By TRT Road Service
Check a short list before you couple again: the release handle position, the parking brake on an air-release unit, and whether the jaws are open. These checks come from the maker’s own prep steps, not a repair. If they do not clear it, stop and call TRT Road Service at (928) 577-1496. We are open 24/7 and we come to you. Do not drive a trailer you cannot confirm is locked.
What the maker's prep steps check
These checks come from SAF-Holland’s steps for preparing a fifth wheel for coupling, published by Fleet Equipment Magazine. The steps also say to follow your own fifth wheel maker’s instructions. Your model may differ. This list is a pre-coupling prep list. It is not a fix for a stuck release on a coupled trailer.
Set up the area
SAF-Holland’s steps say the coupling area should be “flat, level and clear of persons and obstacles.” If you are on a slope or a soft shoulder, do not work on the coupling. Call.
Check that the locks are open
For a manual release, SAF-Holland says to pull the secondary release handle, hook it on the casting, then pull the handle completely out. Then look at the throat. The locks should be completely open and ready to accept the kingpin.
Check the release handle position
If the locks are not fully open, SAF-Holland says to check that the release handle is in the extended “open” position. On the Holland FW35 model, the same guide also says to check the shaft adjustment nut and washer. They should be away from the front of the wheel.
Check the air release, if you have one
For an air-release unit, SAF-Holland says to set the tractor parking brake and pull the release valve until the mechanism opens and locks in place. Then release the valve and release the parking brake.
One SAF-Holland product works the same way on the parking brake. SAF-Holland’s announcement of HOLLAND SmartSTO says that system will not operate unless the tractor parking brake is set. If you have a different unit, read its manual.
On air-release units, SAF-Holland’s steps say to set the tractor parking brake before pulling the release valve. Source
What to leave alone
The sources we read give no step for prying, hammering or cutting a fifth wheel. We will not invent one. If the release does not work after the checks above, stop there.
Leave these alone. This is our advice, not a rule from the sources:
- Anything under the trailer while it is loaded or can move. The SmartSTO announcement describes its release as a way to avoid reaching under the trailer.
- Any part you have to force to move.
- Any fix that is not in your fifth wheel maker’s manual.
Why you should not drive on a lock you cannot confirm
Federal rules cover the locking mechanism. 49 CFR 393.70 says “Every fifth wheel assembly must have a locking mechanism.” That mechanism must prevent the halves from separating unless “a positive manual release is activated.” A readily separable fifth wheel must lock automatically on coupling.
A second rule covers the driver. 49 CFR 392.7 says no commercial motor vehicle shall be driven unless the driver is satisfied that the coupling devices are in good working order.
This is our reading of that rule. If you cannot tell that the jaws have closed on the kingpin, you have no basis to be satisfied. Do not drive.
“Every fifth wheel assembly must have a locking mechanism.” Source
No commercial motor vehicle shall be driven unless the driver is satisfied that the coupling devices are in good working order. Source
When to stop and call
Stop and call if any of these is true:
- The locks will not open after the handle and air-release checks.
- The jaws do not appear to close on the kingpin after you couple.
- The release handle does not return to its normal position.
- You are on a grade, a shoulder or soft ground.
- You are not sure what you are looking at.
You do not need to prove the problem is serious before you call. A coupling you cannot trust is the reason to call.
How TRT handles a fifth wheel call
TRT Road Service is a mobile diesel repair and heavy-duty diagnostics business. Fifth wheel work is part of what we do. Our mechanics come to your breakdown location. There is no shop drop-off. You can read more about mobile diesel repair for trucks on our site.
The owner, Tennessee, personally handles most jobs. We serve drivers on I-40 from Seligman through Kingman and Needles to Barstow. We also serve AZ-95 and US-95 from Searchlight to Parker. When you call, tell us three things: where you are, what the handle or lock does, and whether the trailer is loaded.
TRT’s mechanics come to your breakdown location. No shop drop-off.
Frequently Asked Questions
Quick answers to the questions people ask before they call or book.
Can I tow with a fifth wheel I think is locked?
Only if you are satisfied it is locked. Federal rule 392.7 puts that decision on the driver. If the jaws are not visibly closed around the kingpin, we advise you not to drive. Call instead.
Why does my air-release fifth wheel do nothing when I pull the valve?
Check the tractor parking brake first. SAF-Holland’s steps for an air-release unit start with setting it. For HOLLAND SmartSTO, the maker says it will not operate unless the parking brake is set.
Can the jaws look closed and still couple?
SAF-Holland’s steps say two things must hold. The release handle must be extended. On the FW35, the adjustment nut and washer must be away from the front of the wheel. Then the kingpin entering the jaws can open them. If either is not met, repeat the open-lock checks.
Do you work on a fifth wheel at the roadside?
Yes. TRT is mobile only. We come to the truck, wherever you are stopped in our service area.
Call before you try anything else
Fifth wheel trouble costs you time, and a bad guess can cost more.
Call TRT Road Service
If the checks above do not clear it, call TRT Road Service at (928) 577-1496. We are open 24/7. You can also use the contact page to send details. We do not promise an arrival time.
TRT Road Service
