GSR gearbox weird ratios

[gerryeddie]

Wondering if anyone has any idea on something that is doing my head in.

GSR with Evo engine but standard GSR gearbox - W5M332NRBE. Gearbox has been rebuilt and individual gear tooth counts have confirmed it to be stock standard GSR gear and transfer ratios (the top speeds mentioned below never changed before or after the gearbox rebuild so nothing funny went on with that)

205/40/17 tyres.
Redline at 7850rpm
2nd gear max speed ~86kmh
3rd gear max speed ~142km/h

These speeds have been confirmed by ECU logging, GPS speed app, speedometer, and just seat of the pants the ratios feel much shorter than a normal GSR gearbox.

How is this possible? How can stock ratios still be acting like it is a short ratio gearbox?
From memory with a previous GSR, 2nd gear should get to over 100 and 3rd should make it to about 160? Plugging the ratios and tyre/rpm into an online calculator it also suggests second should reach over 100.

What the hell is going on?

 

[khubner1]

whats rpm at 100? in 5th

 

[CLuTZ]

http://www.4gtuner.com/topic/16116-speed-rpm-5th-gear-ratio/

 

[BMGTZ]

I note you have counted the gears etc...but have the crown wheels/ pinions been changed to 3.909? stock gsr =3.545

 

[gerryeddie]

Yeah everything was counted to be identical to stock GSR.
I've attached below the actual tooth count while the box was apart.



Haven't checked RPM's in 5th at 100 for a while but from memory it was about 3500rpm @ 100, maybe more. Certainly screaming at 110kmh.

 

[BMGTZ]

if its all stock ratios..it should be the same as any gsr. Unless your clutch is slipping

 

[gerryeddie]

Yeah that crossed my mind too, but it recently had an old clutch replaced with an ACT 2900 which should be way overkill for the amount of power its putting out at the moment and it hasn't changed between clutches. There doesn't seem to be any slipping. Have done multiple 30kmh to redline WOT 3rd gear logs and it pulls cleanly without any unusual variations in revs.

Is there any other potential variable? Some weird driveshaft setup? I just don't get it.

 

[Cranked]

A shot vcu?

 

[EVO-00X]

Nope. If its physically the GSR ratios and FDR and Transfer and Diff ratios, then there is no possible way it should be doing the same speed as EVO.
It might seem its doing the same speed but chances are it actually isnt.
Have you checked that you have a GSR speedo drive in the gearbox? A GSR speedo drive is black in colour.
Check the pic out, It's easy to remove. Just unscrew the speedo cable, remove the one 10mm bolt and pull it out.

 

[caged]

Yeah mine does about 3900rpm at an indicated 120kph, which i checked on gps last week to be around 124kph. So yours sounds similar to mine which is on 215/40/17s

 

[gerryeddie]

Hmm you might be on to something. So it has a 180kmh cluster I assume from the donor Evo 1 back when the conversion was done by a previous owner. Is the speedo drive meant to match the gearbox or the cluster? Ie should it have a GSR speedo drive because it is a GSR box or the Evo 1 speedo drive because it has the Evo cluster?

 

[khubner1]

Your spedo drive ahould be matched to your final drive