How well should compression hold the truck?

[KD4UPL]

Currently the parking brake doesn't work on the truck so I've been leaving it in gear when parked. Last night my son drove it and stopped it on our mildly angled driveway in 1st gear. It stated very slowly rolling back down hill. In testing today even in Low the truck will very slowly creep backward down the hill. I was in the seat. My son was watching the engine pulleys with the hood up. He said the pulleys were very slowly turning as the truck crept backward. This is the first manual vehicle I've ever owned. I always though the engine compression would hold the vehicle, at least on a mild angle. Should be using Reverse gear to hold it if the downhill direction is backward? Is the engine just worn out with too low compression to hold it? I'm asking too much of engine compression?

The truck is a 1986 K10 with 4.3 V6 and SM465. 3.08 gears and 33" tires. Very soon, I hope, the gears will be changed to 4.10. I'm thinking the axle gear swap should help the engine hold the truck better. I guess I really just need to get the parking brake fixed.

Thanks for any input.

 

[Ricko1966]

It depends on the gearing,the compression ratio,and the degree of the angle as to whether or not the engine will hold a vehicle in gear.

 

[Radiohead]

Dadidadit. Fixing the parking brake is the least expensive option. A wood block is also an easy peasy work around until you get the rest sorted out.

73

 

[Terlingueno]

I was taught back in the day to always have our truck in gear when parked, engine off. And that if parked facing downhill to put the transmission in reverse, if parked facing uphill, put it in 1st. I have always done this. And use the parking brake on both...

 

[Sad Sack]

I was taught back in the day to always have our truck in gear when parked, engine off. And that if parked facing downhill to put the transmission in reverse, if parked facing uphill, put it in 1st. I have always done this. And use the parking brake on both...

I always use the e-brake and curb. No curb, I fix it so I don’t worry about it.

 

[Terlingueno]

I always use the e-brake and curb. No curb, I fix it so I don’t worry about it.

Yeah. I remember that from driver's ed. The only place in the whole county with curbs of any kind, is in 'town' and it's pretty flat there. Additionally, I have always had/driven 4 speed manual transmissions. Never have owned an automatic. The 1950 GMC truck I learned to drive in was a 4 speed manual. My Dad's 65 c20 was a 4 speed. My 65 Suburban, 79 CJ-5, and the Sub I currently drive all 4 speed manuals.

 

[Turbo4whl]

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Wheel chock, $14 at Harbor Freight.

 

[KD4UPL]

Thanks for the replies. I stuck some checks in the bed. Hopefully when they change the gears I'll get them to fix the E brake. The lower gears should help as well.

 

[TotalyHucked]

I would definitely fix the e-brake ASAP, it's cheap and simple. In the meantime, definitely use wheel chocks. Right before we moved into our new house when I was 7, our neighbor across the street had a very steep driveway and at the time had a Geo Tracker that the parking brake didn't work. One day, the trans decided it'd had enough and sheared the teeth while parked, it went flying down backwards, across the street, down our side yard hill and into the mud of our back yard. This was only a month or so before my parents bought the house.

Then years later when I was in HS, I was in the garage working on my IROC with the music going but kept hearing this weird chirp every so often. When I finally turned off the music and looked outside, their Jeep Wrangle (same neighbors) was slowly inching it's way down the driveway. Compression would catch it each time, but it would bleed off and let it roll back another few inches. So I ran over, hopped in and yanked the e-brake as hard as I could. Then knocked on the door and told them about it lol. I think they finally started using e-brakes properly after that.

 

[Sad Sack]

I would definitely fix the e-brake ASAP, it's cheap and simple. In the meantime, definitely use wheel chocks. Right before we moved into our new house when I was 7, our neighbor across the street had a very steep driveway and at the time had a Geo Tracker that the parking brake didn't work. One day, the trans decided it'd had enough and sheared the teeth while parked, it went flying down backwards, across the street, down our side yard hill and into the mud of our back yard. This was only a month or so before my parents bought the house.

Then years later when I was in HS, I was in the garage working on my IROC with the music going but kept hearing this weird chirp every so often. When I finally turned off the music and looked outside, their Jeep Wrangle (same neighbors) was slowly inching it's way down the driveway. Compression would catch it each time, but it would bleed off and let it roll back another few inches. So I ran over, hopped in and yanked the e-brake as hard as I could. Then knocked on the door and told them about it lol. I think they finally started using e-brakes properly after that.

Agreed, I remember when Fords had a problem with their trannys slipping out of gear and creating dangerous situations, I took note and I use e-brake every day on a slant or flat, doesn't matter. If one can remove the strain on a trans, it's a win-win.

Ford Transmissions Failure to Hold in Park

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www.autosafety.org

 

[Jrgunn5150]

My 68 F250 has never held itself in place in first, I've been using reverse since 1994 lol.

It's also never shown oil pressure on the gauge when warm.

 

[DoubleDingo]

I'd say your compression is very low. Could be high mileage, or bad valve guides and seals. I've used granny low to keep various trucks from moving without issue. The one with the highest gear was 3.54, but it had an sm420, so granny low is very low. SM465s are very similar ratios.

I've shared this story before, but this the perfect thread to share it again.

Dad passed away, I got his 79 K15 Sierra Grande. He drove it around everywhere while drinking on the backroads, low speeds and prone to lugging it in 3rd and 4th gear, so the top end wore out due to lack of oil flow. The engine ran great, but burned percentage-wise more oil than gas. Going down long grades that required using gears to keep the speeds slower, the oil would suck into the cylinders and would send smoke rings out the exhaust. Once on flat ground and throttle was needed it would smoke screen like Spy Hunter for at least a 1/2 mile.

One day my cousin and I went to play golf. The wind was howling out of the west, easily sustained 20mph with gusts much higher. I always put it in granny low when parking it and it held just fine with 3.73 gears, but if it was a steep grade I would engage the parking brake. This particular time, though, I drove into the "parking spot" and since it's maybe 2 percent grade, I left it in 4th gear and no parking brake.

We wanted to grab a beer and some snacks after hole 9, so I drove the cart around the clubhouse and my truck was gone. I looked again and saw it was parked across the parking lot. So, I grabbed the $5 from the ash tray and locked the doors this time, got us beers and snacks, and we played another 9. (I actually used the wind to make a putt that day, that's how hard it was blowing. Just tapped it and let the wind take it to the hole.) I left the truck there, and when we went to leave after our round I looked closer and saw marks on the propane tank and saw it had been shoved into the building. I looked even closer and realized that the wind had pushed the truck across the parking lot, and it gained enough momentum to roll up onto the railroad tie bump stop planter edge, into the propane tank where the bumper bolts scraped the paint off the tank, then rolled back off the tank and railroad tie, and stopped like it was parked there intentionally.

I told the manager that was working there, they looked, said no big deal, and we left. Never got a bill, which I was surprised about, and there was never another word spoken about it from the golf course staff.

This is the dirt area I parked the truck, and the path it took into the tank...
Seeing the golf course in disarray as shown in this photo makes me sad. It was such a nice course when I grew up there.

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[Blue Ox]

Even with an automatic in Park you're not supposed to use the transmission to hold the vehicle on a grade.

Leaving it in gear on level ground is fine, but trusting the drivetrain to counteract gravity is just bad practice.

Fix the parking brake.

 

[Rustisbest]

Funny story but wasn't at the time...winter time a few years back we got a few inches of snow and ice. I made the mistake of setting the brake on my Tahoe after coming home from work like I always do. When I went to leave the next morning, it wouldn't move either direction. I got aggravated and put it in 4 low/reverse and dumped the clutch to break it loose. Rolled up to the first stop sign and the brakes went to the floor. Only had a couple miles to go so I just eased it on to work and then back home afterwards. Tore it apart and turns out it bent the adjuster at a 90* angle instead of just releasing. I dont know if the shoes were rusted to the drum from the magnesium chloride they put out or if it was the temp swing that had it bound up. I dont use the brake anymore when it snows lol.

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[Blue Ox]

Funny story but wasn't at the time...winter time a few years back we got a few inches of snow and ice. I made the mistake of setting the brake on my Tahoe after coming home from work like I always do. When I went to leave the next morning, it wouldn't move either direction. I got aggravated and put it in 4 low/reverse and dumped the clutch to break it loose. Rolled up to the first stop sign and the brakes went to the floor. Only had a couple miles to go so I just eased it on to work and then back home afterwards. Tore it apart and turns out it bent the adjuster at a 90* angle instead of just releasing. I dont know if the shoes were rusted to the drum from the magnesium chloride they put out or if it was the temp swing that had it bound up. I dont use the brake anymore when it snows lol.

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I've had the parking brake on the Mighty TDI freeze in the winter. Since it's FWD and it would just drag the rear wheels I didn't have your option.

A little heat on the drum with a Bernz-O-Matic and you could hear the shoes release.