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Ring & Pinion Swap Stock Differential

13K views 20 replies 11 participants last post by  Kris OK 
#1 ·
So I need a longer final drive and I cannot afford nor want to deal with the difficulties of swapping the Supra/GS430 rear end into my IS300. I've read the thread about swapping the MKIII ring & pinion and it doesn't seem too hard at all.

Has anyone been able to fit a 3.54 ring & pinion into the stock IS300 rear end? It is the tallest one available for the Toyota 8" rear end so I'm guessing it would fit. Anything bigger and it probably wouldn't physically fit in the pumpkin.

So does anyone know if this ring & pinion would work?

Application Guide for Toyota Truck Ring/Pinion Sets and Positractions - Drivetrain.com

If I can get confirmation I'm going to order it ASAP. Any input would be greatly appreciated.
 
#5 ·
It would still be too short with a 3.9 rear end. In 6th at 80mph with a v161 and 3.9 rear end you will be at like 3600-3800 rpm haha.

I'm trying to get my rev limit issue sorted out, I think with a 7400 rpm rev limit with the 3.54 ring and pinion the car will be perfect.
 
#6 ·
Lemme help with a visual aid.

A 3.54 might be ideal. But outside of that, you could also try running a larger diameter tire size in combination with that 7400 rpm rev limitor.

This should put you right at ~124 mph when you run out of gear. What are you trapping currently?
 

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#8 ·
I'm trapping at 122ish right now, give or take 2mph, so I'm right at the top of 5th gear...

I think the 3.54 + 7400rpm rev limit will be perfect! But I need to know if the 3.54 gear will work from the site I posted. Or where I could get one that will work. Jawsgear no longer makes them.

Also did you get my PM TeckIS about the rev limit issue? Your help would be greatly appreciated!
 
#9 ·
Hey did you get this to work buddy?
 
#10 ·
I feel like this is possible. Also look at what I found:

41201-29547 --> EXPENSIVE but its 3.42!

41201-39795 - 3.583:1
41201-29547 - 3.42:1
 
#20 ·
Funny you posted this. I just took my Diff and new R&P to get the 3.58 swap done. I waited a month for new pinion bearings from Amayama Trading, but they finally did come through. I have an AR5, so I don’t think it is as short as a CD009 but doing the math, I’m looking at an 8-10mph difference in 5th between the 3.9 and 3.5. That is huge.

Hope to change out to poly bushings and get it stabbed back in next week. I’ll go easy on it before I flog it, but will update the thread when I do.
 
#21 ·
Ok so just to update. I got my diff back with the 3.58 gearset. It was a new set (they didn’t have any used, and new was only 15$ more) from Nitro Gear, so I am breaking them in. Cruising speed is about 200-300 rpm lower, so that’s nice. It builds boost in 2nd a little better, too. I’ll flog on it more once it’s broken in. So far, I am happy with it.
 
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