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05-20-2023, 08:21 AM #1
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tug test with front hydraulic jacks not retracting simultaneously - 378MBS
Good morning,
Did the first pull with the new truck yesterday, Tucson to Prescott Valley. The Duramax had plenty of power pulling a 17,500 lb rig up the steep grades out of Phoenix. Arrived just in time to unhitch and set up in 60 degrees and steady rain. Haha, just another RV challenge. All good except for an issue while hitching up as below.
Point is, I want to get in the habit of doing a tug test every time I get ready to move.
So I hit "hitch height" which raised the middle and rear stabilizers, then used the front jacks to match the height of the new B&W Companion, backed into the hitch, locked the handle, and verified the jaws were around the kingpin. But when I went to raise the front jacks an inch or so off the ground (concrete in this case) to do a proper tug test the passenger side jack came all the way up, then the drivers side. At this point the weight of the RV was on the pickup. The jacks wouldn't operate simultaneously once the weight had been transferred to the pickup. The jacks do operate simultaneously when the RV weight is bearing on them.
Makes it impossible to do a tug test with the jacks as a "safety net".
Am I missing something here, is there a problem with the hydraulics, or is this normal?
Thanks2022 Solitude 378-MBS-R, 8k axles and disc brake package, slide toppers, dual panes, 5.5kw Onan, W/D, 3rd AC/heat pump
2023 F350 Lariat DRW on order, (canceled)
2023 Chevy 3500 LTZ long bed Duramax, 12250 GVWR, 3867 cargo cap, Z71, 5th wheel prep
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05-20-2023, 08:35 AM #2
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It's normal, due to the way the hydraulic system operates. The legs are daisy chained so they work basically sequentially. The one with the least resistance will raise/lower first until it stops, then the pressure will force the other one to operate. So when both are on the ground they will raise together as the pressure is equalized between them.
Howard and Peggy
2019 Momentum 351M, and 2018 RAM Cummins dually 6-speed.
His: 1999 Honda Interceptor
Hers: 2013 Spyder ST-S
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05-20-2023, 09:05 AM #3
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That's the way they act.....like my mid-bunk has 3 hydraulic slides on one switch. They operate sequentially too.
Doesn't help with the tug test though!
Thanks2022 Solitude 378-MBS-R, 8k axles and disc brake package, slide toppers, dual panes, 5.5kw Onan, W/D, 3rd AC/heat pump
2023 F350 Lariat DRW on order, (canceled)
2023 Chevy 3500 LTZ long bed Duramax, 12250 GVWR, 3867 cargo cap, Z71, 5th wheel prep
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05-20-2023, 09:34 AM #4
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- Jul 2021
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I believe some trailers have a valve you can close to force a cylinder to not operate. I've seen them, on ours, but never messed with them. I also have the B&W hitch, have had one for over 15 years, and I've never done a pull test. If the handle comes back, the hitch is latched. I drove for over a mile one time with the handle not pinned, not on purpose, but does show that it was locked. Just a good example of the excellent design of the B&W hitch.
Howard and Peggy
2019 Momentum 351M, and 2018 RAM Cummins dually 6-speed.
His: 1999 Honda Interceptor
Hers: 2013 Spyder ST-S
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05-20-2023, 10:12 AM #5
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- Feb 2018
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- Northern California
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I also have a B&W. Most people don't tug test, but I do. After hitching the truck to the trailer I will bring up the landing gear. As said, one will rise before the other. When the second comes up about 1/2 inch I will hit the extend button, the first one that retracted will lower, the other will not move. I stop it at about 1/2 inch. Do the tug test, hit retract all and I'm on my way.
Hope this helps, if I made it clear.Paul, Sue & Wonder Dog Zane
'18 Solitude 310 GK
"15 F-350 6.7, DRW, CC
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05-20-2023, 10:13 AM #6
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Our Solitude works the same way. After hooking up and confirming the hitch lock, I raise the front jacks until one is about one to two inches off of the ground. At that point, they are both unweighted. I squeeze the brake controller to lock the trailer brakes and do a careful tug. The RV is not going to move and the most it would drop is 1 inch or less. Obviously, my foot is ready on the TV brake to stop quickly so I don’t pull too far from the RV hitch plate in the unlikely event the hitch lets go. This is probably overkill, but I always tradeoff probability against consequences. In this case, the probability of a release without the tug test is low but the consequences of an unhitching could be disastrous. Also, I’ve checked the RV brakes and the hitch at the same time.
2021 Solitude 380FL-R
Ram 3500 MegaCab SB DRW
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05-20-2023, 10:46 AM #7
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05-20-2023, 11:23 AM #8
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@Hoopy Frood and @Gronk1 nailed it. Ours works the same way and I use the same process as @Gronk1. When the second front jack is lifted about and inch off the ground I stop retracting and extend (lower) the front jacks. his will lower the first (fully retracted) jack without effecting the second jack ( the one about an inch off the ground). Stop when the first jack is an inch (or whatever height you are comfortable with) off the ground.
As side note: I always do a tug test when I hook up as this not only tests that the hitch jaws are locked, for me it also confirms that the brakes (not just the brake lights) are hooked up and working.
ChrisChris & Karen
Fort Collins, CO
2017 F-350 SRW 6.7 Lariat Value CC LB 4x4
2018 Solitude 310GK - Sold 7/2023
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05-20-2023, 10:03 PM #9
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2022 Solitude 378-MBS-R, 8k axles and disc brake package, slide toppers, dual panes, 5.5kw Onan, W/D, 3rd AC/heat pump
2023 F350 Lariat DRW on order, (canceled)
2023 Chevy 3500 LTZ long bed Duramax, 12250 GVWR, 3867 cargo cap, Z71, 5th wheel prep
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05-21-2023, 06:32 AM #10
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- Central FL
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Just add a little resistance to the one that is raising early, step on it or hold it with a fire poker while hitting the raise button. Once the slower one is up a few inches release the one you are holding and let it raise a few inches and you should be fine to do the tug test.
2022 Reflection150 226RK
2022 F150 Powerboost hybrid with 3.5L Ecoboost
Re-pack bearings necessary?
Today, 09:29 PM in Axles, Brakes, and Suspension