Differential Gear for Track and Daily Driver

[stig]

Hi all,Just got a Getrag 220 with a 5th 1:1 gear ratio. Been reading this thread and saw fabianyee's recommendations. I think I might go for a 3.91 for a daily driver and occasional tracking. Just a bit concerned on the highway RPMs :stupid:Anyone with the g220 on their e36s mind sharing their setups and final gear ratios? Also the RPM at say 120kmh? TIA :top:!

 

[tehyw]

take 3.43 lah... lose a bit of pick up tak ape... will 3.43 can lifted from e30/e34(m20) fit e36 ?

bro, year of ur car pls.

 

[stig]

12/1996 318i auto sedan... Suppose to have come with the m43 engine but my dad blew it up while I was away :stupid:

 

[loafer]

I'm using a Getrag 220 on my E36 with 3.15 rear diff. I believe my 120km/h is somewhere around almost 3k rpm. I think so la. Later tonight I'll keep an eye on the rpm and report back.

 

[ALBundy]

3.91 with a 1:1 final drive is a little high in my opinion. I wouldn't go any higher than 3.64 and 3.46 is the best in my opinion.

cheers

 

[fabianyee]

stock 318i shud be running with 3.45... so a 3.64 or 3.73 would be good enuf

based on calculation,
3.91 : 120kph at about 3500RPM
3.73 : 120kph at about 3400RPM
3.64 : 120kph at about 3300RPM
3.45 : 120kph at about 3100RPM

 

[stig]

stock 318i shud be running with 3.45... so a 3.64 or 3.73 would be good enuf

based on calculation,
3.91 : 120kph at about 3500RPM
3.73 : 120kph at about 3400RPM
3.64 : 120kph at about 3300RPM
3.45 : 120kph at about 3100RPM

Hi guys,

Thanks for the responses so far. Did a little testing with the auto tranny and found my 110 to be slightly below 3k (pic attached). I certainly don't mind 3300-3500 rpm in this speed. Kinda like the high rpm notes

Based on fabianyee's data, I think a 3.73 or a 3.91 is what I'm aiming for for 120kph with 3500 rpm. After all I don't plan to kena saman much these days so I think the high rpms will deter me.

 

[loafer]

120km/h for me is around 3200-3300rpm.

 

[tehyw]

stock 318i shud be running with 3.45... so a 3.64 or 3.73 would be good enuf

based on calculation,
3.91 : 120kph at about 3500RPM
3.73 : 120kph at about 3400RPM
3.64 : 120kph at about 3300RPM
3.45 : 120kph at about 3100RPM

how do you calculate this?

 

[IanDaddy]

this BokChoy has a lot of info on diffrential

http://www.bokchoys.com/differential/GearRatios.htm

 

[stig]

Here's a good tool I found: http://www.fatboyraceworks.com/gears/ . Used it to compare differentials

Going with the 3.91! :top:

 

[vincent]

for track use and road use 3.45 is good enuff for a 318i. not to high as you need to think of driving on highways as well

btw if im not mistaken 318i is using 3.38 stock and 318is is using 3.45

 

[stig]

for track use and road use 3.45 is good enuff for a 318i. not to high as you need to think of driving on highways as well

btw if im not mistaken 318i is using 3.38 stock and 318is is using 3.45

Which transmission was the 318i using? I'm getting a Getrag 220 with 1:1 fifth gear and 3.91 diff.

My current setup is an auto tranny with 4.44 diff.

 

[vincent]

Yes same gearbox , 4.44 is a autobox diff , too high even gymkhana also not so suitable for manual . Just get a 3.45 will do you will love it. my e36 318 manual with m43 engine 1.8 with 3.45 is good .

e36 manual gearbox is the same ratio in the gearbox itself untill 328 manual . the diffrence is the flywheel size , 318 8.5 inch , 325 9 inch , 328 9.5 inch .
318 diff will be good if use 3.45 ori diff is 3.38 , 325 is using 3.15 rear diff , 328 is 2.93 recomemded but use 3.45 will be great for track and autoX .

 

[stig]

Yes same gearbox , 4.44 is a autobox diff , too high even gymkhana also not so suitable for manual . Just get a 3.45 will do you will love it. my e36 318 manual with m43 engine 1.8 with 3.45 is good .

e36 manual gearbox is the same ratio in the gearbox itself untill 328 manual . the diffrence is the flywheel size , 318 8.5 inch , 325 9 inch , 328 9.5 inch .
318 diff will be good if use 3.45 ori diff is 3.38 , 325 is using 3.15 rear diff , 328 is 2.93 recomemded but use 3.45 will be great for track and autoX .

Ok I had to did a double check and found the chart I posted above is misleading. Here's the link I used to double check the ideal RPM at 120kph (75mph): http://www.angelfire.com/fl/procrastination/rear.html

With a 3.91 diff: 3950 rpm @ 75.045 mph
With a 3.46 diff: 3500 rpm @ 75.144 mph

Looks like I have to reconsider ... Thanks!

 

[unstopables_7]

**sorry off topic guyz**
i'm on e36 325 manual and i am looking for 3.15 diff urgently coz currently running very high on rpm..
anyone have it PLZ pm me to sell swap or anything..

 

[tombstone]

good thread to lock onto

 

[ALBundy]

Ok I had to did a double check and found the chart I posted above is misleading. Here's the link I used to double check the ideal RPM at 120kph (75mph): http://www.angelfire.com/fl/procrastination/rear.html

With a 3.91 diff: 3950 rpm @ 75.045 mph
With a 3.46 diff: 3500 rpm @ 75.144 mph

3.91 is way too high and you will lose top speed. The highest I would go would be 3.64 but 3.45 would be the best.

Cheers

 

[ezzo369]

sorry guys may i chip in...... may i know how well and reliable an auto gearbox (GM 4spd) would be if i turned on the sport mode for a couple of laps in the circuit? keen to join the pasir gudang trackday this 17/7 but worry i will trash my gb. thx in advance.

 

[fabianyee]

sorry guys may i chip in...... may i know how well and reliable an auto gearbox (GM 4spd) would be if i turned on the sport mode for a couple of laps in the circuit? keen to join the pasir gudang trackday this 17/7 but worry i will trash my gb. thx in advance.

It all depends on the current condition of the gearbox and the ATF, and how hard u planned to drive on track..
If just driving slightly faster and harder than how u normally drive on spirited runs, it shud be ok. but if u're whacking it like u're Ayrton Senna all the way, then keep ur fingers crossed that the car will be fine after that.

Be forewarned that the track surface is rough, so don't go into corners too hot. Slow in fast out, so that the car doesn't understeer unnecessarily. Otherwise, u'll be changin tyres after the few laps... Drive it smooth and u'll still be fast and be able to conserve the tyres. Drive it rough and u may not be faster but for sure u'll hurt the tyres..