So, a freak transmission failure forced me to replace the tranny in my SL2. Apparently the gears were feeling claustrophobic so it decided to blow a 3” hole in itself with the diff pin.
Since I had to replace it anyway I decided to swap it out with a trans from a single cam car. For those that don’t know Saturns, the single cams had wider spacing of ratios and a much taller overdrive (not to mention an OD 4th as well). I had been thinking about doing this swap for some time in the hopes of lowering my cruise rpm (I do a lot of highway driving) and, hopefully, gaining some mpg’s; this failure just forced the issue.
The swap itself is VERY straightforward; it literally bolted right up, all the sensors hooked strait up and it requires no modification of any sort.
Saturn seems to be one of the precious few carmakers in the last 30 years that made an honest effort in trying to make their vehicles “mechanic friendly”. A complete transmission swap can be done in 4-6hours by a single, reasonably competent, shade-tree mechanic. I’m confident that if I had to do it again I could start first thing in the morning and be done by lunchtime; it really is a piece of cake.
Anyway, my impressions thus far:
-Why didn’t Saturn offer this combo from the start? The twin cam engine and that single cam manual play very nicely together. There is still plenty of passing power available (although passing in 5th is an exercise in patience-dropping to 4th solves that
) and the RPM at a 60mph cruising speed have dropped from just over 2500rpm to just barely 2100. The car positively “glides” along and only a steep hill would require a downshift at anything over 45/50mph.
-The ratios feel generally well matched to the power characteristic of the twin cam. The close ratios of the old tranny felt “sportier” but the tall gearing of the new trans doesn’t create any problems in terms of “not having the right gear”. There seems to be a break point around 30-35mph where 5th is just almost too tall but even in 4th (which is also an overdriven ratio) the rpms are barely 1500-1600 at those speeds; in 5th it's more like 1000-1100.
-MPG’s do indeed seem to be up. My winter-time mileage has been hovering right at 37mpg (+/- .5mpg-I tend to be very consistent). My first tank with the new trans netted me 40.2mpg (equal to my best summertime numbers). It’s still a little early to call a mpg gain but it would appear as though I’ve easily picked up a couple.
Overall, I’m happy with the swap. If this one blew up tomorrow there would be another single cam tranny going in. For my highway driving the relaxed feel of lower rpm’s just makes for a nice ride and it would appear as though there is a mpg bonus to it as well.