Correct gearbox??

[panda8290]

Hi guys, help please.

I have just a had a reconditioned gearbox and clutch fitted to my mk3 gti 8v '97. How can I check if the correct gearbox has been fitted for the engine spec? I checked the speedo againsy my tom tom this weekend and at 30 its reading 35 and at 70 its reading 81. I am concerned that the wrong box has been fitted hence the speedo showing much higher.

Is it possibe to re-calibrate the speedo?

Would the mileometer also be reading incorrectly?

Any help/suggestions would be appreciated.

Thanks Andy

[zollaf]

had you checked the readings with your old box, if so what were they?

[panda8290]

Sadly not, I'd only had the car a week before the gearbox seized and to be honest not done many miles or got a feel for the car at all !
The car does seem low geared, a lot of wheelspin in 1st and 2nd if not careful.

[SammoVWT]

Dont forget the manufacturers 'downgrade' the speedo because of A safety, and B they dont want their brand to be caught on cameras speeding a lot.

Also, you might want to check wheel diameter.

If the wheels are bigger, your speedo may be saying 30, but actual is maybe 35, vice versa for small.

It does seem a fair bit off at high speed though.

[panda8290]

Thanks Sammo - the wheels/tyres are standard and correct. I hear what you say about the speedo and agree the manufacturers over-state but at 100mph on my speedo, gps was reading 86mph. Something not right I fear.

[SammoVWT]

DKM Might be able to help you out, hes got like every mk3 gearbox listed with ratios somewhere.

Seems like your long ratios are out anyway in the upper gears thats for sure!

[DropKickMurphy]

Hi Panda,

do you know what the gearbox code is on the one you have fitted at the moment? the code can be found ounderside of the bellhousing. i believe the one which would have been fitted originally would have been a DFQ which has the following ratios:

1st - 3.445:1
2nd - 1.944:1
3rd - 1.286:1
4th - 0.969:1
5th - 0.805:1

final drive - 3.667:1

if you could let me know the RPM and gear you are in when you are doing 30mph and its reading 35 that would be good, or even better if you could let me know how fast the speedo is reading when you are doing, say, 2500rpm in 4th i can work it out from there. also the wheel diameter; tread width and aspect ratio all help (i guess its 205/55/15)

basically, it sounds like a shorter-ratio gearbox has been fitted, which isnt hard since the AGG came with the longest ratio 'box fitted to Mk3's. this isnt necessarily a problem, since the speedo is over-reading but obviously it would be a lot easier if you could see what speed you were ACTUALLY doing!

it is possible to recalibrate a speedometer, and this would be significantly cheaper than buying an identical gearbox to the original and removing your current one and putting the DFQ in its place. how you go about recalibrating a speedometer is something which i'm afraid i dont know.

if you can let me know a bit more i can identify the exact box you have fitted, or alternatively look at the code on the bellhousing and you will know for sure.

DKM

[Housemaster300]

DKM is the daddy when it comes to gearboxes ha ha

[panda8290]

Thanks very much DKM, you certainly know your boxes!!
I will firstly try and identify the gerabox from the bell housing and then get some speedo/tacho/gear info. Might not be today but watch this space.
Many thanks again, much appreciated. panda

[panda8290]

Hi DKM,
I've looked for any ref marks on the bell housing and I'm afraid I cannot see any obvious code.
I have checked speeds/revs as you suggested:-
4th gear
2000rpm 40mph speedo
3000rpm 60mph speedo
4000rpm 78mph speedo
3rd gear
2000rpm 30mph speedo
3000rpm 44mph speedo

Tyres are 195/50/15

I hope this info helps in sorting out where my problem lies !
Many thanks AL