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(Post Link) post #1 of 12 Old 05-01-18 Thread Starter
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Question about Alfa 147 gearboxes

Hi! First my plan was to fit shorter first gear from 1.6T.S. in my 2.0T.S. gearbox (or if it is easier to fit fifth gear from 2.0 in 1.6 gearbox).

Now I'm thinking about fitting first and fifth gear from 1.9JTD 116HP in 2.0T.S. gearbox. Does anyone know if this is possible?

Screen shots are taken from Alfa Romeo 147 2005

https://www.alfaowner.com/Forum/attac...823346&thumb=1
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1st off the Diesel 5 speed box is not the same platform as the 5 speed petrol boxes, the only similarity is the bolt pattern to the engine block. The Diesel 5 speed shares the same platform as the 6 speed box. The mods are slightly prohibitive to go that route... I did the 6 speed (2.5 gear internals) conversion on my race cars and it was A LOT OF WORK.

In the 5 speed boxes gears 1 - 4 is all in one section of the input / output shafts and difficult to swap about. The 5th gear is a bit easier to swap, so yes 5th gear of the 2.0 on a 1.6 box makes more sense.

EDIT: 5th gear is the same on the 1.6 and 2.0 - the difference comes in with the Final drive ratio. 1st gear on the 1.6 is shorter AND the bigger final drive ratio on the 1.6, making it significantly shorter than 2.0 1st gear. If you want to restore the longer 5th gear - you need the 5th gear from an Uno Turbo of 0.875:1 (they where popular in SA) - even the Fiat 20V coupe has the same 5th gear, just a shorter final drive - making overall ratios longer. I would fit the 1.6 box and live with the slightly short 5th gear

Last edited by Gertie; 08-01-18 at 08:32.
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(Post Link) post #3 of 12 Old 15-01-18 Thread Starter
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Do you maybe know on how much rpm on 120km/h will go with Uno turbo/Coupe 20v fifth gear
2.0T.S. gearbox?
1.6T.S. gearbox?

Is there going to be some problems with speedometer if I swap 1.6 gearbox?
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The math is easy; the ratio changes from 0.92 to 0.875, so the rpm will drop by the same ratio.

147 and 156 speedometer work from abs sensors, only tire sizes can affect speed calibration
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(Post Link) post #5 of 12 Old 30-07-18 Thread Starter
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It's been a while

I bought gearbox from Alfa Romeo 147 petrol, 120HP. If you want shorter final drive don't by gearbox from 105HP because it is the same gearbox like on 150HP.

I also bought fifth gear from some 1.9TD gearbox. it is straight fit into 1.6 / 2.0 TS gearbox.

Number of tooths 1.9TD fifth gear: 43/33
Number of tooths 147, 1.6 120HP fifth gear: 37/34
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What is the end result like?
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(Post Link) post #7 of 12 Old 29-10-18 Thread Starter
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Sorry for late answer. For now i only fitted 1.9td fifth gear in 2.0 twin spark 147 gearbox. It is great for highway, 120km/[email protected], 180km/h @4500rpm. On lower speed @60km/h in fifth gear, the motor loses its elasticity a little bit. But @70km/h and above everything is fine. Soon i will fit 1.6 gearbox with shorter final drive and this diesel fifth gear.

Edit: I'm on 215/40/18 tyres. So on 15" or 16" wheels is probably everything better. And engine is much more quieter on highway.
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Quote:
Originally Posted by _Petar_ View Post
Sorry for late answer. For now i only fitted 1.9td fifth gear in 2.0 twin spark 147 gearbox. It is great for highway, 120km/[email protected], 180km/h @4500rpm. On lower speed @60km/h in fifth gear, the motor loses its elasticity a little bit. But @70km/h and above everything is fine. Soon i will fit 1.6 gearbox with shorter final drive and this diesel fifth gear.

Edit: I'm on 215/40/18 tyres. So on 15" or 16" wheels is probably everything better. And engine is much more quieter on highway.

What is your advise if I would like to set up and change my 147 2L 150hp factory spec gearbox ratio & final drive for track/circuit driving? Thanks in advance.
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Quote:
Originally Posted by flavalava View Post
What is your advise if I would like to set up and change my 147 2L 150hp factory spec gearbox ratio & final drive for track/circuit driving? Thanks in advance.
Normally track use benefits from lower gears and closer gears, but it really depends on the power delivery curve of the engine and the track itself.

A friend of mine and I have the same gearboxes and limited slip diff on turbo 2.0TS cars. His boost comes in VERY STRONG at 4000rpm through to red line, mine starts at 2500rpm and climbs to 5000rpm. He complained 2nd gear is to short coming out of the slow sharp corners, where 3rd bogs down. I don't have that problem, but his car does make more power than mine.

Normally aspirated cars are more predictable and linear, best advice would be to test the gearbox you have now and make the call.

With my previous normally aspirated set up and 5 speed box, I touched 2nd gear in corner 2,where the rest of the lap was purely 3rd and 4th gear. Now with a 6 speed gearbox on and turbo boost, I use 3 and 4 mostly and touch 5th on the back straight. Still not touching top gear around the track.

I restate that there is no best solution from this side of the screen. It will be best for you to give us feedback on your experience, then we could advise.

Last edited by Gertie; 25-11-18 at 12:19.
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Originally Posted by Gertie View Post
Normally track use benefits from lower gears and closer gears, but it really depends on the power delivery curve of the engine and the track itself.

A friend of mine and I have the same gearboxes and limited slip diff on turbo 2.0TS cars. His boost comes in VERY STRONG at 4000rpm through to red line, mine starts at 2500rpm and climbs to 5000rpm. He complained 2nd gear is to short coming out of the slow sharp corners, where 3rd bogs down. I don't have that problem, but his car does make more power than mine.

Normally aspirated cars are more predictable and linear, best advice would be to test the gearbox you have now and make the call.

With my previous normally aspirated set up and 5 speed box, I touched 2nd gear in corner 2,where the rest of the lap was purely 3rd and 4th gear. Now with a 6 speed gearbox on and turbo boost, I use 3 and 4 mostly and touch 5th on the back straight. Still not touching top gear around the track.

I restate that there is no best solution from this side of the screen. It will be best for you to give us feedback on your experience, then we could advise.
Thanks for the reply Gertie. The track that I go to is Sepang Circuit in Malaysia (as attached).

Forgive me if i'm wrong, but I believe that the factory spec gearing are high. specifically 3rd/4th gear. I believe that it is very long for this circuit. And I also feel that the car can benefit from having a higher final drive (4.1/4.3 or above). I couldn't get into 5th gear on the main straight. If i remember correctly, 4th gear can't be fully utilized before braking into Turn 1. I could benefit from fitting in 16" wheels, but my BBK doesn't allow that.

If I wish to change to shorter gearings, how do I do so as I don't have much info on which car models are interchangeable in terms of gearbox, ratios and etc.
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Last edited by flavalava; 26-11-18 at 05:58.
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The 105hp 1.6 147 has the shortest final drive of the whole series, followed by the 120hp 1.6 then the 2.0TS with the selespeed having a longer 5th gear.

Don't worry about filling the revs completely out on the straights. As long as you pass max torque rpm, you are in the right gear. That should be 5000rpm.
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