86 Chevy Silverado Suburban, diesel, 4WD.
The truck ran fine before leaving it parked unattended for a week. Now it won’t move. Starts fine, and at first glance seems to shift into reverse and drive fine, but no movement. A little torquing/twisting when rev’ing–like when you rev with the parking brake on–but parking brake doesn’t feel unusual and looks like the cable is moving. Odd thing is, the truck won’t even move when pushed from the front or back while in neutral, even when both transmission and transfer case set to neutral. The other odd thing is the shifter can be moved even when the brake isn’t pressed. I know many cars won’t let you do that, but honestly it’s such force-of-habit for me I don’t even remember if this truck used to do that or not. Could be just a little quirk, like the key coming out when the ignition still runs (that one is quite a handy quirk, actually), or could it be a sign of a bad linkage? Seems odd for that to happen, though. Fluid level and color appears ok in the transmission, but only by the dipstick-- I haven’t drained it to check for water or metal shavings or anything like that.
So what’s my next step? I only have a small amount of time each day to work on it, so I want to make the most of tomorrow. Should I first jack it up to see if the wheels turn better off the ground? (it’s a heavy vehicle, so I’m not 100% confident in the push-test, though usually it would move at least a little being pushed.) Maybe check the brakes? Someone said if the brakes or locked to reset the proportioning valve…does that even make sense if it was just sitting there? Should I flush the transmission fluid? Check the differential fluid or the transfer case fluid? Is there some other test I’m not thinking of?
Many thanks in advance!
I’d guess it was raining about a week ago. The pads likely are rusted to the rotors or the parking brake cables are rusted internally. Neither is unusual, they just need to be freed up.
I’m guessing it’s brakes too. Stuck calipers or parking brake.
Jack the rear wheels up to see if they will turn. I can’t imagine all that torque being unable to turn one of the wheels. The shift lever operation leaves me questioning whether moving it actually changes gears.
That truck doesn’t have a shifter interlock, so it will shift without the brakes being applied. You should be able to hear a somewhat metallic ‘click’ between gears when moving the shifter. If it’s in the transmission, it would seemingly have to be slip. The engine would rev freely when in gear. I also suspect a brake problem. Jack up each front corner of the truck and try turning the wheels by hand. For the rear, raise up both wheels for this test, as it may have a limited slip, which could be deceptive if you check one side at a time. Be sure to use jack stands also, so you can post back.
Having the transfer case in neutral should completely disengage the drivetrain from the wheels so it should roll even if the transmission is in park. I’d definitely lift up and spin the wheels-- start with the back ones since they’re the most likely to be the problem.
You might first try putting it in low 4 and trying to move it a foot or two. If it is just a shoe rusted to the drum, that should probably break it loose. Just give it a tiny bit of gas (diesel? the right pedal)-- too much might break something if there’s something else binding up (plus if it does break loose, you don’t want to crash into your house).
Thanks to everyone for their help! I managed to get it sorted out in one evening!
From a quick glance there did seem to be more rust on the front discs than I would expect, so maybe some water while I as away. I did what the majority of replies suggested: I jacked up the rear and tried to spin the wheels by hand in neutral with the parking brake off. Started with the drivers side, which if it was water would have gotten the lesser of it. It was indeed stuck, but had just enough give so that I could wiggle it free after a few hard twists by hand. Once it was turning freely, I was a bit more confident this wasn’t so bad. I could see the driveshaft turning when I turned the wheel now. However, the passenger rear wheel wasn’t so easy. I could already see from the drivers side when I turned the other wheel that it wouldn’t budge (you know how when both are free the diff will turn the other wheel in reaction). I went over to the passenger side rear wheel and tried to turn it manually. It was seized hard! I through my weight into it, couldn’t budge it. I tugged on the parking brake cable going to that wheel (pedal off) and it seemed ok. I pumped the parking brake hard a few times to loosen things, but no go. I put the transmission in park and tried to wiggle the seized wheel by going back and forth on the other wheel, but I was putting enough force on it that I was starting to worry about wearing on my pawl, which already has more give than I like. I couldn’t think of any way to use the engine to advantage in this situation. So I tried a few forms of manual mechanical advantage-- a small lever and the BFM (Big Friggin’ Mallet), but couldn’t really get good leverage. Thought about some brake cleaner, but didn’t have any. Had some Naval Jelly, but it was pretty old. As a ditch effort for he evening, I tried putting it in neutral, spinning the good wheel really fast by hand, and then running to the cab and slamming on the parking brake. Lo and behold! That freed it! I still don’t know why, I’m guessing the parking brake was what was stuck and all that pumping before had it close to giving way, or maybe because of the way it was stuck the brake on the free side caught first and transferred all the momentum to the right side.
She wasn’t too happy about being woken up after such a long slumber (and the temperature is starting to drop here), but she finally managed to start and I drove around the block a few times, carefully testing the brakes. Little rough on the first couple brakes as the rust or whatever wore down, but now she stops perfect, except there is a bit of a shutter even still if I stop on the parking brake only. Not usually stopping on the parking brake, I’m not sure if that’s normal?
Also, should I change my fluids before driving much? Someone once told me if you’re ever in any high water you should change your differential fluid, but that seems like overkill… Still not sure how high the water came or for how long, although it definitely didn’t get as high as the cab. If I should change it, I’m definitely flushing the transfer case, too-- I’m very paranoid about that thing, having been through two bad ones this year alone! Most reliable truck ever, except for that one single [all too expensive] part. (Well, that and the glowplug temperature override sensor-- leaves me stranded if I try to start it after more than one hour from turning it off until four or five hours after --but at least that was a cheap fix, I just jam a wire in to bypass it. The model year before doesn’t even have the sensor, IIRC. Going to rig up a switch to the cab when I have some time.)
A prime example of why the PARKING BRAKE should be used consistently.
BTW, that’s all it is design to be: a PARKING BRAKE.
NOTE: if parking a vehicle for more than a week, do NOT apply the PARKING BRAKE. Just block the wheels to prevent unwanted movement.
Not sure I understand why this is an example of why the parking brake should be used consistently-- I use the parking brake every single time I park, and the parking brake was on the whole time I was away. Granted, it IS a pretty good example of why you might chock the wheels an leave the P-brake OFF, as you suggest, if you’re going away for a while. I suspect you’re right, that if I didn’t have the parking brake on, the rears might not have seized. They would probably have just rusted a bit and gotten dirty, and that comes off with normal braking. But anyways, thanks for the tip-- I’ll be chocking the wheels with the P-brake off in the rainy season from now on (provided the chocks don’t get swept away in the floods! 
As for referring to what a parking brake is designed for, it may be designed for parking, but since it only actuates the rear drums it makes a good test for the rear braking. Normal braking only distributes about 30-40% of the force to the rears, so if you’re having trouble with them, it may not be apparent in normal braking. Now as to interpreting the results of the test (i.e the shuttering), I’m relying on more expert advice, since I haven’t done this test before. (Well, I did once, but it was a totally different vehicle-- a little Honda from which a front brake pad mysteriously fell off while waiting in a drive-thru, requiring me to drive home with careful application of the handbrake anytime I needed to stop or slow down.) My guess is the crud on the rotor is still wearing down, or maybe rear-only braking always tends to shutter because of the way the momentum is kind of ‘pulling’ on the brakes rather than ‘pushing’ like the fronts.