Recommended Longest Extended Pin Box for a Lippert 1621 Bolt Pattern

Updated 10/15/2025 | Published 08/20/2025

Products Featured in This Question

Lippert 1716 5th Wheel Pin Box - 15,500 lbs

(78)

$579.77

Lippert 1621 5th Wheel Pin Box - 15,500 lbs

(78)

$615.27

Curt Air Ride 5th Wheel Pin Box - Lippert 1621 & 1621HD - 21,000 lbs

(94)

$1541.87

Question:

Can I use this hitch in replacement of the Lippert 1621standard pin box rated at 15.5K? This hitch is about 3 inches longer between the kingpin and the first row of bolts. I need the additional length between the bumper of my truck and the front door of the 5th wheel. AS it is now, I cannot open my tailgate to hookup or disconnect. Thanks Regards

asked by: Mike H

Helpful Expert Reply:

Hey Mike. I have a solution for you but what your asking isn't going to work. The Lippert 1716 5th Wheel Pin Box item # LC1324791 you referenced fits a 1716 bolt pattern, which is not compatible with your trailer's 1621 pin box. The closest comparable pin box that fits a 1621 bolt pattern is the Lippert 1621 5th Wheel Pin Box item # LC1191191. It's quite a bit shorter the center of the king pin on it sits 25-5/8" from the back mounting bolts and 17-3/4" from the front ones.

The longest pin box we have that fits a 1621 bolt pattern is the Curt Air Ride 5th Wheel Pin Box item # LC158778. The center of the king pin sits 27-3/8" from the back mounting bolts and 19-1/2" from the front one.

What kind of 5th wheel trailer do you have and what kind of 5th wheel hitch are you currently using?

expert reply by: Jerred H

Jerred H.

9/12/2025

Hey Mike, did you have a chance to try out the Curt Air Ride Pin Box for your setup? I'm curious to know if it provided the extra length you needed for your truck and 5th wheel. Your experience could really help others facing the same issue.

Mike H.

9/12/2025

@JerredH I ordered it the other day and I am just waiting for it to arrive next week. I will the put it on and let you know how it worked out. Thanks for the help and follow up

Mike H.

10/15/2025

@JerredH I finally got this hitch and installed it. With this new hitch I was able to back in and lock into the 5th wheel hitch with the tailgate down. This left about 3/4 inch between the tailgate and the front of the 5th wheel, but I had to be exactly lined up and straight. There was no room for anything else. This was definitely an improvement but it was a little to tight for my liking. I then measured the exact placement of the center of the 5th wheel hitch over the center of the axle. My hitch center was 4 inches forward of the axle center. I then repositioned the hitch towards the back of the truck bed so it was only one inch forward of axle center. This now gives me just about 4 inches of room between the 5th wheel and the lowered tailgate. Plenty of room now for not only hooking up but also make a big difference in my ability to back up on a sharper angle with out having to worry about the nose of the 5th wheel hitting the truck cab. We then went for a long drive over some roads that are not know for being the smoothest. The ride was significantly improved with the new hitch and there is absolutely no notable difference in weight distribution from the front of the truck with the hitch positioned further back and there was also no difference in suspension squat on the truck. This also now allows me to not have to get out and manually allow my slider hitch to slide to and from travel and position mode to hook up or back into sites. It all turned out to be a real win, win for me. Thanks very much for the great suggestion and pointing me towards this hitchredH

Jerred H.

10/15/2025

@MikeH You're welcome! That's great to hear! Glad you were able to make those adjustments and find a more comfortable setup for towing your trailer. Let me know if you have any additional questions down the road.