Tallest wheel setup for mpg.
 

I'm looking at doing the v8 swap into a 87 944 but I'm trying to figure if I can get a good cruising rpm. So what is the tallest rear tire I could run? I'm currently running 255/17/40, Could I move to 55's?

Remember that when you increase the diameter beyond stock (OEM) wheel/tires, you'll have innacurate speedo readings. Bigger tires, faster car for an indicated speedo reading.

you would be far better off swapping out the trans

Your 255/40-17's still match the overall diameter of the original tire - of which the system is balanced to. If you move to a different size tire like 255/55-17's the whole system will be off, including the speedometer rate, over-steer and others. The next question is will it fit under the wheel wells without rubbing - maybe no. Stick with known good sizes...

A turbo transaxle with the N/A 5th gear swap will give you a 2000 RPM @60 MPH.

Speedy:)

Is there any final gears longer than the 5th in a 944 n/a?

Yes ,the 0.68 5th from a '80-'82 audi 5000 diesel .If anyone can source these for a resonable price i'm also interested.
5th gear options, Audi?

You would be better off buying a Honda as a daily drive if you are worried about fuel bills....

255 i think are a bit skinny for a v8 powered 944 . As for dropping your rpm for highway cruising i would go for both soultions to get the best result,taller tyres and tall 5th (either 944na or audi) .And for the speedo side effect from tall tyres get a gps one from speedhut , ideola put one in his 924,should be just as easy to fit in a 944.

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