Technical Eleganza Gearbox Issue

[koalar]

Specified tyres for Grande Punto were 185/65 R15 = 621mm diameter, = 1950mm circumference
Specified tyres for Panda Eleganza were 165/65 R14 = 570mm diameter, = 1790mm circumference
(My standard spec 155/80 R13 = 578mm diameter, = 1815mm circumference)

the punto grande and panda I quoted @ 14% difference were both on the same rim size and aspect ratio

5th gearing were near as dam it the same
the main difference was the final drive

A Punto Grande 1.2 gearbox wouldn't be too bad in a Panda. Its running the same except in a slightly lighter vehicle. Yes it will be revving slightly higher, slightly worse economy

but it doesn't explain why its harder to accelerate 60 to 70 mph post 1. Should accelerate quicker but more noisy

I am obviously missing something

 

[DaveMcT]

Tyre circumference at 1790 to 1815 will not make a difference you will notice. But 1790 to 1950 is 9%. In gearing terms that's huge. It's like having a missing top gear and a first gear that feels like it would climb the alps with the engine switched off.

But the diameter difference is not enough to preclude new wheels. Just be sure to use the same offset (ET) as the original wheels.

 

[jrkitching]

One of the first things I thought of was the difference in rolling diameter between the OP's car and the donor vehicle.

The best tyre information I can find is that the Eleganza runs 165/65x14; most puntos run 175/65x15; that's actually a difference of around 6.3%, certainly enough to explain a noticeable increase in engine rpm at 70mph.

The later ecoPandas are, I think, longer geared; the tachometer in my own Euro4 1.2 reads about 1200rpm at 30mph and 2000 rpm at 50mph, both in top gear; that's equivalent to 2800 rpm at 70mph.

So if the OP is seeing 4000rpm in top at the legal limit, the donor gearbox is significantly different from the one it replaced. I can't imagine cruising in a Panda at 4000rpm being comfortable; it'll sound like the engine is revving its **** off.

If this wasn't properly explained by the garage beforehand, I'd either want the gearbox replaced with one of the correct type, or a full refund.

If the OP does want to continue to use the car in its current condition, I'm thinking this would likely be deemed a notifiable modification by an insurer.