UPDATE: 3800 sunfire swap

[IsaacCarlson]

The axle parts won't swap. They have two different carriers.

I will have to use the 4t40 and alter the B solenoid wiring so it does the opposite of what the PCM tells it to.

[rmay635703]

Originally Posted by IsaacCarlson

The axle parts won't swap. They have two different carriers.

I will have to use the 4t40 and alter the B solenoid wiring so it does the opposite of what the PCM tells it to.

If you have the skills and the patience, get it working right (it looks like you did)

and you can always go back in there later and drop in a final gear swap.

Although trust me, once its done and working its hard to go back in.

The fuel savings from going from a stump puller to an airplane can be rather large.

The FE difference on my buick at basically every speed comparing 3 to 4 was massive, at higher speeds I lost about 40%

Spinning that big brick comes at a price, hopefully you mainly want this car as a town hopper and it won't be too bad for that.

If you do venture on the highway get a fuel economy guage of some sort, I would guess 40-50mph will be your sweet spot.

This may be one of those oddball situations where big tires would save fuel, if you want to scrap out the wheelwells and find some light 19" or 20" wheels

Sadly 20" wheels cost more than the final though

Good Luck and keep us posted.

[IsaacCarlson]

I am not really sure what I can do with the final drive right now. It seems that is the lowest I can go. I will call a tranny shop and find out for sure. It sure would be fast. I could always sell it for $$$$ and get a fuel sipper.

[IsaacCarlson]

I have a guy looking into the final drive on the 4t40. He thinks he can get it down to 2.87ish, which would be perfect. I will be installing a few new components in the tranny to make it hold up to the power.

He also told me that I can use a 5 pin bosch NC relay to drive the B solenoid.

YAY!!!

[rmay635703]

Originally Posted by IsaacCarlson

He thinks he can get it down to 2.87ish, which would be perfect.

He also told me that I can use a 5 pin bosch NC relay to drive the B solenoid.

YAY!!!

Sounds good, with that big of a motor the higher you get geared (numerically lower) the better, assuming you do not loose lockup, so anything in the 2.5-2.8 range is probably going to work out well.

Good Luck
Ryan

[IsaacCarlson]

I have done a lot of figuring over the winter and started working on the car again today. Not much, just getting my bearings again....LOL

I am looking for any ideas on the gearing. I have to get a new chain and sprockets to handle the extra power, so the mileage won't be too bad to start with.

Current gearing: 3.91
New chain/sprockets: 3.05 should be a huge improvement
New diff: 2.54 $1000+

Would it even be worth it to mess with the diff?

[pete c]

at a thousand bucks? No.

[Miller88]

Why such a big engine in a sunfire? Isn't that a cavalier?

[brucepick]

Chain and sprockets?
For a moment I thought maybe it was a motorcycle, or a project car with a motorcycle drivetrain.

Your car's page:
Details: 3800 Sunfire - 2002 Pontiac Sunfire Fuel Economy - EcoModder.com

Anyway, I don't see how swapping in a 3800 cc engine to replace a 2200 cc engine will improve fuel economy. Unless its actually a performance project and you just want to make some effort to keep it from becoming a total fuel hog. In which case you may be on to something.

But what are the chain and sprockets?? I don't think you'd be changing the gear ratios of a timing chain. It must be something else.

[MetroMPG]

Isn't there a thread about your project already?

It makes more sense to post your updates there than to start a new thread. Post the link and I'll move these posts over, if you like.