1.6 FSI 6-Speed idea

Topsie

Member
While i'm well aware that there is a company offering a 6-speed conversion already, I can't help but notice how similar the 6-Speed HBM gearbox is to the GKZ fitted to the A2... Any thoughts?

http://www.ebay.co.uk/itm/Audi-A2-1-6-FSI-5-Speed-Manual-Gearbox-Type-GKZ-/111971038401?hash=item1a11fe74c1:g:ckMAAOSwqbZXEhvx

http://www.ebay.co.uk/itm/Audi-A3-8P-VW-Golf-MK5-Leon-Touran-1-6-FSI-6-Speed-Manual-HBM-Gearbox-/262841443963?hash=item3d3292267b:g:V2YAAOSwNnRYmcff

Hi,

not sure about the fitting, but I checked out the gear ratios a while back and 6th gear on the HBM worked out very similar to the 5th on the A2 5 speed. Thus although there would be an extra gear with closer ratios when compared with the existing A2 gearbox, the new 6th top gear would not drop revs and so give a benefit when cruising at speed.

regards

Andrew
 
How did you work out the gear ratios? 5th speed on the GKZ is a 39/48, the same as 5th on the HBM, with 6th being 36/51. I'm the the difference is in the final drive ratio?

Yes it is... Unless you used the output shaft and differential from the GKZ, but that might drop the 6th gear a little too far.... If I had the money I would genuinely buy a HBM and find out!!!

HBM 6th gear with the GKZ final drive gives about 70mph @ 2800rpm..... Hmmm...

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How did you work out the gear ratios? 5th speed on the GKZ is a 39/48, the same as 5th on the HBM, with 6th being 36/51. I'm the the difference is in the final drive ratio?

Yes it is... Unless you used the output shaft and differential from the GKZ, but that might drop the 6th gear a little too far.... If I had the money I would genuinely buy a HBM and find out!!!

Hi,

I have looked back at my notes and input to output ratio in top (5th) on the A2 FSI is 3.198 where as top (6th) on the A3 FSI is 3.200, pretty much identical. This obviously considers the effect of the final drive ratio as well as the numbered gear.

I also considered options for swapping bits from other 6 speed gearboxes but the A2 gearbox would need a new output shaft and all the other similar 6 speed gearboxes use quite different final drive and primary gear ratios combinations.
Thus, the option would have to be to build a new gearbox using the main housing from an A2 but with all the internals, final drive and end housing from the 6 speed gearbox from another car!

Regarding the output shaft issue above, the company providing 6 speed conversions for A2 petrol gearboxes manufacture their own 6 speed shaft from scratch to match the other ratios used in the gearbox as there is no of the shelf compatible part by VAG.

The closed match on specs I got was the Polo 1.2 TSI 6 speed, e.g. NBU, but I didn't get as far as verifying the casing as being compatible.

regards

Andrew
 
Much appreciated, I had a crazy idea that it would be as simple as pulling the required parts out of the 6-speed and jamming them into the 5-speed casing...
 
Much appreciated, I had a crazy idea that it would be as simple as pulling the required parts out of the 6-speed and jamming them into the 5-speed casing...

Hi,

your idea isn't as crazy as it sounds. There is quite a lot of commonality in the components that are used inside the gearboxes used on different models, the most variation comes from the housing, where it attaches to the engine and also the drive shaft couplings which are removable. The end cover plate which holds the end shaft bearings comes in different versions to allow the same basic design to accommodate 5 or 6 speeds. The 6 speed cover plate bulges out to accommodate the longer shafts.
The 5 speed gearbox used on the A2 diesel models uses a different design framework to the petrol and this one allows the shaft to be extended in situe and the extra 6th speed added on the end. Adding this, a different cover and swapping the selector gate means that 6 speed conversion for a diesel is relatively easy and can be done with the gearbox still in the car.
The 5 speed petrol gearbox's shaft cannot be extended so has to be replaced, requiring the gearbox to be stripped down and rebuilt.

regards

Andrew
 
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