Gear Ratios

[JiSingh1]

Hi all,

Looking to replace my gearbox in my Polo.

I currently have a QTR Gearbox, and it broke so need a new one.

I have found an SEP gearbox, but with a difference in the 6th gear ratio, do you know how much of a difference this would make?
Ratios below, not sure which is the driven gear, and which is the drive gear.

02U311349R - change gear - Z=48 - QTR Gearbox
02U311165L - gear - Z=31 - QTR Gearbox

02U311349AA - change gear - Z=53 - SEP Gearbox
02U311165P - gear - 6th gear - Z=34 - SEP Gearbox

Anyone able to figure out the ratios, and if the difference is big, and also if the ECU would detect this change? I know it can cause cruise control issues etc. if it is wrong or not within the spec.

Thanks all.

[2226]

0.6458 (31/48) vs 0.6415 (34/53)

What's the final drive ratio difference?
That is, what's the ratio of the differential?

[JiSingh1]

0.6458 (31/48) vs 0.6415 (34/53)

What's the final drive ratio difference?
That is, what's the ratio of the differential?

Apparently, the Final Drive/Axle Drive Ratio is the same at 58: 16 = 3.625.

All gears are same apart from 6th it seems.

[2226]

I reckon you'll be fine then.
They might have changed the tooth count for durability or some other reason.

[JiSingh1]

I reckon you'll be fine then.
They might have changed the tooth count for durability or some other reason.

Thanks, I was hoping so.

0.6458 on my gearbox vs 0.6415 doesn't seem like a big difference, and the 6th gear is the only difference.
The rest of the gears are the same.
So with that being the only difference, and the final ratio being the same, I am going to hope that the ECU does not detect this difference.

[2226]

ECU don't know squat about mechanical stuff like that.

But it does bring up the question as to why the gears were changed. It could be there was issue with the previous gear set with fewer tooth counts although I don't recall hearing anything about a 6th gear issue. Maybe it is smoother operation or maybe better economy, or reducing stresses at speed.

[JiSingh1]

ECU don't know squat about mechanical stuff like that.

But it does bring up the question as to why the gears were changed. It could be there was issue with the previous gear set with fewer tooth counts although I don't recall hearing anything about a 6th gear issue. Maybe it is smoother operation or maybe better economy, or reducing stresses at speed.

I hoped the same, but apparently the ECU knows the ratios are off, therefore thinks the clutch is slipping, and can also disable cruise control. Something to do with expected road speed & RPM, which is where the issue lies.

Also, from my understanding, just had both boxes running side by side, atleast until late 2017, when mine was cancelled, according to the version of ELSA I use anyway.

Tricky situation.

[2226]

Well it won't be that far off compared to running lower tyre pressures. Then the rpm/speed will be off too. I've had my tyres down (equally) to 2.3 bar before and cruise control worked fine.

Cars are getting too smart/annoying.

[JiSingh1]

Well it won't be that far off compared to running lower tyre pressures. Then the rpm/speed will be off too. I've had my tyres down (equally) to 2.3 bar before and cruise control worked fine.

Cars are getting too smart/annoying.

Makes sense.

It's a case of do I risk it and get it fitted etc. & hope the ecu don't detect any issues, or spend an extra £300 and get the correct one but then be more financially broke for the month, will try figure it out as I need my car back.

[2226]

Fit the SEP. It's the later spec box. I don't see how there'd be issues with such a small difference in ratio.