UPDATE: 3800 sunfire swap

[IsaacCarlson]

http://ecomodder.com/forum/showthrea...wap-20678.html


the 4 banger in the sunfire was a piece of crap. All I was doing was fixing it and it never wanted to run. The 3800 gets good mileage and has plenty of power and I already have it.

FWD transmissions have chain/sprockets on the input side. They have to, to get the gears away from the crank axis. If you have a FWD, look into changing the chain and sprockets to a different ratio.

If I got 36 in the olds then it should be about the same in the sunfire. It weighs 800 lbs less and is more aerodynamic. Yeah, it'll be fast. That means I can get out of the way quicker. The old 4 banger got about 25 mpg with the gearing and high stall. The new converter has a 1420 stall and the gearing will be brought down and that should give me some decent mileage numbers to work with. I can always gear it down more later or put taller tires on it.

[Honda100]

+1 on the 2.2 being really crap. I had a buddy with a 2.2 Cavalier and whenever we'd go places, he ask if we could drive my car (Ford Taurus SHO) because it would in fact get 2-3 mpg better. Not to mention I had twice the power, more space, better ride, more accessories etc.

I'll be blunt, I loathe GM for the most part. But there are a few things I like about them, and the 3800 is definitely one of them. That and the LS motors. 3800 is a great engine, no doubt about that. I can't imagine what a Sunfire would be like with one of those,

[IsaacCarlson]

I think it will be a lot of fun. I have seen a few vids on youtube of cavaliers with 3800's and they are FAST. I don't really care how fast it is, just so long as it goes when I want it to. I am trying to make the 4t60 fit because it will save a lot of money. The only thing I need to do is check the fit of the axle shafts. I will do that in the morning. It will be a little while, but I will post a video when it is done.

[IsaacCarlson]

I was just looking over the gear combinations and I can get an overdrive chain/sprockets for the input side and drop the final drive from a 2.84 to a 2.53.

I am wondering what this would do to my power in high gear.

The gearing would be as follows:

55 mph 65 mph
current gearing 1428 1687
new gearing 1272 1503

I am thinking a gear swap would put me too low on the power curve. I would literally be idling down the road. I don't want it to downshift to go up every hill do I?

[IsaacCarlson]

Don't tell me I did it wrong, I know I didn't follow the directions, but the air is attached on the rear window, so i am going to use the window as a starting point.
I was messing around with the aero template and came up with this:
I will remove the spoiler and put a sharp edge around the back of the car for clean separation. What do you think?

[brucepick]

Originally Posted by IsaacCarlson

...
I am thinking a gear swap would put me too low on the power curve. I would literally be idling down the road. I don't want it to downshift to go up every hill do I?

Don't be afraid of a downshift. In this situation, I think it's a good thing.

At highway speeds, you pretty much want the engine running at low rpm so it's at maybe 60-70% load when cruising. Not super light throttle and 25% load, that would give you some engine braking constantly. The high loading puts you in the good part of the BSFC chart. Since it's running at kinda close to maximum output for its rpm, you will need more power if you want to maintain speed on a significant upgrade, or for acceleration. So you'll need a downshift for that.

If you don't need a downshift, you're running a lot more engine and/or a lot more rpms than you need. And your fuel economy will suffer.

Shucks, its an automatic. It will downshift for you. Now worries! With the tall gearing, the downshift won't bring the huge fuel economy penalty it would on a "normal" automatic.

[arcosine]

Swaping sprockets would be like driving into a 10 mph head wind with a 250 lb passenger.

[IsaacCarlson]

WOOOOOOOT!!! IT FITS!!!!

After sitting all winter in a snowbank, I pulled the 4t60 out of the olds just to make sure it was the wrong spline count on the shaft. The reason I thought the shafts were different is because 3 transmission shops said they wouldn't fit and so did the parts info at the auto stores. I thought I was screwed. NOT! I stuck the stub shaft from the 4t40 in there and it fits on both ends. All I have to do is get different seals. I did not have the time to check last year to see if it really would fit. Not only will the shafts fit in the transmission, but I can use the entire sub frame and weld/bolt it right to the bottom of the sunfire, saving LOADS of time, money, and parts.

This is going to be awesome! Maybe you can't tell, but I am stoked. This is going to be a LOT easier than I thought. If I would have known this in the first place, I would have pulled the entire unit out of the olds and stuck it in the sunfire and would have been driving it all winter. At least now the motor and transmission can get a good cleaning, paint, new seals/gaskets, and new fluid before going in.

The gearing will stay at 2.84 for the time being. I can always change it later.
I will use the dogbones from the caddy for upper torque mounts. That should keep things from moving around in there.

[IsaacCarlson]

If anyone wants to do a swap like this, the part numbers for the new axle seals are 710158 and 324204. These are National Seal numbers. It will be necessary to use the shaft sleeves from the sunfire. The shafts will pop right in.

[Smurf]

Just the other day, I was telling the girlfriend about people taking the 3.8L Supercharged out of my Regal GS and putting it in the 1996-98 Grand Ams. But in a SUNFIRE?! If you were a speed racer kind of guy, you'd be on to something pretty fun there.

I know yours isn't the Supercharged variety, but you could consider it later. I routinely got 33-35MPG in my Regal with five adults in the car. Minus their 800 pounds, and all the luxuries (power leather, dual climate, etc) I'd imagine a Sunfire would achieve great MPG with the 3800.

Looking forward to pic and video updates!