6-Speed Swap

[twautomotive]

Has anyone thought about or has done a 1725 6-speed swap? The Chevy Colorado 6-speed looks like a good choice. I tried to upload an image but the site says, "The uploaded file was not an image as expected." Anyone know how to fix this? Thanks.

 

[husky drvr]

"The uploaded file was not an image as expected."

This one maybe?

I know nothing about this trans - more info, please.

Just as a wild guess, being a truck transmission, it's likely bigger than it seems and will have a wide spread of gear ratios.

If the info on RockAuto is correct, the stock disk is 10.12 inches on a dual mass flywheel of a bit over 11 inches diameter.

Just a thought,

 

[Asm109]

Sorry, looks like a poor choice to me. Mostly for the reasons mentioned by husky dvr. Not to mention the built in non removeable bell housing.
I'd be more inclined to figure out how to make a Miata 5 speed or early 6 speed work. At least you know they are geared for a sporty car not a truck. Later 6 speeds have a 1:1 6th gear and would be all kinds of wrong for an Alpine.

 

[belmateo]

The thing about Miata transmissions both 5 and 6 speed is they have an integrated bell housing.

 

[Asm109]

So does the colorado. Who knows maybe adapting a Miata fly wheel to the Alpine crank and a bell housing spacer adapter is a not that difficult. Use all Miata clutch and actuation components.
I don't know, I've never had an Alpine engine on the bench with this mission in mind.

Mind you, if someone has already figured out a T5 to alpine connection then in my mind there is no more need to wrestle with any other solutions. One more gear will not matter a hill of beans to a 75 hp engine in street use.

 

[husky drvr]

AI Overview
Learn more

The 2019 Chevrolet Colorado 6-speed manual transmission has the following gear ratios: 1st gear: 4.06, 2nd gear: 2.37, 3rd gear: 1.55, 4th gear: 1.16, 5th gear: 0.85, 6th gear: 0.67, and reverse: 3.20.


Here's a more detailed breakdown:

Gear	Ratio 1)
1st	4.06
2nd	2.37
3rd	1.55
4th	1.16
5th	0.85
6th	0.67
Reverse	3.20

 

[belmateo]

Miata 5 speed gear ratios

• 1st Gear: 3.136:1
• 2nd Gear: 1.888:1
• 3rd Gear: 1.330:1
• 4th Gear: 1.000:1
• 5th Gear: 0.797:1

And the six speed ratios
1st Gear: 3.709:1
2nd Gear: 2.190:1
3rd Gear: 1.536:1
4th Gear: 1.177:1
5th Gear: 0.897:1
6th Gear: 0.707:1
To be honest, if you are going to all that trouble to do this swap you might as well consider doing the entire engine trans swap. The benefits are many, EFI more power, better mielage, lower maintance, more reliable and quite affordable. You can ask @Toyanvil as I believe his is the cleanest swap I have seen.

 

[husky drvr]

I suspect the driving experience of the Miata five speed and an Alpine four speed with OD would be VERY similar on the road.

Series V Alpine from WSM 145

 

[Asm109]

I agree with Husky Dvr re: Driving experience between the two. The Colorado gears would be great if you plan to tow a boat with your alpine.

 

[twautomotive]

Found the problem with the Colorado trans photo. I changed it to a jpeg and it uploaded. 0.67 sixth gear sounds great for cruising.

 

[Asm109]

The RPM drop between 1 and two will horrific. You would not enjoy the experience.