Gas to diesel swap

[MZmiejko]

Hello all. This is my first post after many magazine issues. I have a 1989 W-350 4X4 with 360 gas motor. I can buy an early 1991 2wheel drive 2500 non inter-cooled truck with 150,000 miles for $1,000. Does anyone know if the 727 trans. bell housing and torq converter in the 4X4 will match to the cummins? Also if I buy a used inter-cooler and tubes from a factory inter-cooled truck, can I install them on the 1991 motor? Is there any other parts I would have to get along with buying the complete running truck? Thank you for the help.

 

[RWherley]

Im not sure about the trans but as far as the intercooler goes, the engine is not the problem all you need to change on it is the intake horn, the problem is the your 89 radiator support and grill are different you ether need to find a rad support from an intercooled truck or do some cutting a welding on yours for the intercooler to mount in it, if you are going take the time to custom fit a intercooler to your rad. support and plan to turn your engine up at all do your self a favor and get the intercooler and radiator from a second gen truck they are much bigger then the factory first gen ones. You may also need to cut another set of engine mount holes into your crossmember that holds your engine up.

 

[MZmiejko]

If I keep it all stock and just want to plow snow,haul some things local,should I even bother to inter-cool it?

 

[RWherley]

There are other people doing just that, with out intercoolers.

 

[MZmiejko]

Thanks for your help. Now I just have to find out if the 1989 trans. will work.

 

[cerberusiam]

A gas engine 727 transmission will not bolt to a Cummins engine adapter. The Cummins specific 727 was a rare one-off production piece that is extremely hard to find.

 

[RWherley]

double check but if the diesel has an auto trans you should be able to take the tail shaft off your gas trans and put it on the diesel trans to use your transfer case.

 

[cerberusiam]

double check but if the diesel has an auto trans you should be able to take the tail shaft off your gas trans and put it on the diesel trans to use your transfer case.

Can't just change the tail shaft, have to tear the trans down and change the output shaft also.

The second problem will manifest as the gearing on the gasser is probably not going to be adequate for the diesel and a 3 speed transmission.

 

[AClayton]

Confirm the gear ratio in your truck. If the gasser had 4. 10's, then after you swap in a Cummins with the 727 your top spd will be about 55mph

 

[RSchwarzli]

A few thoughts:

1 - The gearing in the diesel transmission is very different as a gasser can see revs at 5000 rpm, and the diesels were tapped out at 2600 ish. So to be able to do highway speed... .

2 - The transmission will not bolt up

3 - The TQ converter is different too I believe

4 - IC pipes from a IC truck will not work with the non diesel rad core support (or the rad core support in the NON IC CPL 0804 Cummins trucks). It can be made to work with some fabrication but it will not be bolt in.

5 - If you swap engines, you will also need to swap rads.

6 - Suspension wise your front springs I believe are a bit weaker than the cummins ones. Sag may be an issue.

7 - Really, if the truck is complete, you can almost swap everything cab forward and you should be good. I also want to say there was something different with the brakes as well gasser to diesel but I can't fully recall this.

 

[MZmiejko]

I know the truck will be slow with out the over drive. But it only has 3. 54 gears, so it wont be too bad as I just want it for local use,no hi way. I have 2 other Cummins for that. This is just a cheap work truck. I got the w350 with 27,000 miles for $300. 00 with a bad fuel pump and a good body which is unusual for Pa. I spoke to a trans shop and and they will change the tail shaft for a small amount. I will forget the intercooler. I am buying the whole 2 wheel drive truck with a new rad. so i am good there. I am a mechanic so the rest I should be fine with. I think you guys answered everything I did not know. I would like to thank all of you for your replies and the information. Thanks Mark.

 

[RSchwarzli]

Good luck Mark!

 

[MZmiejko]

Thank you.