Troubleshooting 1984 K10 transmission

[Preston]

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i have just brought home a 84 K10 long box, that has been setting for at least 10 years, the good new battery topped off fluids and engine sounds good, a few vacuum leaks but pretty good sounding engine. The bad, the transmissions will go into reverse only, I see fluid on the stick, could be a pint low but don’t think it’s too low to cause her not to go forward. Long day think I’ll do a transmission fluid and filter change tomorrow, and hopefully she will go, I know 10 yrs is a long time to set but, if anyone has any ideas an additive, synthetic fluid, I’m hoping not to have to do a rebuild but, one step at a time. Thanks for your time and advise in advance.

 

[PrairieDrifter]

Change out the fluid and make sure it’s warmed up and cycled through the gears a couple times and make sure it’s topped off 100%.

If that doesn’t work then you’ll probably be out of luck. Not many things that make a transmission fail are simple fixes. Generally ends up as a rebuild or replace.

 

[PrairieDrifter]

What transmission is in it? 700r4? Do you know why it was parked for ten years? Or any backstory to it?

 

[HotRodPC]

Yep, maybe it got parked cuz the transmission was bad so I'd find that out. As far a fluid and filter change, I wouldn't waste the money and time. If it's got reverse, then the filter is picking up fluid. Sounds like the Forward Clutch Drum is fuct. Either the seals are bad from sitting so long and fluid is not able to compress the clutch drum piston, or the clutches are bad in that drum.

So, if the fluid is any kind of red maybe even a hint of brown it'll work. Don't go wasting money, fluids are expensive these days. Best thing to do is let it warm up real good. Let that hot trans fluid run through the transmission. Occasionally while it's running and warming up, garage shift it to R, then D and stay off the throttle. No need to slip the clutches and tear it up. You're just wanting to open the passages and let warm fluid travel to it's destination. So let it sit in D for 10-15 seconds, then go to 2nd, for 10-15 seconds, then to 1st same thing. Then go back to R again, then to P and let it continue to warm up. I'd probably just let it run for an hour doing the shifts every 10 minutes or so. Remember, stay off the throttle. You're trying to revive it, not kill it and allowing clutches to slip, kills it.

What you're hoping for, is that the seals have hardened up from sitting so long and you want these seals to soften up with the heat and trans fluid circulating to the those affected internal seals.

You can also try a good transmission additive. Those do help soften hard seals. You can put up to 2 treatments in it. Don't waste money and try 3 or more. If 2 bottles don't get it, no bottles won't get it and you know it's time to remove the transmission for a rebuild. So if you spend anymore than just 2 bottles of trans treatment, you're wasting your money. If the trans does come around and decided to work, I think I'd leave it alone for awhile and just drive it without changing the fluid for now.

 

[Preston]

Thanks, will do, I keep buying parts trucks and well you know the trucks are tough might bring another one back to life, never know.
Happy Easter

 

[HotRodPC]

Nothing wrong with buying parts trucks for cheap and fixing them. I bought a 85 K1500 with a new crate engine and 10K miles on the new engine and a brand new 10 minute old battery so they could get it started for me to hear it run, but it had a bad transmission so I picked it up for $500. Rebuilt a transmission for about a $100 in parts installed it, drove the truck for a year or year and a half or so then sold it for $2500.

 

[Preston]

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I jacked the back wheels off the ground and have been letting it run at an idle in each gear for about an hour ( ran out of gas) will get som more gas and run it again later. We will see.
Not an hour in each gear, but from gear to gear, wheels turn freely, maybe things will loosen up and start working like it’s supposed to.
I also found a wire coming from the starter that the rats or something chewed in half, hooked it back and wow the radio works. Anyway it’s a work in progress, all the original parts are there, smog pump, catalytic converters, “Y” pipe vacuum hoses everywhere. Don’t usually find a truck that someone hasn’t pulled everything off of it.

 

[PrairieDrifter]

For sure, those are the ones I’ve looked for and acquired myself. I don’t look at ads for “mud trucks” and with aftermarket accessories and gauges and crap, especially wiring jobs.

I like to start with the basics from factory, you can remove all the emissions junk, go through the things you know will need some work, then you can build it the way you want and not lose out on a bunch of money.

I don’t like buying other people’s cheap projects cuz everything is usually a hack job and way more work.

Farm fresh trucks are the way to go, you got to be careful with some of them cuz farmers have some undesirable ways of doing things but most of them take good care of their things and don’t do any modifications.

I bought my suburban for 500 bucks, had some issues but it’s running and driving on the road with most of its original drivetrain just all freshened up with new seals and gaskets. It’s got some rust that can be fixed easy.

You can find really clean trucks for cheap with bad transmissions quite often. That’s usually why a lot of them get parked and eventually sold. Just gotta wait for the right one.

From the looks of it your truck looks pretty straight!

 

[MylesNT]

Once upon a time, I filled the transmission in my truck with water. I ran a case of transmission fluid through it to get the water out. When the fluid was nice and red, I set off. About 50 miles or so later as I was going up a hill on a powerline, it was just like you put the truck in to neutral.

That was the end of that transmission.

It had reverse though, that's how we got back to the main road, and eventually, on to the trailer that got it home.