2wd to 4wd conversion

Craq · July 29, 2005

.......hi

I'm new here.

I'm looking at an '03 Silverado 2500HD with the Duramax and the Allison, and 50K. It's the crew cab/ long bed model. Right now it's marked at $23,495 and there isn't a THING wrong with it (clean Carfax record and everything). The only thing it lacks that I would love to have is 4wd. How difficult and expensive would it be to convert it to a 4wd with either an aftermarket system or with parts from a similar make/model? I understand it wouldn't be cheap, but say, compared to the option on a brand new model, is it expensive?

Hi.

Friz · July 29, 2005

I don't know about the new models, but the old 73-86 body style actually had a different floor pan on the 4x4s. It had a bigger hump to clear the transfer case. I'd look for a 4x4 if I were you.

pacodiablo · July 29, 2005

Converting late model IFS trucks to 4WD is generally extremely expensive. I'm not really familiar with the suspensions and drivetrains of full size GMs, but at the very least you will need new driveshafts, a transfer case, front differential and axles. I would be willing to bet money that you will end up having to replace your entire front suspension, adding at least one crossmember and possibly replacing the transmission. It really only makes sense if you want to make a SFA trail rig out of the truck. If you just want stock 4WD capability, you are much better off going with a factory 4WD.

Larry · July 30, 2005

Actually, it would not be all that difficult to add 4wd to an HD as they use the same frame, torsion bar suspension, ride height and everything as the 2wd. The 2wd and 4wd HD’s even have the same ride height. If you pop the center-bearing cap off of the front wheels behind the hub cap on a late model 2wd HD you will also notice the hubs have spines in them for 4wd usage. GM did a lot of parts consolidation between 2wd’s and 4wd’s on the GMT800 platform. Adding a transfercase would be as easy as removing the tailshaft housing and sliding on a transfercase on then locating a 4wd drive shaft at a salvage yard. If it were me, I would search high and low for a manual shift transfercase from an HD to save the cost and time to add all the harnesses and transfercase control module that will eventually cause problems anyway. PLUS, manual transfercases are better

In my opinion the 1999 and later trucks would be the easiest GM trucks ever built to convert to 2wd if you wanted to stick to the IFS stuff. However, as easy as it may be for some people the parts alone would add up pretty quickly. If you do not have a fair amount of wrenching experience you would be better off buying a 4wd to start with as the parts and labor to pay someone to convert it to 4wd would cost thousands.

99-2door · July 30, 2005

Actually, it would not be all that difficult to add 4wd to an HD as they use the same frame, torsion bar suspension, ride height and everything as the 2wd. The 2wd and 4wd HD’s even have the same ride height. If you pop the center-bearing cap off of the front wheels behind the hub cap on a late model 2wd HD you will also notice the hubs have spines in them for 4wd usage. GM did a lot of parts consolidation between 2wd’s and 4wd’s on the GMT800 platform. Adding a transfercase would be as easy as removing the tailshaft housing and sliding on a transfercase on then locating a 4wd drive shaft at a salvage yard. If it were me, I would search high and low for a manual shift transfercase from an HD to save the cost and time to add all the harnesses and transfercase control module that will eventually cause problems anyway. PLUS, manual transfercases are better

In my opinion the 1999 and later trucks would be the easiest GM trucks ever built to convert to 2wd if you wanted to stick to the IFS stuff. However, as easy as it may be for some people the parts alone would add up pretty quickly. If you do not have a fair amount of wrenching experience you would be better off buying a 4wd to start with as the parts and labor to pay someone to convert it to 4wd would cost thousands.

<{POST_SNAPBACK}>

You are mostly right.

The frame and suspension on the HDs is the same 2wd and 4x4.

however you can not remove the tailshaft and bolt on a transfer case. The output shaft is different between the two. You have to take apart the entire transmission to change the output shafts.

Larry · July 30, 2005

That maybe true on a 4L80E but not an Allison. That is what I was told when I went to Indianapolis for Allison 1000 Series training anyway. They said the tails were the same as far as spline count and mainshaft length. There are some other differences in the Allison 1000 as the units built in Indianapolis have the SAE round bell housing and the units built in Baltimore have the GM design bell housing. Some have a PTO gear in the trans and others do not.

Craq · July 30, 2005

wow, lots of good responses. Larry, you seem to know quite a bit about these. I would be using the truck for towing quite a bit, but I want to have offroading capabilities. I work at a small engine repair shop with 3 large bays and tons of air tools, wrenches, hydraulic hoists and jacks, etc. and a buddy of mine (Matt is his name) works with me there too who is a mechanical genius. He's actually done this conversion but on a much older model chevy truck. Between myself and Matt, we ought to be able to do nearly all---if not all---of the labor ourselves. The biggest issue at hand would be finding parts. Would all the necessary 1999 and up parts be compatible with this 2003?

.............are we looking at the $2-3K range if I do the labor myself?

99-2door · August 2, 2005

Ah... Wasn't aware the allisons were like that. Good info to have for the future.

Craq · August 2, 2005

Ah... Wasn't aware the allisons were like that. Good info to have for the future.

<{POST_SNAPBACK}>

Yes it is. I'm going to price all new parts as well as scavenge for used/reconditioned parts. Would I need to go to the dealership for parts or would I be able to get them at Napa/Autozone/O'Reilly's/etc.?

Larry · August 2, 2005

Crag,

Your not wanting to price all NEW parts as they will scare the heck out of you. You are better off combing the salvage yards for a wrecked 4x4 HD truck with an Allison and a manual shift transfercase. Preferrabley a roll over or a rear hit rig. Stay away from front end damage rigs. You will need the front axle (same ratio as the rear axle!), both axle half-shafts, fasteners, front and rear driveshaft (for the same wheelbase), manual transfercase linkages and interior bezel that goes around the shifter. Even purchasing used parts, I would expect that you will have at least 2K in just used parts to make this happen. Then there is always the extra 1K in stuff you didn’t foresee at the beginning of a project. Or at least, that is how my projects always turn out.

The reason I keep stating to go with a manual transfercase is because that will save you a bunch of wiring harness routing to the Transfercase Control Module and control head in the dash, PCM interface, etc. Plus, I am not a big supporter of any electronic shifted transfercase. They work great when they work. …..When they actually work. Notice all of the “Service transfercase” threads around the GM forums???

There is still one electronic gizmo to deal with even with a manual transfercase which is the front axle disconnect. That is still not a problem as you can use an aftermarket Posi-Lok kit that is intended to replace the electronic front axle disconnect with a manual system. Sort of like the ole manual locking hubs but the Posi-Lok is controlled via cable inside the cab. It sounds like your shop and experience could support a project like this.

Good luck and do a lot of research. I think it would be easy but who am I to say since I have never done it before to an HD truck. I am just familiar with the plateform and part usages. I converted my 78” K-10 from an automatic trans and fulltime 4x4 to a 4 speed manual and NP205 transfercase. That was a very easy project because I had a complete donor truck to swap parts with. The only thing was both had to work right when I was done so I could sell the donor that I bought with the intention of pirating parts off of and selling later as an automatic truck. Sold the donor to some sucker in Ohio while I still lived in MI.

MMM · August 3, 2005

Craq, you have a lot of good imformation here to go on. I have personally never done this conversion, but I have read several articles on this. Good reasons for wanting to do this would be if you have some sort of personal connection with this particular truck, and you would like to see it a 4x4. Or if you just want to do this for the challenge and experince of doing it yourself. But if you are doing this with the idea of saving money on a 4x4 truck, I think you will find out, in the long run, you will be time and money ahead by buying a 4x4 instead. You will definately have to find some type of donor truck from a salvage yard or something. Good luck. MMM

Craq · August 3, 2005

Craq, you have a lot of good imformation here to go on. I have personally never done this conversion, but I have read several articles on this. Good reasons for wanting to do this would be if you have some sort of personal connection with this particular truck, and you would like to see it a 4x4. Or if you just want to do this for the challenge and experince of doing it yourself. But if you are doing this with the idea of saving money on a 4x4 truck, I think you will find out, in the long run, you will be time and money ahead by buying a 4x4 instead. You will definately have to find some type of donor truck from a salvage yard or something. Good luck. MMM

<{POST_SNAPBACK}>

Well, there are several reasons why I want to do this. When I was shopping for trucks, I couldn't find a 4x4 in such good shape as this 2wd. I also want to do it for the reason that you stated---the challenge. I think it would be a blast to do, especially since everything should just bolt right up. (in the event they dont, however, I do happen to have a cutting torch ).

After all, if I was out to save money I would've bought a FORD anyway.

Craq · August 4, 2005

I found a wrecked '04 3/4HD 4x4 nearby........gonna see what all he's got. I know there's a front axle for $750. I need to see what else is left. Do salvage yards have fixed prices or is there room for negotiation? Also, what year models had the manual transfer case? (I know this one doesn't).