stockhatch

iTrader: (12)

I ran the W58 for a while before the GTE swap. It was bad NA too. Overgearing a weak car does not make it more fun, trust me, I have overgeared several cars and was slow to learn the lesson, but it did finally sink in

With that said, it is cheap and easy enough to swap rear ends, so I encourage you to do it and learn for yourself. I'm not trying to come off harsh, but you sound pretty adamant about doing it anyways.

I don't even blame you for it, since I am much the same way. I want to try something and decide for myself, despite the naysayers.

KahnBB6

iTrader: (5)

Thank you That is the way I am as well with figuring out unconventional ideas on my own. The tone of a few of the replies have just taken me aback and that's probably what you're reading in my own replies.

I've asked the same questions on a thread I made on SupraForums it's a very different atmosphere there. Their nearly identical MKIV NA's came with 4.272 final drives and suggesting that I'll change an SC 5-speed's final drive isn't such a big deal there. The most I was asked was if I planned to go turbo. I said no and that was that. Supra NA 5-speed owners don't seem that concerned about having a 4.272 final drive ratio until they want to go NA-T or swap their cars.

So, yes, I plan to go ahead with it along with installing a TT Auto LSD. Other than a custom exhaust system this will probably be the last of my performance modifications. I'm not trying to win races with this car, just have fun with it. To me, slightly tighter gearing is fun. Since it was a factory Supra configuration that was sold to the general public I'm sure I'll be fine as long as I understand the few tradeoffs involved. I've driven more aggressively geared NA cars before.

Most people turbocharge these cars so I understand where they are coming from. An SC is a cruiser to most people. To me it's just a slightly heavier Supra NA 5-speed with different skin that happens to be a lot cheaper and less attention-getting than the real mccoy.

Da Coupe

iTrader: (7)

I agree with stockhatch. Sometimes you have to try it out for yourself to see if YOU like it. Well if you do decide to go that route I have one sitting in the garage. And I'm local.

KahnBB6

iTrader: (5)

Well, I picked up a 4.272:1 rear diff today thanks to Da Coupe



It will get a thorough restoration and cleaning especially on the rear cover then some de-rusting agent and a coat of black paint on the rest of the pumpkin.

Then, in it goes. For now I am holding off on finding and swapping in a Torsen but that is next on the list regardless of which pumpkin stays in the car.

KahnBB6

iTrader: (5)

After a bottle of simple green, a lot of scrubbing with wire brushes, using 150 grit sandpaper (and more simple green) on the aluminum cover and some Rustoleum Rust Reformer to prep the surface:



Now it's prepped for painting

I called everywhere in town I could find asking for a pint of black POR-15 or black Hammerite but no company seems to carry either brand of rust-encapsulating paint so I ended up ordering a pint of POR-15 from their website.

It's just mindblowing that no retail hardware or paint supply carries either of these.

KahnBB6

iTrader: (5)

The diff repainting has been completed for several days now. I have pictures which I will update here tomorrow. The POR-15 works amazingly well with a prepped surface!

I have to order a 12mm hex socket online for the rear diff bolts. Again, it's amazing that something so simple isn't available locally.





I also found this handy calculator:

http://www.solemnwarning.net/speedo/?

It takes into account not only the gear ratio change but also the tire diameter change. Since the car came from the factory with 215/60R-15's I started with that and the 4.083 ratio. My 275/40R-17's currently make the car under-read by 2.00%. With a 4.272:1 axle and the 275's it will over-read by 2.57%. Not great but I can live with that temporarily until I can get a Yellow Box to correct it. Am I correct in assuming that the digital odometer gets its sensor signal from the transmission just as the speedometer does?

I was given a spare companion flange to swap onto the diff in order to make it fit my SC driveshaft. I am still unsure if I actually need to do this but I've read enough to understand I don't want to do it incorrectly lest I affect the internal preload of the pinion. It takes a very deep 35mm socket from what I am reading.

UPDATE: after some more reading it seems that the flange on the diff is 111mm, so I must use the other 101mm flange provided.

KahnBB6

iTrader: (5)

More parts...



It's from a 1994 TT Auto and I've verified it has a Torsen.

I nearly did the 4.27 swap a couple of weeks ago but the axle bolts were torqued on much more than the factory 64 ft-lbs. A single one was so tight that it stripped. Thankfully it didn't prevent me from bolting everything back together and driving the car. I ordered a few handful of OEM axle bolts and I'm looking to get the seized and stripped bolt removed and replaced soon. Then I can start over.

So far it's looking like it's a rare thing to find a shop that swaps differentials in L.A.

KahnBB6

iTrader: (5)

I found a shop last week. After talking to FSR Motorsports they recommended Driftmotion, who in turn recommended a diff and axle guy they use a lot.

account2x

iTrader: (5)

It took me an hour to swap out a differential with the basic tools. Air Gun, Breaker Bar, Harbor Freight allen socket set, Floor Jack, Torque Wrench. If you need help just ask.

KahnBB6

iTrader: (5)

Thank you for the offer! It's not just the pumpkin, though. I am having the 4.272 ring and pinion from the Lexus automatic diff swapped and re-shimmed into the 94 TT Auto Torsen pumpkin. That is what I'm having Driftmotion do for me.

Then I'm installing it. It's taken a back seat for now though since I just got "randomly chosen" (yeah, sure...) to get a Test Only smog this year. I wasn't supposed to be due until next year.

I'm figuring out if I need a new main cat this week. After that I'll start on the diff.

KahnBB6

iTrader: (5)

I dropped off the 4.272 Open and 95 Supra TT Auto Torsen diffs at Driftmotion today to get the swap underway. It should be done in a few days. I'm keeping the 3.769:1 ring and pinion for the future but I'll be using the finned Supra carrier for the swap.

scshinobi

iTrader: (3)

what does this GR limit the top speed to? 145-150ish? It is good for city cruising but anything over 50 mph just sucks. Makes you want to throw it into 6th

KahnBB6

iTrader: (5)

EDIT: Theoretically with the 275/40-17's I have currently it should be 155mph at 6800rpm. With 255/40-17's it would be 151mph. On Supraforums the 5-speed NA people claim around 148mph realistically before you start hitting the rev limiter. I doubt I'll take it that high up anyway.

It won't suck any more than a stock Supra 5-speed sucks over 50mph. With the 4.083 in fourth it's a slug until you hit 65 mph. Downshifting to 3rd helps but I feel like it needs the 4.272 gears to pull better. My last car, a Prelude, ran at 3500rpm in 5th gear at 70mph. Yeah, I felt like it needed a 6th gear too but it had all of its pull on the highway and I loved that about it. I hated the low end acceleration, a problem the SC has to a far lesser degree due to its torque. Less aggressive gearing in that car would have been totally unacceptable.

As long as my car is NA I think it will be fine. Then again, I drive my SC like it's an old muscle car rather than a cruising luxury car if that is any indication as to why a 4.272 would appeal to me.

KahnBB6

iTrader: (5)

I picked up my rebuilt TT Auto diff this afternoon from Driftmotion in Montclair, CA. The 3.769:1 ring and pinion were set aside. 4.272 gears were in good shape. Torsen was fine. All new seals. Replaced totally shot carrier bearings. New rear pinion bearing. Swapped on the smaller SC companion flange.

I'm going to repaint the pumpkin in POR-15 black over the weekend. I was going to wait until I had a Yellow Box V4 before I installed it but I'll probably put it in and buy that later.

I'd show a picture but it looks exactly the same as before.

DoomLight

iTrader: (3)

a lot of useful info packed into this thread. good read. least i know i can get away with using a sc400 pumpkin on my 1jz with r154 swap.