4wd to 2wd conversion

[Ricko1966]

I have a 1975 3/4 ton 4wd gmc. I do not need 4wd do do have to pull heavy trailers so the 3/4 ton suspension is a good thing, The truck has lock outs on front so my thinking is put the lockouts in freewheel put in a turbo 350 from a car score a drive shaft from a 700r4 2wd truck and get on down the road.I am concerned about pinion angle 2wd vs. 4 wd anyone know if they are the same? What else am I not thinking of? Thanks

I was going to do it to get better milage if I can just spin the lockouts pull the front drive shaft run in 2 hi and get similiar milage thats what I'll do I thought those old cast iron transfer cases robbed horse power and were gear reduction.

Okay swapping to 2wd sounds maybe pointless I was going to pull the 4x transmission anyway because it has a pretty big torque conv. seal leak. and a bent flex plate. The truck has no A/C pwr steering is only acc. no exhaust yet I'm thinking it would probably be easier to pull the engine than the trans and transfer case. Anyone?

 

[HotRodPC]

Blah blah blah, it's a bunch of ******** and a lot of time. I'd like to have another 4x4 frame, sooooooo why don't you drag that thing down here to OK and swap me for this 85 C20 frame??? Auto Trans crossmember and driveshaft included.

 

[Honky Kong jr]

Blah blah blah, it's a bunch of ******** and a lot of time. I'd like to have another 4x4 frame, sooooooo why don't you drag that thing down here to OK and swap me for this 85 C20 frame??? Auto Trans crossmember and driveshaft included.

Rehr ft ft.......lol

 

[bucket]

I have a 1975 3/4 ton 4wd gmc. I do not need 4wd do do have to pull heavy trailers so the 3/4 ton suspension is a good thing, The truck has lock outs on front so my thinking is put the lockouts in freewheel put in a turbo 350 from a car score a drive shaft from a 700r4 2wd truck and get on down the road.I am concerned about pinion angle 2wd vs. 4 wd anyone know if they are the same? What else am I not thinking of? Thanks

What would be the benefit? If you don't need 4x4, it would be much simpler to just not use it. NP203? If it's converted to part-time, just run it in 2HI. If it's not converted, just run the hubs unlocked, pull the d-shaft, and run it in HI LOC.

 

[Honky Kong jr]

Sell it and buy a 2wd 3/4 ton. That be the least work and ride better too.

 

[Ricko1966]

If I can get similar milage in 2hi I'm just going to run in 2hi I thought there was a big difference in mpg between 2 and 4 wd never owned 4wd,haven;t even driven this one yet, It s under construction. I live in linn county ks. don't even live in a town the grocery store is 50 miles round trip just wanted to make the truck affordable to use.And I have a turbo 350 out of a chevelle in the barn and a driveshaft out of 700r4 equipped 86 suburban I junked, but if there is no big advantage to going 2wd I will keep it 4wd I can use it occasionally, Thanks for your input bucket.

 

[1987 GMC Jimmy]

I would say the difference in economy is negligible. There are plenty of other ways to ensure you're getting the best economy, though. If you're not running a lift and massive wheels, you maintain good tire pressure, your brakes are in good shape, your ignition's tuned up, you have a good air filter, you have no vacuum leaks, your carburetor's tuned and in good shape, and your exhaust system is not the choked up factory setup with those manifolds, you've likely matched the gain of what the intricacies of a conversion would have netted you. You could get a little more by changing the gearing and doing a 700R4, maybe some other things. However, those are more involved upgrades. I'm not a fan of full time four wheel drive, myself, but for me, part time is a great thing to have in my back pocket should I ever need it.

 

[HotRodPC]

What would be the benefit? If you don't need 4x4, it would be much simpler to just not use it. NP203? If it's converted to part-time, just run it in 2HI. If it's not converted, just run the hubs unlocked, pull the d-shaft, and run it in HI LOC.

Not a bad suggestion, but I kinda get it why a guy would want to go 2wd if he didn't need the 4x4. Fact is, straight axle certainly isn't as comfy as IFS on coil springs. And the added weight of the Tcase and front axle not being necessary and having to push that dead axle hurts the mpg and the giddy up too. Front Brake bearing and maintenance is much easier and cheaper on a 2wd IFS too. JMO, besides don't be talking him out of it. I need that 4 wo wo frame and front 8 lug axle. I'm trying to work on a swap here buddy.

 

[Ricko1966]

Thank you I just didn't know, I have land and board horses, I don't trust 700r4s pulling heavy trailers,but now that I know there isn't a huge difference in milage between 2x and 4x I will be glad to have the 4wd when the pasture is soupy. Thanks for your advice. I really didn't think a 2wd swap would be a big deal but now it sounds unneccesary. thanks again.

 

[HotRodPC]

Yep, I'd have to say the only difference in MPG is 2mpg. In my C20 with a 454 on the hwy with a light foot I was getting 13.2mpg. Towing that went in the ******* to about 8.5 to 9. In my K1500 with a 350, the very best I could ever get was 11 and that was driving very slow at 60-65mph. At 70-75 it would drop to about 9. Now around town, both seemed to be in the 8 - 8.5mpg so really no difference around town. Gear ratios probably made a difference. The 350 in the K1500 was peppy with a Th350. The 454 C20 was running 3.21 and 3.42's after the swap and a Turbo 400 and IMO was a sled.