Arb Question: Can one "upgrade" a auto gearbox?

Kosmik

Kosmik

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Basically I'm wondering if it's possible to change a vehicles auto transmission to allow for more gears? Obviously this can't be done with the existing transmission as it would be mechanically infeasible but can a person switch out a 4 speed auto transmission for a higher one? or are there other restrictions.

Reason asking, I have a lovely old Toyota Avensis 2008 2L Auto. It only has 90k on the clock and the car is still in very good nick. However, the auto tran is a 4 speed which can be a bit inefficient fuel wise. The change between 3 and 4 is a bit rough and sometimes feels too early, would love it if there was a fifth, the engine can certainly handle it ( max rpm in 3rd is @ 160km/h ).

Thoughts, comments?
 
If a replacement transmission fits, yes it is possible, with a lot of work.
I have only done this with a manual transmission vehicle, converted it from 4 speed to 5 speed, which was not without its own issues.
 
Kosmik said:
Basically I'm wondering if it's possible to change a vehicles auto transmission to allow for more gears? Obviously this can't be done with the existing transmission as it would be mechanically infeasible but can a person switch out a 4 speed auto transmission for a higher one? or are there other restrictions.

Reason asking, I have a lovely old Toyota Avensis 2008 2L Auto. It only has 90k on the clock and the car is still in very good nick. However, the auto tran is a 4 speed which can be a bit inefficient fuel wise. The change between 3 and 4 is a bit rough and sometimes feels too early, would love it if there was a fifth, the engine can certainly handle it ( max rpm in 3rd is @ 160km/h ).

Thoughts, comments?
Click to expand...

Anything is possible, its whether the work is actually worth it.

It definitely won't be a simple swap out and replace job. There will be engineering work required to make the whole system 100% again.
 
ToxicBunny said:
Anything is possible, its whether the work is actually worth it.

It definitely won't be a simple swap out and replace job. There will be engineering work required to make the whole system 100% again.
Click to expand...

Hmmm not worth the effort then. Any savings in fuel would be eaten by the job. Also maybe I'm just being pedantic, only use 1 tank of fuel a month anyway :p
 
In the case of the manual transmission, I recall having to do the following.

* The clutch had to be changed, a bit of a mix and match because the splines on the 5 speed input shaft were different to the ones on the 4 speed box. The clutch was never really nice after that, prone to shudder because the pressure plate wasn't matched to the other bit. In the end we machined the flywheel to take a more standard clutch.

* The gear linkage was slightly different so I had to cut metal to make it work. I also had to change the car's mounting brackets, cut the old one out and weld a new one in salvaged from the same car the box came from, even though they were the same brand of vehicle.

* The speedometer never showed the correct speed, so I had to change the gear on the speedo pickup.

* The propshaft had to be shortened, a custom job, I had to have it done at a place I think it was Old Man Emu that helped me.
 
Should be able to slot in the 5 speed variant (U151E, was used in the 2.4L Avensis), they look similar. Then some ECU and cluster reprogramming and you're set. If the transmission is direct replacement I'd guess R50k?
Now think about how long would it take for the increased fuel efficiency to cover the costs and I'll bet you won't recover the costs earlier than 100,000km
 
Kosmik said:
Hmmm not worth the effort then. Any savings in fuel would be eaten by the job. Also maybe I'm just being pedantic, only use 1 tank of fuel a month anyway :p
Click to expand...

1 tank a month?

I hate you with a burning passion right now :p
 
I'll be honest, I've thought of so many travel saving ways ie: bike, e-bike, bicycle etc but nothing covers the cost of the initial outlay vs just using what I have. While it's not the most efficent, it's certainly the most cost effective. The other rider also is that I need a vehicle for work and have to maintain a certain level of vehicle.
 
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