3.7 / 3.54 rear diff

[Filip]

Is it straight swap, or i have to change rear axles as well ? Just out of curiosity, what would happen, if transmission and rear differntial would have different final drive ratios ?

With regards,
Filip

[Trevor]

Originally Posted by Filip

Is it straight swap, or i have to change rear axles as well ? Just out of curiosity, what would happen, if transmission and rear differntial would have different final drive ratios ?

With regards,
Filip

Both ratios must match, be the same, otherwise the transmission will become damaged. Front and rear would be fighting each other through the transmission.

[Filip]

Good explaining Trevor. What about rear axles, are they same across markets, so i can just swap rear diff for 3.54 one, without buying 3.54 axles too ?

Filip

[oab_au]

The rear has to be the same ratio as the front diff, auto or manual.

Depending on which box you are putting in the car. If you use a box with a different front ratio, you will have to get the rear diff from the same car as the box so that you have the same ratios.

To use the 4.44, 4.1, or the 3.5, ratio you will have to swap the ring and pinion gears, from the low ratio diff and fit them into the SVX housing, using the SVX Limited slip centre, so that the SVX axles will fit the diff, they won’t fit the low ratio diff from another model.

If you use a 6 speed that box has a front ratio 3.7 the same as the rear diff in your VTD and you can still use the R160, changing to the R180 is not necessary.

[Filip]

Originally Posted by oab_au

The rear has to be the same ratio as the front diff, auto or manual.

Depending on which box you are putting in the car. If you use a box with a different front ratio, you will have to get the rear diff from the same car as the box so that you have the same ratios.

To use the 4.44, 4.1, or the 3.5, ratio you will have to swap the ring and pinion gears, from the low ratio diff and fit them into the SVX housing, using the SVX Limited slip centre, so that the SVX axles will fit the diff, they won’t fit the low ratio diff from another model.

If you use a 6 speed that box has a front ratio 3.7 the same as the rear diff in your VTD and you can still use the R160, changing to the R180 is not necessary.

Harvey,

that would be great news, but are you sure ? Because from reading other topics here, i got feeling that 6 speeds are 3.9 and thus can be used only with US model 3.54 due to centre diff conversion.

Can you please confirm me, that i really can use 6 speed, either from 06,07 or 08+ Imprezza STI models ?

With regards,
Filip

[Trevor]

Originally Posted by Filip

Good explaining Trevor. What about rear axles, are they same across markets, so i can just swap rear diff for 3.54 one, without buying 3.54 axles too ?

Filip

Kia ora Filip,

Your questions appear to indicate that you may have decided to replace your transmission, rather than at first find out if your problem can be fixed without great expense.

The cost involved in replacing the transmission, when considered against the value of the car, requires careful thought. As also does the fact that the car will no longer be an original collectable example and therefore will lose market value.

Regards, Trevor.

[Filip]

Originally Posted by Trevor

Kia ora Filip,

Your questions appear to indicate that you may have decided to replace your transmission, rather than at first find out if your problem can be fixed without great expense.

The cost involved in replacing the transmission, when considered against the value of the car, requires careful thought. As also does the fact that the car will no longer be an original collectable example and therefore will lose market value.

Regards, Trevor.

Ahoj Trevore ,

Those are all important things to consider, indeed. I was thinking about them intensively past two months.

I could write whole letter about my thoughts, but i won't. I only ask you two questions, whose answers would help me:

...1) How many actions would remain, if solenoid C were to be OK, before you would recommend me an "expensive" solution?

...2) I suppose you have the same gearbox as me, so i would be curious, how are your experiences with it? Could you describe it as reliable?

By reliable, I also mean, you don't have that unpleasant inner feeling, that the tranny will let you down in most inconvenient times and that you don't worry about depressing the gas pedal strongly from time to time.

But please, don't imagine me as a guy, who is redlining a cold car, etc. I am trying to do my best to be gentle. But even gentlemen wanna have some fun sometimes!

Filip

[Trevor]

Hoooooray Filip,

(1) Please refer my posts within your previous lengthy thread “3rd and 4th gear not engaging + weird smell”.

(2) I had no qualms in respect of my SVX as I had fitted a pressure gauge which constantly displayed the transmission line pressure so tat it was clearly visible in front of the steering wheel.

But please, don't imagine me as a guy, who is redlining a cold car, etc. I am trying to do my best to be gentle. But even gentleman wanna have some fun sometimes!

My sport has been motor racing and on two occasions I came very close to death! As long as you always drive the car correctly rather than specifically gently, you can have lots of fun.

In all of this, fitting a manual transmission in order to have fun, involves an entirely different set of circumstances and therefore it could be worthwhile.

Cheers, Trevor.