Hello Folks,
I have just completed a 4 wheel drive conversion on a close budget.
I wanted to get this on the forum before I forgot how I did it and the problems I encountered.
The truck I converted; 1988 F-150 Long bed, 4.9 straight 6 with a t18 4 speed transmission and 3.55:1 limited slip rear.
Yes, I know that tranny was not stock in this truck, I converted the truck from a C-6 auto to the T-18 awhile ago. I will do a separate post on that.
To do this conversion you really need a donor truck because there are so many parts you will need off the truck, best you own it. I found a guy selling a rotted out 1987 F-150 for $600.00, the truck had a 4.9 6 cylinder, and an NP435 4 speed tranny, a 1356 transfer case and 3.08:1 rear, the front axle was a 3.07:1 The rear was not limited slip. This truck ran and the 4 wheel drive worked fine in high and low range, per me test driving it. Don't buy a non-running truck that you can't test the drive train out on. Very important for getting this done on a budget. Make sure both trucks have the same wheel base measurement. Both the trucks here were long bed, regular cab, I did not measure, but took for granted that the wheel base was the same on both. Try to find a donor truck with some good items on it you can sell locally or on e-bay. More on this later.
I started by calling local scrap yards to make sure they could haul away a truck with no wheels or axles. Found one that would flat bed it and give me the scrap value for the truck. (When I did scrap the truck, it weighed only 1800 some pounds.)
Next, put the donor truck on a solid surface so you can safely jack up both ends, high. You will need some 6x8 x at least 5 foot long, and a few pieces of 4x4 will help as well. and I suggest two scissors type jacks and keep in mind access for a flat bed to haul it away when you pick your spot to strip the truck.
Time to strip the donor truck, I removed all sellable items, this one had a real nice bench seat with no rips, skull shifter ****, floor mats, etc.
Then remove the tranny and transfer case shifter levers and you will need the pan that is bolted to the floor that the shifter levers come through. Remove the dash and un-hook the speedometer cable, you're gonna' need it. Careful with the shifter boots as well.
For the underneath parts, I started with the truck still safely on the ground with wheel chocks and removed both drive shafts, unhooked the speedometer cable and 4 wheel drive switch wire from transfer case. Also unhook the reverse switch wire from the tranny. Keep these connectors and wires. Remove all the crossmember bolts and tranny mount bolts and nuts. Remove transfer case, then the tranny. To the rear, cut the rear rubber brake line, remove the parking brake cables, loosen the U-bolts holding the rear axle to the leaf springs, unhook the speed sensor from the rear end, Off to the front, remove the front lower shock bolts, the top coil spring retainer bolts, and loosen the radius arm nuts. I then separated the steering link from the truck by removing the drag link from the pitman arm. I cut the rubber brake lines to the front wheels.
I set up my jack by centering the 6 x 8 wood on the jack saddle, then moved the jack till the 6x8 was across the bottom of the truck just a bit behind the radius arm nuts, once the jack was set, i removed the pre-loosened radius arm nuts. then jacked the truck up far enough to wheel out the entire front end. place a 4x4 length of wood under the radius are brackets and lower the truck onto that. (this will be a help to the flat bed driver)
Remove the rear end u-bolts and jack up the truck just high enough using your 6x8 again, to free the rear end and wheel it out, let the truck down on some wood and call the scrap yard.
The converted truck: Same as the donor truck, first I only removed my front end parts. No need to unhook the brake lines, just remove the calipers from the wheels and hang em' up with wire, out of the way.
Your original rotors, radius arms, springs, wont fit anymore. Sell em' or scrap em'.
After all the font end parts were removed from my truck, and after inspecting the u-joints, etc on the "new" unit, I removed the wheels, and dragged the assembly under the truck, mounted it up as an assembly and re-installed the calipers. Use new radius arm bushings, nuts, and washers.
Mount up your shocks, my original shocks worked fine. Hook up your steering. I had quite a bit of trouble getting the springs and the radius arms to line up at the same time while trying to keep the right drive shaft from separating. Don't start with the radius arms.---------------- The problems I encountered doing this; I could not loosen the bolt and nut that goes through the axle, radius arms and holds the bottom of the coil springs.When you're working with 15 year old vehicles you have to expect problems like that. Had I been able to loosen them, the install would have been much easier. Expect allot of work and cussing. After that was mounted, of course the front end now sits nice and high, OH YEAH!! I drove the truck to see if there were any problems with the new front end.
Then time to change the rear end ring and pinion gear to match the front end. This is a fairly straight forward job and there are some videos on you-tube to help out. ------------Problems encountered Of course the bolt holding the small shaft that keeps the axles from moving inward for c-clip removal was broken. I got real lucky though in that even though the bolt was broken, it dragged the the other half of the bolt out past the threads letting me to remove it with just a magnet. Whew!! You can avoid this whole problem by using the whole rear end taken from the donor truck though. I wanted to keep my original rear housing etc for a few reasons, starting with the donor truck's rear was painted, sloppily, with a brush of some kind, using DOT road paint. That is some tough thick paint!

Ok, now we have the front axle installed, the rear matching gears installed, and all are working, and the 4wd hubs seem to function fine as well. No noises or problems.
Now I installed a new front shaft seal on the tranny, new input shaft seal on the transfer case, and a new seal on only one of the transfer case output shafts. Since I cleaned and painted both items, I knew which seals were leaking. Because of lack of availability, I had to make the gasket that goes between the tranny and transfer case. I also had pulled off the PTO cover on the tranny just to check for metal parts laying in the bottom, and look at all the gear teeth. I had to make that gasket also because to buy one you have to buy an expensive gasket/seal set.
I then had to have the u-joints on the rear drive shaft replaced and the rear flange switched from my original to the "new" drive shaft.
While a machine shop was doing that I switched out the trannies and
added the transfer case. You will need to use the crossmember and supports from the donor truck here. The 4 wheel drive crossmember is very different from the two wheeler version. Be careful when bolting the transfer case to the tranny, don't over tighten or you will strip out the threads on the x-fer case.
As soon I I got both drive shafts back with new u-joints and flange switched, I installed them, installed the shift levers, "new" floor pan from the donor truck, reassembled the interior, I had a working 4 wheel drive truck, yoohoo!!!
Still work to do though, the donor truck speedo cable has to be installed, it's longer because it hooks into the x-fer case instead of the tranny.
I pulled the dash cluster to do that end of the cable, and while I had it out, i checked to make sure the dash panel had the 4wd and the low range words, then replaced all the 194 bulbs and made sure to put one in each of the spots for the 4wd and low range indicator. The wires are already there hooked to the cluster. Under the hood on top of the rear of the driver side wheel well sits a connector with 2 light blue wires just waiting for you to complete the circuit to the transfer case, using the connectors you kept from the donor truck.

NOTES:: PLEASE READ:: An impact gun of decent quality is really needed for this job.
I found out, after purchasing the donor truck, that 1987 and early 1988 4wd trucks have the dreaded "top hat" flange mounted 4wd locking hubs. There are no service kits or replacement parts available for these hubs. They are subject to damage from heat from heavy braking or a sticking caliper. Even though my hubs are working fine, I am going to convert the front end to the 80 to 86 or 89 to 92 type. It requires a ****load of parts best taken from a junk yard. See Jeff's Bronco Graveyard for info on that. Long story short, avoid 1987 and early 1988 trucks as your donor truck.
After selling everything that would sell like the seat, tool box, wheels and tires, shifter ****, and scrapping whatever was left, I got the cost of the donor truck down to $156.00, and I am still holding a bunch os spare parts as well. The total cost of this conversion to me was under $500.00.
Things you will need to purchase new:
Seals for x-fer case and tranny, u-joints if needed and the cost to have them pressed out and in, a new shaft lock bolt for the rear end if you do what I did or a new rear rubber brake hose if you change the whole rear out. New radius arm bushing kit, new 194 bulbs for the dash cluster, new fluid for the rear axle, front axle, tranny, and x-fer case. The 1356 x-fer case uses Mercon auto tranny fluid, the tranny and axles use heavy gear oil. A 8x6 length of wood, high heat paint if you're so inclined, and that is all I had to purchase!!
The front axle I took from the donor truck had 2 shocks on either side while my truck had only one per side. The conversion worked just fine using only the rear shock, one per side, hooked up. I will have the lower front shock bolts removed soon.
I hope this is a help to someone wanting to do this conversion, and I hope I have not forgotten anything important. E-mail me at coronet25@comcast.net if you have questions.

 

Greetings! You covered a helluva lot of material! If anyone is considering doing a similar job, the "read" will be well worth the time! I did NOT have that time available, but could not resist complimenting you!

Did you use twin I-beam suspension? I missed that point, and a few others. And, a few other questions:

Do you favor, or dislike, the alloy, split-housing types of transfer cases, having chain-driven front outputs? They ARE light & easy to handle.......

impish

 

Great info, thanks.