhere in the high to mid 5 seconds 0-60mph at sealevel.

 

[spf_lexus]

This morning I was on my way to school, when a black lowered 325i (pretty sure it was) pulled up behind me and from the menacing stance, I had a good feeling he would be interested in a pull so on green, I gave it everything. I managed to chirp the 255's for a second w/o any brake boosting and I felt one of the strongest off-the-line pulls I have ever felt driving a lexus, this is including my supercharged LS. The power delivery is MUCH more linear without any sags or drops, just a solid, predictable pull. I layed off when the car felt like it was around 90-100mph. The BMW was waaay ahead of the glob of cars that left the light but he never got any closer, I maintained a solid 4 car lead the whole way, and this is climbing uphill on a 15 degree incline at 4500ft elevation. I strongly believe that a well throughtout N/A SC400 can hang with the best of them. Later this afternoon I might get a chance to pull next to my neighbors cammed, 4.10 stang GT. So far im amazed with the $/TQ ratio.

 

[WDoherty]

What all did you end up stripping to lose 500lbs out of the car? Pics, have you had the car weighed?

 

[spf_lexus]

I havent found an industrial scale yet but its around 3100 w/o me in it.

Back seats 34lb
Carpeting + sound deadening

 

[spf_lexus]

I hate this crap, just submitted a half done post and i cant re-edit. Anyway here's my list of weight savings:


Carbon hood w/o hood props 35lb
A/C compressor + extras 30lb
Washer bottle + fluid 25lb
Light weight battery 15lb
Single racing seat 120lb
Hydro fan + reservoir + cooler 15lb
Hydro fan pump 5lb
Gutted trunk (everything) 70lb
Lightweight exhaust 40lb
Lightweight coilovers 25lb
Driving w/ 4 gallons gas 100lb
Cruise control junk + charcoal can 10lb
Stock sub + rear speakers 10lb


I need to drop my 19's for some lighter ones and swap brakes for a true BBK to replace my heavy iron TT brakes but my final goal is to get to 3000lb flat w/o me in it.

 

[spf_lexus]

Oh yeah, I am planning a manual swap next summer and thats good for another 50-60lb over the automatic.

 

[WDoherty]

That is quite alot of things, try to hit up a truck stop with a scale next time your on the way back to Cali so you really know what you got, i did it for fun and the car was 3620 stock with some travel luggage, it cost 8 or 9 bucks.

 

[spf_lexus]

Will do. I think my local salvage yard might have 1. Next month when I grab more parts i'll ask around. I try to weight everything that comes out but a solid number I admit would be nice.

That is quite alot of things,

The interior has the most weight to be cut. The power seats alone can weight up to 160lb total. I bought the car w/ a salvage title and the majority of the interior was so trashed, I wouldn't dare leave it as is so thats why I sorta wqent all out with the deletions.

 

[spf_lexus]

Here is a few pics, it shows how straightforwrd this is. It can be done with just a jack and jackstands but a lift saves at least an hour:

 

[Spinnetti]

Quick Q... SC300 diff work in the LS400 too?

I have a 91 LS400 - will the SC 4.27 diff drop in on the LS400 too?

Thx.

 

[spf_lexus]

Sadly it wont unless your willing to pull out the welder. The eaely LS has 3 mounting points instead of 4 like the sc/supra. You would have to fab a set of mounts for the "wings" that branch off the houssing and bolt to the sub frame. Forum member Hypronet has done it successfully but it required some fabbing.

 

[Spinnetti]

Sadly it wont unless your willing to pull out the welder. The eaely LS has 3 mounting points instead of 4 like the sc/supra. You would have to fab a set of mounts for the "wings" that branch off the houssing and bolt to the sub frame. Forum member Hypronet has done it successfully but it required some fabbing.

Ah, so neither of the SC front "arms" line up with the one hole on the LS? As long as one does, its ok.... I also have metal, a tig welder a lathe and a mill, so can't be too bad ....

Are the internals the same? then I could just swap the guts right?

Thanks....

 

[spf_lexus]

I cant verify if the wings are the same but I im 90% sure the LS mounts shorter than the sc/supra so you would need to re-position the mounts a bit farther out. Check out hypronet's LS400 Turbo thread.. he has lots of pics that show exactly what needs to be modified.

I looked into the "guts" swap and it also wont work. The LS clock is a different size so the only way to make it fit is to make some mounts and swap. Shouldn;t take more than a few hours with the right tools.