UPDATE: 3800 sunfire swap

[IsaacCarlson]

I managed to get the 3800 out of the Oldsmobile today. That baby is heavy! I bet it weighs almost as much as the 2.2 AND tranny put together. I will be putting new gaskets in it and fixing anything that needs to be fixed and then bolting it to the 4t40. The 4t40 is a lot smaller than the 4t60, but is supposed to be pretty tough. I have seen really tuned up motors bolted to the 4t40, so it should be good to go.

I am pretty sure both cars used the same converter.

I also removed the exhaust from the olds. It was fairly easy and I am glad it is done. It will get cut and welded to fit the sunfire, and the sunfire exhaust will come out with a sawzall.

I have been messing with the idea of putting the 2.2 in my john deere M since it only has 20 HP and could use some GIDDY-UP!!! Bolting on another 100 horses should be fun right?

Pics will be up tomorrow, I'm tired.

[MetroMPG]

Isaac: I combined your update into this existing thread about your project.

(No need to start a new thread when you update, or the project progress will be scattered throughout the forum.)

Best to just keep updating here.

[IsaacCarlson]

OK. I did the compression check. I almost dirtied my pants when the cylinder hit the first compression stroke....200 lbs of compression!!! I was not expecting much over half of this and was unable to hold the gauge in the hole and it came out, propelled by 200 pounds of air pressure, and I landed on my hind parts. The battery I had was losing charge and the numbers dropped to 180 across the board on the second try.

I don't have to pull the heads! YAY!!!! This makes me feel so much better. I was worried I would have to stick a ton of money into gaskets. I might be able to get away with just replacing the valve cover gaskets.

I am not sure how much more I will get done today. My brother called and said he bent one of the i-beams on his truck.....turns out he got stuck in dad's field and instead of asking dad for some help, he got the neighbor to help. They used a chain and got some good running starts He is coming over to have me look at it and maybe put a new front end in his truck....

[IsaacCarlson]

The final drive on the 4t60 was 2.84.
I just found out the final drive on the 4t40 is 3.91.
You can see where this leaves me.

Instead of turning 1500 rpm at 55 I will be turning 2000.
and while I was doing 1750 at 65, I will be doing 2500.

What is this going to do to my mileage?. Granted, I could climb a mountain in 4th gear...but still. OH, and the transmission shifts in the opposite order!!(4-3-2-1) what gives?

I might have to see if the 4t60 will fit.

[MetroMPG]

I suspect it'll pretty much negate the purpose of doing the swap (from the fuel economy perspective). Have you or anyone ever done a gear vs. fuel consumption chart for that drivetrain? eg:



( from: Showdown: testing RPM vs. MPG at a fixed speed - MetroMPG.com )

If anything, you should be gearing the V6 drivetrain to spin at even lower RPM than it did in the Olds, since you'll be pulling less car around behind it. That would be the only reason I would attempt this swap, personally!

[rmay635703]

Originally Posted by MetroMPG

I suspect it'll pretty much negate the purpose of doing the swap (from the fuel economy perspective). Have you or anyone ever done a gear vs. fuel consumption chart for that drivetrain? eg:

If anything, you should be gearing the V6 drivetrain to spin at even lower RPM than it did in the Olds, since you'll be pulling less car around behind it. That would be the only reason I would attempt this swap, personally!

I didn't have his exact year but on the buick 3800 that would be like driving in 3rd versus 4th and fuel consumption skyrockets above 1500 RPMs from about 40mpg down to about 25mpg 1500-2000rpm

I believe he might be best going to a local transmission place that is willing to work with yah so to say and get a final drive swap done.

I would think a 2.73 would work best, maybe even a 2.5

Cheers
Ryan

[IsaacCarlson]

I talked to a guy today who makes limited slip diffs for fwd. He said he can send me a set of overdrive sprockets that would give me a final drive of 2.53 for $200.

I also asked about his limited slip diff, and he said that would be $600. It would be nice to have a limited slip diff in the snow and off road.

[MetroMPG]

2.53... going to do it?

[rmay635703]

Originally Posted by IsaacCarlson

I talked to a guy today who makes limited slip diffs for fwd. He said he can send me a set of overdrive sprockets that would give me a final drive of 2.53 for $200.

I also asked about his limited slip diff, and he said that would be $600. It would be nice to have a limited slip diff in the snow and off road.

$200 is definatley worth conservatively 5-8mpg better on the road I would say.

The trouble is this will sno ball, because you now need a shift kit (or need to rig the transmission yourself) to ensure it locks up at lower RPMs.
You also will get a chance to do a lite rehaul of your transaxle which may be worthwhile. (seals, boots, bushings, outer bearings)

This will definately be an interesting conversion.

Good Luck

[IsaacCarlson]

I don't know if I am going to do it or not right now.

The rpm difference, I can live with if I have to. I just need a car.
I have been looking over the schematics for these transmissions and noticed that the shift pattern on the 4t40 is only half backwards.

The A solenoid is used the same on both. It is the B solenoid that is switched backwards. All I have to do is put a PNP transistor in the solenoid wire and it will do the exact opposite.

I have also thought about using the 4t60 if I can splice the CV shafts. I am going to take the inboard end from the 4t60 shaft and put it on the 4t40 shaft and see if it fits. If it does then I will use the 4t60.