Can all metro transmission interchange? Are there different Gearings?


Idaho_Mechanic1984
10-09-2009, 08:05 AM
Does anyone know if the older Geo Metro Manual Transmissions will interchange into the newer cars?

For example, my local junkyard says they have a good 91 Geo Metro transmission for $300, and I have a 4dr 1996 Geo Metro with bad 2nd gear synchros.

Is this a straight swap? And if so does anyone know if the older trannys had a more fuel efficient gear setup or same, etc...?

Thanks for your help

- Dale in Southern Idaho

Woodie83
10-10-2009, 06:35 AM
There are three different gear ratios installed in Metros, four if you include Swifts (and Canadian Metros).

4.39 Convertibles and 95 - 00 three cylinders
4:10 Base and LSI Metros from 89 - 94
3.79 XFI and 95 - 01 four cylinders
3.52 89 - 94 four cylinders (Swift and Canada)

Lower numbers are more highway oriented and will get better mileage on the highway at the expense of acceleration. You should have a 3.79 in that car, the only gearbox with better mileage gears would be the rare 3.52.

Idaho_Mechanic1984
10-10-2009, 12:31 PM
Okay - great - Thanks for the info!

So do all the trannys interchange into these other years and models with no problem??

If so then I guess I will hold out until I can find a swift or canadian tranny to swap into my 96.

thanks again!

-Dale in Idaho

Woodie83
10-11-2009, 06:12 AM
Yes, they all fit with one caveat: There are two different mounting points for the shifter rod. On a four cylinder it mounts to the transmission case, on a three cylinder transmission, the hole is there, but it needs threads tapped into it to accept the bolt. On a three cylinder it mounts to an aluminum extension casting that sticks out of the case, many four cylinder transmissions don't have this extension, some have both.

In your case you're going into a four cylinder, the worst that will happen is to tap some threads. Plus, the ratios you're looking for only come in four cylinders, so you should be good.

Those 3.52 trannys are fairly rare, a standard replacement and some taller tires will yield you the exact same result and be easily reversible if you find you don't like the sluggish performance.

doug7x
10-16-2009, 05:43 PM
BEWARE OF THE DIFFERENCES IN TIRE SIZE....If you put that older tranny (came calibrated to 12"wheels) in your '95 (13" wheels), your speedo is going to read real slow. When I put the '96 swift tranny (13's) in my '91 XFI, I had to (well, I wanted to anyway) change up to 13" wheels. BTW...I've seen suggested several times on other posts that the 1.0 can't pull the higher gearing in the 4cyl tranny. My '91 pulls it just fine, & that's INCLUDING adding the larger tires, & a fairly tired engine (comp is 105-115-85 dry)...I get 80 mph easily...there IS more, but I normally run 55-60 mph for economy (currently getting 55-59 mpg). I'm going to do the head this winter...should improve a little more.

leonbentz
10-18-2009, 07:27 PM
What's the ratio in a '91 automatic?

Woodie83
10-19-2009, 05:14 AM
Simple answer? Your 91 auto has a 5.07 final drive ratio. It's not that simple at all, but that's a number you can compare.

I've seen it listed as both 3.87 and 4.10, hard to tell these stats sometimes as the brochures, owner's manuals, and factory service manuals often disagree. I know the standard five speed was 4.10 and one of the brochures said 3.87 manual and 4.10 auto, so I'm leaning toward those two numbers just being transposed. Let's assume the auto final drive was 3.87, but that is a misleading number and cannot be compared to the other numbers in the list above.

The manual transmission has five gears, two of which are overdrive. When you combine those two ratios together, it makes the final drive number 3.11, very tall indeed. In order to directly compare final drive ratios in a automatic to that list I posted above, you must multiply the true ratio by 1.31, in this case yielding a comparison number of 5.07 which doesn't even include the constant slip inherent to an automatic transmission. Now you see why an automatic loses so much gas mileage and engine life, it's spinning far far faster than a manual.

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