Gbox & Diff setup for Drifting use

smbbob

smbbob

New Member
Hi all! Hope im posting in the correct place.

So my question is this, I currently drive a Supra MK4 (410 whp) , weight down to 1280 KG ~ , wisefab all round, and using a 330d Gbox with a 4.1 Ratio Diff.

A major issue i been having is that gearing have been closing very early on each gear, 4th gear is only getting me to 110 km /hr on 7000 rpm.

The question is this, Whats the difference in either changing the Gearbox to a longer ratio box or changing the diff to a 3.2 ratio?

Does it really matter which 1 you change? I assumed that changing the diff to a Longer ratio is better since it wil get more loaded with torque and if it gets broken on track its much easier to change a diff rather then a gbox. Not sure if im on the right track tho!

Thanks in advance for your help! :)
 
MaccyD said:
Top of 4th at 60mph though seems like youd be wanting a new diff rather than gearbox as youre so far out. WIth that much power you probably dont even use 1st-3rd lol.

This is a useful tool to help you get some more details.

http://www.bokchoys.com/differential/e46_gear_ratio_calculator.htm
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Ye i used that before and came with the below results, i was just wondering if at the end if the day changing the diff or changing the gbox would be the same or different.

1st 2nd and 3rd are useless yes !

265/35/18 Tyre
7000 rpm
4.11 3.2 Differential
Gear km/hr Gear km/hr
1st 39 1st 50
2nd 71 2nd 90
3rd 113 3rd 145
4th 160 4th 207
5th 205 5th 263
 
Well i guess it points to diff being out. Though im no expert. But it seems like you need a major shift in the ratios. If there arent any other BMW boxes that will drop straight onto your conversion then i guess look at what diff ratios are out there.

It does seem oddly miles out. I know on JZX the ratios arent amazing but they are perfectly usable.
 
MaccyD said:
Well i guess it points to diff being out. Though im no expert. But it seems like you need a major shift in the ratios. If there arent any other BMW boxes that will drop straight onto your conversion then i guess look at what diff ratios are out there.

It does seem oddly miles out. I know on JZX the ratios arent amazing but they are perfectly usable.
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Ye its totally shitty gear ratios for drifting at least.. I just found a Lexus ls430 Diff with a 3.22 ratio for 120 gbp. Think im gona give it a try!
 
smbbob said:
Ye its totally shitty gear ratios for drifting at least.. I just found a Lexus ls430 Diff with a 3.22 ratio for 120 gbp. Think im gona give it a try!
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Definitely your best bet, and like you said, you can easily swap a diff at the track compared to a gearbox, yes I know its possible but still a lot easier changing a diff than a gearbox

hope the 3.2 works for you as your gearing does seem really out haha
 
Bu11et said:
Definitely your best bet, and like you said, you can easily swap a diff at the track compared to a gearbox, yes I know its possible but still a lot easier changing a diff than a gearbox

hope the 3.2 works for you as your gearing does seem really out haha
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Just hope the 3.2 will widen the gear ratio enough. Since the Ratio calculator online only widen the gears up to 15-25 km /hr on each gear. Not sure if it will be enough :/
 
What size tyres do you run? Do you have scope/budget to increase a size or 2? Or drop your rear pressures - that will also help and give you more grip
 
Bu11et said:
What size tyres do you run? Do you have scope/budget to increase a size or 2? Or drop your rear pressures - that will also help and give you more grip
Click to expand...
Already running 265/35 18" mate :( using achilles 123s. Now switching to Splendid tire(basicaly same grip)

Minor parts like increasing from 17 to 18 inch wasnt noticable. Major parts such as diff/gbox needs changing. 3.2 Diff should arrive next Thursday, hoping for a much better result !:)
 
smbbob said:
Already running 265/35 18" mate :( using achilles 123s. Now switching to Splendid tire(basicaly same grip)

Minor parts like increasing from 17 to 18 inch wasnt noticable. Major parts such as diff/gbox needs changing. 3.2 Diff should arrive next Thursday, hoping for a much better result !:)
Click to expand...

Switching from a 4.1 to 3.2 you'll definitely notice a big difference! Just depends if its enough like you say
 
Hi all!

For all you guys wondering about this thread, I finally tested the 3.2 ratio Lexus diff, and it worked PERFECTLY.

It made all the change needed for my setup!

Highly recommend a 3.2 ratio diff with a 530d e39 box!

MN0_3316.jpg
 
Bu11et said:
nice one mate! Glad its sorted! is 2nd gear useable now? haha
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To be honest every gear is usable now.. Pulling of on 1st is gaining me alot of tracti on 2nd gear ,so gaining a lot of speed and 3rd gear is a total smoke machine atlast while gripping up on 265 tires. Never thought how much of a dofference this would be! :D
 
Hello there guys!
currently i'm working on my project car and couldn't complete it without any help. I have a Cressida Rx70 with 3uzfe automatic 5 Speed transmission probably a650e. when i got my car running i broke my driveshaft 2x times ! i don't know its because of stock Cressida differential its ratio is like 9/43 (4.7) maybe? can anyone help? do i need to change the diff? car revs alot in 4th and 5th gear :(

IMG_2725.PNG
 
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