If I had a 3.9 and a 4.11 4eat which parts would I switch...

[ciper]

I have a turbo 3.9 4eat and an NA 4.11 as extras. Which parts would I need to switch in order to create a 4.11 turbo 4eat?

Reason, Id like to take my 3.9 turbo transmission and convert it over to 4.11 before sending it for a rebuild. Since the transmissions are both sitting I dont mind to tackle it myself if possible. If not Ill take both 3.9 and 4.11 transmisison to the rebuild place and let them do it. They probably know what they are doing but it would be nice to have additional information.

I sure wish I had an extra 4.44 auto (RS, Forrester etc..) to use. I already have a 4.44 ring and pinion for the rear differential sitting around. If I knew which parts to use I might be able to dig one up from the junk yards!

And yeah, I understand that I will be going slower for the same RPM if I do this.

[scottzg]

I already know you know this, but i would use the 3.9, personally. You will be flowing better at the low end to compensate for the taller gears, you will get better mpg, you can go faster in each gear, top speed will likely improve, less burnout risk (not so big a deal with awd), better suited to your meaty power curve build, freeway killer!

sorry i dont have the info, im a mt guy anyway.

[ciper]

I dont want better MPG or higher top speed though, I want to increase the mechanical advantage to the road. I already plan to run smaller than stock diameter tires to start. I also dont mind if my Speedo is 10mph off.

Having driven legacys with the same transmission and both gears I really like the numerically higher ratios.

[roodog]

slam in the 4.11 ratio, i can red line my rs in 5th, goes harder easier to drive in traffic, less gear changes to get moving, there again my bitch is 195kw at the wheels and working on getting more hp...

[ciper]

Can someone tell me if the Vss2 and speedo cable are driven independantly from the differential?

[Legacy777]

Pretty sure they're driven off the differential.

I thought I had a scan of a blow up diagram of it, but I can't find it now.

[vrg3]

That would make sense, because cars with 4.111 and 3.900 final drives don't have different gauge clusters, right?

[Legacy777]

technically they do....but it has nothing to do with the gauge cluster. The speedo gear in the differential has a different number of teeth on it to compensate for things. It gives you the number in the FSM.