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Old 09-16-2020, 05:46 PM   #1
dakota1820
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Considering a k1500 gmt 400

I am in the market to buy a 4x4 truck I'm looking to spend about three to four grand which around here you can do but I know it won't be perfect or maybe even pretty. My question is generally related to the IFS how good is it? How reliable is it how strong is it? I've had an old Ford with twin traction beam and it was plenty reliable but it definitely drug off-road a lot and I do plan on doing some off-road activities. I did own a 1990 k1500 for a very short time. But I didn't really have it long enough to play with it much or experience the front end. I've had a few two-wheel drive Chevy trucks from this era and they were great trucks simple to work on cheap to fix reliable. I definitely like the powertrain of the Chevy in the ease of maintenance I'm just unsure about the IFS how does it compare to a Ford or even a Dodge of the same era? What are some things I should look out for?
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Old 09-17-2020, 11:34 AM   #2
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Re: Considering a k1500 gmt 400

Iím not a 4x4 expert by any means, but I actually really like the torsion bar setup. To me it does what it needs to off roading. Now, I donít climb boulders or go through aggressive terrain, but drive the wonderful desert of Nevada and California. On or off road it does great.

The debate has been converting torsion setup to straight axle like the Ford. I have a 2003 F350 and it has the straight axle. The ride is not as smooth and the off roading seems to be equal. I canít tell a difference.

I think itís going to come down to how much and type of off roading youíre going to do. If youíre going to be doing boulder climbing, steep hills, very aggressive terrain, then maybe a straight axle would be better for strength and durability. Like I said, Iím not an expert and my opinions are from just driving the truck.
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Old 09-17-2020, 01:25 PM   #3
1976gmc20
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Re: Considering a k1500 gmt 400

The IFS 4wd is really nice on the highway, and okay off road as long as you're not doing extreme stuff. I use my 89 for firewood and it's managed to go everywhere I've asked it go, including pioneering trails. I have found that those early IFS don't turn nearly as sharp as an open knuckle solid axle, which means lots of backing up on tight turns. All of my old square body 4wds turned really tight, considering the size.

I had to put a ball joint and new CV axles in mine and it still needs pitman/idler so just be aware that any of that vintage might need a lot of front end work. The axles aren't too bad to change except for getting the old ones out. The new/re-manufactured ones that I got from O'Reilly's are trimmed slightly on the inner flange which combined with more flexible boots makes them slip right in from the frame side of the lower a frame. I wish now that I would have just borrowed a torch and cut the old ones in half to get them out.

The TBI versions are about as simple as you can get and still have the benefit of some modern technology. You can start them up and drive away without waiting to warm up a carburetor.

Still, I'm wanting to find 73-87 K/20 in decent shape to replace my K1500, just because I use it more off road than on road, and I really need more than a half ton anyway.
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Old 09-17-2020, 01:48 PM   #4
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Re: Considering a k1500 gmt 400

I drove a k2500 6lug for awhile, it was a pretty smooth ride on road. Now I have a k1500 with 33s. The torsion bars are cranked up and it is a stiff ride on road. There's not much that can be done with the torsion bar set up. I think it's best left stock. I have seen lifted trucks with the torsion bars hanging down under, not a fan of the look.
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Old 09-17-2020, 04:37 PM   #5
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Re: Considering a k1500 gmt 400

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I drove a k2500 6lug for awhile, it was a pretty smooth ride on road. Now I have a k1500 with 33s. The torsion bars are cranked up and it is a stiff ride on road. There's not much that can be done with the torsion bar set up. I think it's best left stock. I have seen lifted trucks with the torsion bars hanging down under, not a fan of the look.
LT235/85R16 makes for a cheap "lift"

But I'm amazed what I can drive over with mine, and it is an xclb with 245/75.
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Old 09-18-2020, 04:04 PM   #6
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Re: Considering a k1500 gmt 400

Oh, I forgot to mention those thermal actuators for the central axle disconnect on the 4wd.

They don't work very well when they work, and then they quit working at all.

Since mine is just a "ranch truck" I just shimmed the end of the actuator to lock the two front half axles together semi-permanently. The ring gear and front driveshaft now turn all the time even in 2wd, just like if you had the front hubs locked in on a solid axle.

They also make a manual cable control kit. The last I checked they were about $160 and claimed an hour or two labor. I figured that was money I didn't need to spend but an advantage is that you would have a 2wd low range option. If I had a nice GMT400 then I would get the cable control.
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Old 09-18-2020, 04:33 PM   #7
dakota1820
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Re: Considering a k1500 gmt 400

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Originally Posted by 1976gmc20 View Post
Oh, I forgot to mention those thermal actuators for the central axle disconnect on the 4wd.

They don't work very well when they work, and then they quit working at all.

Since mine is just a "ranch truck" I just shimmed the end of the actuator to lock the two front half axles together semi-permanently. The ring gear and front driveshaft now turn all the time even in 2wd, just like if you had the front hubs locked in on a solid axle.

They also make a manual cable control kit. The last I checked they were about $160 and claimed an hour or two labor. I figured that was money I didn't need to spend but an advantage is that you would have a 2wd low range option. If I had a nice GMT400 then I would get the cable control.
Good info to have. What is the point of the thermal actuator? Other trucks don't have that , that I know of.
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Old 09-18-2020, 09:43 PM   #8
Russell Ashley
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Re: Considering a k1500 gmt 400

The latest issue of Hot Rod mag has an article about the GMT400 trucks. It doesn't go too deep but it did answer a few questions for me. I just bought a 96 Z71 after selling my 57 chevy truck but haven't driven it due to the rain we've been having from the hurricane.
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Old 09-19-2020, 02:04 PM   #9
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Re: Considering a k1500 gmt 400

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Good info to have. What is the point of the thermal actuator? Other trucks don't have that , that I know of.
There is some sort of dog gear or something on the passenger side of the front differential that disconnects the two front axles. That way the spider gears just get driven from the driver side and the ring gear and front driveshaft don't turn. It's supposed to save gas and wear. The newer trucks have a electro-mechanical actuator that they tell me works fine (I will find out eventually since I bought a 2016).

The thermal actuator is a plunger filled with oil that an electric resistance heater is supposed to make expand and push the axle connector together so you have four wheel drive. Both type have a switch that works off the transfer case lever (or the push button/knob controls). The problem with the thermal is that either the heating element burns out, or if it's real cold like driving in deep snow it doesn't get hot enough to expand properly.

Or so they tell me ... mine never worked, which enabled me to buy it cheap because no 4wd. I just cut a piece of 3/4" PVC about 1" long and jammed it on the end of the plunger to hold the axle disconnect in the engaged position. I did jack up the right front wheel and turn it slightly until it engaged while I was re-installing the thermal actuator. You can feel it lock in and then the front driveshaft will turn when you turn the tire that is off the ground.

It was a "temporary solution" to see if I could get the 4wd working before I spent any more money on the old pickup, but it's been that way I think about seven years now. If this was a nice pickup then I would $pring for the cable control kit, but the farthest I usually go from home is 25 miles one way to the dump, and to fill the gas tank.
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1971 Chevy K-10; 1973 Chevy K-20; 1976 GMC C-20
1977 Chevy C-10 Suburban; 1980 Chevy K-10
1989 Chevy K1500; 1991 GMC V1500 Suburban
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