Who knows about 1970 J4000 4x4's?

[Rusty]

Can anyone tell me much about the model stated above? I have an opportunity to buy one for about $750. It is supposed to have a 350 V8, 3-speed manual, 4x4, and be 3/4 ton. I know very little about these trucks, but it is in working order, but the bed has been replaced with a wooden flatbed. I am only interested in it for an offroad rig. Is this a bad platform to start with? I just like that possibility of having the 3/4 ton axles. If I get it, more than likely there would be some major fenderwell cutting. How well do these rigs articulate? Is the J4000 SOA or SUA from the factory. Any and all comments as to performance, buildability, and dependability appreciated.

[Bob Barry]

Well, the J-4000 designates the long-wheelbase pickup (GRVW varied, from half-ton to heavy-duty 3/4 ton). Replacing a rusted bed with a flatbed is a common procedure.

It is a fine platform to start with if you don't mind custom-fabricting things like springs and shackles, since there is no aftermarket support for the earlier J-trucks. Aftermarket lift-kits are readily available for the '74 and up trucks (they revised the suspension that year), but unavailable for the earlier ones.

A couple other drawbacks to the early models is the closed-knuckle front axles and the drum brakes. They'll work, but again, not as well as the '74 and up trucks with open-knuckle disc-brake front ends.

Oh, yeah, the earlier trucks lack a proper fusebox, so the wiring is pretty primative.

But the drivetrain is strong; the Buick 350 is a solid motor, the D20 transfer case is a cast-iron gear-driven case, and the D44 front axle is probably paired with a D60-2 rear axle (not full-floating, and not the largest shafts, but no weakling).

If you have 5-lug rims on there (most likely the case), you can use rims made for Fords and CJ jeeps.

Oh, and the front suspension on the J-trucks, but not Wagoneers, is SOA until '73.

[joe]

Rusty, I pretty much agree with Bob B's reply except his view on the closed knuckle front axle(which yours does have). I've owned far more closed knuckle equipped 4x4's than open knuckle ones and I like'm. They're reliable and tough providing it's been maintained over the years. The knuckle needs to be kept packed with grease and this is where owners screw up. The seals get dried out and they leak down and then someone fills them with gear oil instead of grease and they leak even more and faster. But the closed knuckles are easy to work on and maintain. The only draw back I find with them is your turning radius is larger. So far as the drum front brakes go the trucks run 12" compared to the Wags 11". Admittedly the 11" are a bit weak but both my trucks brakes are very good especially the one I did a complete brake job on. If the brakes are in good condition they're as good as any another drum braked vehicle.
So far as 1/2 or 3/4 ton goes look at the VIN and decifer it here in the /tech/ section of this site. J-4500's are 5000 GVWR, J-4600 is 6000 are both 1/2 tons with the J-4600 being a "heavy 1/2" ton. The later using a D-60-2 semi-floater rear axle which is also used by the J-4700(7000 GVWR). The J-4800(8000) used a "full-floater" D-60.
Drawback to the D-60-2 is parts are getting scarce. I had a heck of a time finding axle bearings and retainers and had to have one retainer made in a shop.
What you're looking at in a 1970 is a tough truck but expect parts finding hassles. My $0.02 on the motor(350 Buick) is that it's the best one ever put in FSJ's. Good luck.

[jeepbob]

Rusty,
I have a j3000 that is a 70 and it is where the axles for my Wag are coming from. If it has 8 lug rims then it has a full floating rear D60. I prefer the closed knuckle frt ends to the open in the deap mud as the goo does not get into the frt steering u joints. Also there are not any ball joints as the king pins use tapered roller bearings. While you do use lose some turning radius it is not a huge amount. Some people will say that the 19 spline axles are weak, but I have never had a problem with axle shafts on my D27 (spider gears yes, axle shafts no)and those are not as strong as the 19 spline D44's.

[ September 22, 2001: Message edited by: jeepbob ]