Is it possible to tell what's the gear ratio?

[seewai]

Dear sifus,Is there a way with only the speed-and-rpm data, and brand of tranny, that you could "guess" the gear ratio?5sp Getrag, manual, is all I know, couldn't find any labels to tell what model it is.4th gear 2500 rpm = 80kph5th gear 2500 rpm = 100kph5th gear 3000 rpm = 120kph5th gear 3500 rpm = 140kphI'm on an E39 M54B25 now.Appreciate your expertise and guidance!Cheers.

 

[Vincent Hor]

Seewai, did you change your rear diff when you did the converion? I am not an expert with manual tranny, but it does seem your engine rpm is a bit on the high side.

 

[V-Man]

http://www.johnmaherracing.co.uk/gearcalc.htm

 

[fabianyee]

If I understood you correctly, u're using a 5 speed Getrag manual gearbox???
If yes, the 5th gear ratio is 1:1...

As for the rear diff (final drive) ratio, there is a tag on the rear cover to indicate the ratio...

based on the info u posted, the final drive shud be between 3.15 - 3.45...
the speedometer isn't all that accurate and change of tyre size would the indicated speed.

 

[seewai]

Bro Vincent: The workshop claimed they did change the rear differential. Yes it does feel much higher, as though it's still running on auto tranny rear diff.

Bro pardypeople: Thanks for the useful link.

Bro fabianyee: Yes it's a 5sp getrag manual gb. It's the rear differential that I'm referring to. I'll try to look for the tag soon and see what I can find. You are right about the rim size and speed thing, I'm on 17" so I guess there shouldn't be much noticeable difference right?

Cheers.
seewai

 

[Vincent Hor]

Seewai, the metal plate should be attached to the rear diff. If it's missing you can still make a rough guess by rotating the prop shaft to see how many turns of the prop shaft takes inorder for the drive shaft or wheel to make one complete turn.

 

[fabianyee]

u might want to read this other thread as reference: http://www.bmwclubmalaysia.com/foru...-Differential-Gear-for-Track-and-Daily-Driver

 

[mrbig]

i Have seen the label some where b 4 ... dont remember where but will sure try to find a sample & post it up for you hope this will help & i am sure i will be able to get you an ori e39 manual 525 chasis number for you to do a cross reference. hope this will help bro see wai & i am not sifu !!!!
: )

Dear sifus,

Is there a way with only the speed-and-rpm data, and brand of tranny, that you could "guess" the gear ratio?

5sp Getrag, manual, is all I know, couldn't find any labels to tell what model it is.

4th gear 2500 rpm = 80kph
5th gear 2500 rpm = 100kph
5th gear 3000 rpm = 120kph
5th gear 3500 rpm = 140kph

I'm on an E39 M54B25 now.

Appreciate your expertise and guidance!

Cheers.

 

[seewai]

Came across this and I think it's nice.

[video=youtube;i_Enyf67KTs]http://www.youtube.com/watch?v=i_Enyf67KTs[/video]

 

[mrbig]

Seewai, the metal plate should be attached to the rear diff. If it's missing you can still make a rough guess by rotating the prop shaft to see how many turns of the prop shaft takes inorder for the drive shaft or wheel to make one complete turn.

sorry guys e39 diff dont come with "metal plate" anymore ! metal plate only for older models.

 

[mrbig]

sorry guys e39 diff dont come with "metal plate" anymore ! metal plate only for older models.

see image below..it a label / tag.. this is just a sample .. see 2.35 far top right.. now thats the ratio label....

this was taken from a e46 320d manual.

Hope this answers your question See Wai

Cheers

 

[seewai]

Thanks MrBig, however there's no tag left in my case.

see image below..it a label / tag.. this is just a sample .. see 2.35 far top right.. now thats the ratio label....

this was taken from a e46 320d manual.

Hope this answers your question See Wai

Cheers