6 speed gear box replaced with 5 speed

anna_conda

No, I didn't notice any difference. Mind you, they'd had it so long and I'd been driving their bitty 1.2 Polo courtesy car, so anything felt better than that. There's definitely no 6th gear!

Thanks for all the replies.

Strider590

On a technical note, the cars ECU will have been programmed to deliver power to match the gear ratio's in the 6 speed box. Meaning performance will be compromised with the 5 speed box fitted.

anna_conda

Well, I have complained to them, and they told me that they'd done it because they thought I'd have less trouble with the 5 speed! In fact the person I spoke to was awful and decided he didn't need to speak to people like me! Very intimidating. Spoke to trading standards and am writing letter today.

Really wish I'd kept my 10 year old banger that I traded in!

C_Mababejive

This is very clear. They did not fit the right replacement gearbox. They need to do the job again if you can trust them. Mind you,if they pull a stunt like that,they must be rubbish anyway. Name and shame.

Hammyman

Strider590 wrote: »

On a technical note, the cars ECU will have been programmed to deliver power to match the gear ratio's in the 6 speed box.

Err, no unless it was one of the new smart semi-autos.

Strider590

Hammyman wrote: »

Err, no unless it was one of the new smart semi-autos.

It times gone by, gearboxes were matched to engine characteristics.... These days it's the same, but the engine can fine tuned using the ECU to get an even closer match.

I'll use an example, Ford's old type 9 gearbox has a very low ratio 1st gear, the reason for this was being mated to the Ford Pinto engine in the old Sierra, this engine had a lot of low down torque and combination of torque and low first gear ratio made pulling off with heavy loads (or towing) much easier.

Take that gearbox and put it into a 600kg kitcar with a race tuned kent/x-flow and that first gear becomes a complete joke.... You find you have to "short shift" into 2nd else you'll be bouncing the valves and sitting in a cloud of tyre smoke not going very far.

In production vehicles, the gearbox and engine are very carefully matched and it cost millions of £ to do so.

rodenal

I dont agree with ecu programming for the new box tbh, the 5 speed should work fine just bolted in there. Regardless you didn't ask for it and it wasn't what you were sold so get trading standards involved and put some pressure on them.

The kit car reference doesn't make sense to me - you match the box to a well matched diff and the ratios are taken care of

Would be different if you had actually requested a 5 speed box if you had read they were stronger or something along those lines.

Mankysteve

The whole point of having the extra gear if that it gives you better fuel economy at motor way speeds as your not straining the engine as much. Switch to five speed is just craziness, they did because a 5 speed is cheaper simple as that really. Yes you can fiddle around the the ECU a bit but you'll still loose that extra economy.

Strider590

Hmmm look, the purpose of more gears is to lower the gear ratio's so that you don't run into flat spots.


Example:

Power band = 3'000rpm to 5'000rpm

Your accelerating away and you hit 5'000 rpm, you change up to the next gear, but this drops your RMP to 2500rpm, you've hit a flat spot where you can't access the engines power until you hit 3000rpm again.
You struggle along for a few seconds until 3000rpm and then away you go again (this is not a desirable characteristic if you imagine being half way into an overtaking manoeuvre)

So what's the solution? you change the gear ratio's so that changing gear at the trailing edge of the power band leaves you in the leading edge of the power band after the gear change.

If your power band is too narrow, you have little choice but to start adding gears.
Having the luxury of more gears therefore makes it possible to tune the engine to produce MORE power within a smaller power band. Hence why slapping on a 5 speed box is going to affect performance.

Explained quite well here although for bikes

" An engine tuned to ride on the track will produce peak power within a narrower band, higher up the rev range. If the gear ratios are not adjusted, the engine revs will drop below the power band at each gear change, and therefore the motorcycle will not accelerate as fast as it could. "

Any questions?

Flyboy152

anna_conda wrote: »

After several weeks, I finally got my Golf TDI back from the dealer I purchased it from. Problem was a complete gearbox failure, but happily car was still under warranty. Drove off happily enough, and a bit later noticed that I had a new gear stick, and surprise, only 5 gears. Going back tomorrow to complain, but I just wondered if any of you have any opinions on this. Must lower the value of the car if nothing else. Any sage advice gratefully received.

Is there actually six gears there and they have just fitted the wrong insert into the gear stick? Citroen had a problem with this on C5s a few years back and they all had to have replacement discs put in the gear knobs.