A few questions about a 4x4 conversion

[zeusflash]

I currently own a 69 3/4 ton 2 wheel drive pickup and want to do a chassis swap to four wheel drive. I have been searching for a 71 or 72 3/4 ton 4x4 to donate the chassis. So far I have not had much luck. Today I went to look at a 72 GMC 3/4 ton 4x4. It is on the Spokane area Craigslist offered for $1350. The GMC has an automatic trans,power steering,power brakes,some A/C and rust,the bad has been swapped and is very solid though. The big dilemma is the cab. It is an A/C cab and also has running lights so I am considering doing the rust repair and using the cab. My understanding is that Chevy and GMC cabs are the same(and I need the high hump floor anyway). Is this correct? The other question is about the rear end. My 69 has a HO52 with a locker which I would like to use. The GMC has a Dana 60. Will a leaf spring HO52(2 or 4wd) bolt to the springs in place of the Dana 60. I suppose the Dana could be limited slip but I don't know since the SPID tag was gone. My 69 also has a 427 and a Turbo 400 in it so a motor and trans upgrade may also happen. I think that I could get the GMC for $750-$1000. Any answers,thoughts ,opinions would be greatly appreciated, especially from you guys who have done this type of swap.

[CG]

Cabs are basically the same. On a 4x4 the front and rear differentials have to be the same or super close to the same gear ratio's. Im sure someone will chime in with the exact ratio requirements.

[haysonj]

Originally Posted by CG

Cabs are basically the same. On a 4x4 the front and rear differentials have to be the same or super close to the same gear ratio's. Im sure someone will chime in with the exact ratio requirements.

mine had 4.09 in front and 4.10 in back I changed the back to a 14 bolt corp with 4.09 gears.

[old Chevy guy]

The rear should bolt in no prob but the ratio has to be the same or the wheels will turn at diffrent speeds in 4 wheel drive and that adds up to broken parts.

[justcuz]

The Dana 44 front and the Dana 60 rear should have the same ratios. For some reason GMC used Dana 60's and Chevy used the Eaton(HO52). I think the Eaton is a stronger rear axle just a little harder to get parts for especially brake parts. That can be solved by using 14 bolt brackets and converting to rear discs on the HO52. If the ratio is close, I would keep the HO52.
You could run a 4.11 rear axle with a 4.09 front and not have any issues if the driving surface allowed for some slippage (you shouldn't be in 4wd if it doesn't)!

[Jtrux]

There can be a slight difference front to rear, very slight. Actually some off road guys prefer the front to be higher than the rear so that in sticky situtions the front spins a little faster than the rear. so a 4.09 front and 4.10 rear would be exceptable. If I read correctly you don't want to go much more than that cuz you start breakin stuff (xfer cases, etc.)

[Critter]

Originally Posted by Jtrux

There can be a slight difference front to rear, very slight. Actually some off road guys prefer the front to be higher than the rear so that in sticky situtions the front spins a little faster than the rear. so a 4.09 front and 4.10 rear would be exceptable. If I read correctly you don't want to go much more than that cuz you start breakin stuff (xfer cases, etc.)

I have never liked when people do this. It just doesn't seem like a good practice, too dangerous in my opinion. Besides zeus is in Idaho not Forida...I have a feeling he will be in the rocks more than the mud. Just my $0.02

[Jtrux]

Originally Posted by Critter

I have never liked when people do this. It just doesn't seem like a good practice, too dangerous in my opinion. Besides zeus is in Idaho not Forida...I have a feeling he will be in the rocks more than the mud. Just my $0.02

True, but I was just saying, there can a be a slight difference but you're right, not good practice. If you want a difference in tire speed, just put smaller tires on the front, works great for mud racers anyways.

[zeusflash]

Thanks for all the input guys! My HO52 is a 4.10. I am not sure of the GMC's ratio,but a 3/4 ton auto 4x4 would most likely also be a 4.10/4.09. I also believe that the cabs are the same and it would be nice to add the A/C and cab lights. The other thing that bothered me a little is that the factory big hub front lock outs are gone and we all know how spendy those can be!!!! Still if I can get the truck for $750-$1000 it may be worth it. One more minor issue is that the brakes on the GMC do not work so no test drive to check for other issues. The truck has been sitting for about three years. Great bargaining point though. Motor runs and sounds good,trans is supposedly rebuilt also. Only a few miles from the house so if I could get some brakes I could drive it home. I look forward to hearing from more of you. I will most likely call the guy this afternoon with a decision. I will let you know what happens.

[FormerMember]

...

[Critter]

I know it's done quite a bit...just doesn't seem right, though. I guess it's something I need to get over.

[Sinisterspeed]

If your looking into doing the 4x4 conversion. Choosing the gear ratio's is much further down your list then you might think. These are easy and fairly cheap to take care of no matter what the ratio's currently are. You could put the AC dash in your non ac cab however the ac box wont fit the firewall without modification. Then of course there are a ton of other more expensive parts that are needed to make all that work.

IMHO it all depends on the condition of your truck. If yours is in good shape just use the 4x4 chassis and start from there. You can convert the 2wd chassis just takes alittle more time and you still need some parts from the 4x4 anyway.

There is also a after market kit you can use to just change your 2wd to 4wd but a donor truck is always a good source for the parts you need.

1. tcase (150-300)
2. short shaft married transmission (150-300 used 450-1200 rebuilt)
3. correct adapter between them (75-300 depending on which one you will need TH400/205 is the hardest to find)
4. cross member that holds them to the frame (home made or OEM donor)
5. front leaf perches (OEM or Aftermarket)
6. Front Axle (don't bother with the trouble unless it is at least a disk brake, open knuckle with locking hubs usually can be had for 150 or less)
7. 4wd steering box (you can use 2wd box if you do crossover steering 75-150)
8. drag link (50)
9. front springs (50 used -250 new)
10. raised center hump (this does not HAVE to be done. You just can't reach the top bolts without a body lift to install the tcase separately)
11. Front and Rear Drive lines (I usually budget 5-600 for this if you have to have them both made. I usually just mix and match to make a front one since a non balanced front shaft wont hurt anything since you only use it at low speeds and its so short)
12. If you will be running a lift kit when it becomes a 4x4 make sure you measure the rear springs on the frame you are using because lift kits usually only come with 52" springs where longhorn's as well as a couple other 2wd trucks have 56" springs therefore you have to relocate both the front and rear spring mounts to make this work as well. (I might be mixed up on the which has the 52 and 56 but I think I remember it like that) I had to move mine closer together to be able to buy the springs that would fit)


Issues to think about when doing this as well to prevent future problems are:

if your in it this far reinforce your frame at the PS box or add cross member in front of it to prevent breakage from the larger tires twisting on the frame

Speedo most likely will need attention at the trans to make it right with your tire size and gear ratio that you have chosen

rear axle should be from the same truck as the front if possible to prevent having to change the ratio from one or the other right away.

obviously if you have a half ton 2wd you will most likely not have rear leaf springs either. Thus another reason to use a 4x4 frame or a 3/4-1 ton 2wd frame then you can use the factory rear spring mounts.

you will have to remove the carrier bearing cross member from a 2wd frame.

you need an additional side transfer case mounting bracket. You can mount it up without one but if you run without it very long you will damage the trans adapter and those are 300 bucks by them selves.

I am sure I am forgetting something but those are the issues I could think of while I have been doing mine. The prices as well are prices that I had found while doing this in the Pacific NW with many parts available.

[padresag]

there is a reason for that minor difference 4.09frt and 4.10rear ratio and I don't remember what it is
ron

[Sinisterspeed]

Originally Posted by padresag

there is a reason for that minor difference 4.09frt and 4.10rear ratio and I don't remember what it is
ron

The answer to this if I remember correctly is steering. It is supposed to make it steer better. If your front ratio was lower then your rear it would be pushing the fronts around thus making it handle terrible. With it .01 taller in the front it actually pulls on the rest of the truck thus making it turn better in severe off road traction issues. In other words its supposed to make it work better as a 4wd this is the reason that older trucks say a max of 25 or 35 mph while in 4wd this keeps the front and rear turning pretty close to the same but the newer stuff has the same ration thats to allow you to run it in 4wd while on gravel roads or icy conditions as well as allow for shift on the fly without grinding and having to stop to align the gears up in the tcase.

[padresag]

that does sound about right. thanks for storing the info
ron
most 4 x 4's are pavement queens now. I can remember when a bad road was one that you couldn't get through and now if it gets a pothole everyone is screaming
mind you I have only had my hubs in twice when I needed to in 18 years

[LONGHAIR]

Originally Posted by Sinisterspeed

If your looking into doing the 4x4 conversion. Choosing the gear ratio's is much further down your list then you might think. These are easy and fairly cheap to take care of no matter what the ratio's currently are.

I would really know how changing gear ratios is easy and fairly cheap?

[msgross]

Originally Posted by LONGHAIR

I would really know how changing gear ratios is easy and fairly cheap?

I agree, I found it cheaper to just buy another axle with the ratio I needed...

[zeusflash]

I talked to the GMC owner a little while ago. He had another guy look at the truck today and he turned down a $1050 offer. I told him I was thinking of offering $1000,he said the lowest he would go is $1100. To me that makes the truck an OK deal but not a great deal. Again,I have not been able to test drive due to no brakes so the entire drive train is and unknown. I need to talk to my trans guy tomorrow about changing my Turbo 400 output shaft and the availability of a 400/205 adapter(this will determine the possibility of the 427/turbo 400 swap). I know,I know I'm being pretty cheap,but with a 9 month old baby to think about now I kind of have to be. Thanks for all of the input and I will continue to look forward to more of your comments. Updates to follow........

[Sinisterspeed]

Usually when doing a 4wd conversion your not going to be running a stock tire size anyhow. Once your truck is set up you can drop it off at the 4x4 shop usually for 750 bucks and have the gears changed to what ever you want front and rear once you had decided on how you truck will finally be set up and what it will be used for.

Richmond gears usually are around $136 an end. Lockers and carriers are where your money goes when your talking 500+ for a Detroit to fit a 60 or a 14 bolt 350+ for a trac lok its better to use the one you have if it has a locker or factory limited slip or find one that does. Then just change the gears rather then going with the cheaper find another axle route which could mean bad brakes that need tending to as well as loosing the locker that you have in your axle you can usually go from 3.73 to 4.10 without buying a Carrier or 4.56 to 4.88 same thing. I personally have tried the "just buy another axle" route before it cost me way more then the 136 bucks for the gear set and 150 bucks to have someone set it up. Now when you start adding new bearings (that either axle may need) or a locker; carriers can usually be had at any wrecking yard for under 70 bucks if your needing to change to something drastically different from what came in the axle in question.

As I was saying to start with it is further down your list of priorities then finding all the parts you need first to pull the conversion off in the first place. How much would it cost to buy all the parts needed separately or things you might have forgot about like the adapter and new transmission you will now need. there are many ways to go about this as well. You can use a divorced transfer case and eliminate the need for the new transmission. Yet you would have to make a new cross member, build a special driveline to go from a slip yoke 2wd trans to a u joint input of the t case. eliminating the need of the trans/transfer case set up. If you chose this route you could use one from a Chevy,ford or a dodge each with different consequences. Although it would now invoke new costs. Thus better to stick to what you can find if you can complete the project. You could use a ford mounted NP205 with the output shaft on the wrong side. but this would cause you to have to run a ford front axle but this would give you the ability to run a high pinion 44 with crossover steering factory thus eliminating your possible 700 crossover steering you may be planning on doing. You can also get dodge stuff that look vary similar to a Chevy set up some even coming with 4.88 gears stock but the pumpkin is mounted 1 inch or so to far over to make it ever mount up correctly on a Chevy.

So I stick to what I said in the first place. The gear ratio is much further down your list of priorities then you might think. Finding all the parts in one place (like a donor truck) is much more important then worrying about the gear ratio. It can be fixed later for alot less then fixing one of the above mentioned things that do happen and most likely will need to be changed to accomplish the desired finished project anyway.

[msgross]

$750 might be cheap for some, but not most...

I paid $35 ($75 in brakes and seals)for my 3.73 12 bolt with posi and have about $150 invested in the front 10 bolt (new bearings, ujoints, calipers and pads)

[Sinisterspeed]

Ok I agree, I just took it for granted that if someone was entertaining the idea of doing a 4wd conversion there budget better not be 150 bucks or it is IMHO your looking the wrong direction. this conversion will never be completed for 150 bucks.

[Sinisterspeed]

using a 10 bolt in the first place is something I would never do anyway. There is a reason it is cheap. In fact I had one around here for a couple of years I had the scrap guy come get cause nobody would take it. This goes the same for the closed knuckle dana 44 I had with 4.56's in it.

If you were going through all the trouble of doing this conversion why not find a match set of axles for around 250-350 out of the paper or from a non running truck.

This is just turning into something that its not supposed to be. HEY if you want a 35 dollar axle in your truck go ahead forgive me trying to offer any advise.

[padresag]

you can use an independent 205 from either a dodge or an IHC as both are for the pass. side mount. the only difference with the dodge you have to change all the yoke over as they are different.I used one from IHC scout biut the 205 was also used in their p/u. I used the comb of the t221 and ihc mounting to install it
ron

[Sinisterspeed]

Originally Posted by zeusflash

I currently own a 69 3/4 ton 2 wheel drive pickup and want to do a chassis swap to four wheel drive. I have been searching for a 71 or 72 3/4 ton 4x4 to donate the chassis. So far I have not had much luck. Today I went to look at a 72 GMC 3/4 ton 4x4. It is on the Spokane area Craigslist offered for $1350. The GMC has an automatic trans,power steering,power brakes,some A/C and rust,the bad has been swapped and is very solid though. The big dilemma is the cab. It is an A/C cab and also has running lights so I am considering doing the rust repair and using the cab. My understanding is that Chevy and GMC cabs are the same(and I need the high hump floor anyway). Is this correct? The other question is about the rear end. My 69 has a HO52 with a locker which I would like to use. The GMC has a Dana 60. Will a leaf spring HO52(2 or 4wd) bolt to the springs in place of the Dana 60. I suppose the Dana could be limited slip but I don't know since the SPID tag was gone. My 69 also has a 427 and a Turbo 400 in it so a motor and trans upgrade may also happen. I think that I could get the GMC for $750-$1000. Any answers,thoughts ,opinions would be greatly appreciated, especially from you guys who have done this type of swap.

zeusflash your heading in the right direction in my opinion. This is the easiest fastest way to get to the finished project. As I was saying earlier in the thread you could use the HO52 if you wanted but it would most likely save you grief and expense if you just used the one from the donor truck to get it together at least. Keep your HO52 until you figure out what your ratio's are and will be when your done to see if maybe you only need to change one axle to get your desired ratio or if you have to do both anyway then use which ever axles you want. As far as the cab its up to you. You can use the small hump but you would have to install the trans and tcase together as you cannot reach the top bolts between them unless you have a body lift then it wont matter either way. MSGross had talked about his axle on his K10 that he was into very cheap. You are looking into 3/4 ton stuff much better and much stronger thus cannot be had for the prices he was quoting from his experiences. I have done this using 1/2 ton dana 44/60 , had a 10 bolt 3/4 front (junk) matched to a Dana 60 rear, 3/4 ton 44/60 and now 1 ton dana 60/corp14. Bank for the buck you cant go wrong with what your looking at. 3/4 ton 44/60 can be had pretty cheap and its pretty strong. I have never broke a 60 rear myself running tires up to 40" posi with 500hp BBC and burning em off on dry pavement. OH, it can be done also with a 73-87 chassis but the frame jogs are different so the need for some fab work will be needed. I just used the axles out of em when I have done it. Best way to go is what your doing IMHO stick with 67-72 3/4 ton 4x4 for a donor and you will cruise right through it since mostly its all bolt on anyway 2wd or 4wd.

[zeusflash]

Went over with my body guy(who is interested in putting together a 2wd out of whats left of this project)and looked the the truck again. I made a deal for $1000 for the 72 GMC. Looks like the body swap is on!!!! Going to bring it home Saturday. I will post some pic this weekend. Looks like I have some work to do this winter...build two trucks!!!!