3 speed manual with twin overdrive gears

[blueroo]

While taking a break from studying today (first two exams in college on Wednesday, nerves already fried) I had a thought. I had driven my car to school and back today and was just thinking how great the acceleration is with the 3 speed due to the ratio spacing and how economy roughly better in town since I'm 1:1 at 25 mph. However a 5 speed is great for highway economy since you're running about 1700RPM at 70mph vs 3200RPM at 70 with the 3 speed. Here's my thought though:

Take a t5, change the ratio clusters of 1st through 3rd gear so they're roughly equivalent to the 3 speed.

Remove the 4th and 5th gear clusters from the tranny and put 5th where 4th used to be.

Find a t56 and take 6th gear out of that and put it where 5th gear used to be in the t5.



I don't really know too much about transmissions. That's why this is just a thought. Is it feasible and am I correct in thinking you would get the better 3speed economy through town and better 5speed economy for the highway while retaining relatively good acceleration?

 

[wsa111]

If you want to use the 5 speed, use one from a 4 cylinder, especially since you have a 170 engine. You just can't start swapping gears.

The gears on the main shaft are mated to the countershaft, its a matched combination. The T-5 would be a great addition to your vehicle.

Will the cost justify the upgrade, heck no. $1000.00 will buy a lot of fuel. William

 

[blueroo]

Ok, thanks, Just thought I'd check.

 

[XFlow_Fairlane]

not to mention 4th isn't a physical gear....just a set of syncros between the input and main shaft.

the gears can be removed from the mainshaft but it is the cluster shaft (idler) that is fixed.

I say saw a t5 and change rear gears.

 

[Anonymous]

the od gear will reduce you rpm but not nearly as much as you stated. If you are currently running 3200 at 70 an OD will get you down around 2600-2800 rpm. in most trannies high gear is 1-1 and OD is reduced. High gear in a 3 speed and a 4 speed are usually the same, the extra gearing is usually in the bottom and middle area. A non OD 5 speed is still the same 1-1 ratio in 5th gear. Of course I'm sure there are some trannies out there that are completely different.