What This U-Bolt Fits
This is a square U-bolt, not round - meaning it's built to wrap a square axle housing or square spring seat, common on trailer suspensions and some straight truck applications. The 3/4" refers to bolt diameter, 6" is the inside width across the legs, and 8" is the leg length before the bend.
These get used to clamp the axle to the spring pack or to a torque arm bracket on trailer suspensions - Hutch, Reyco, Freuhauf-style setups and similar. Square stock axles need square U-bolts; round axle tube needs round U-bolts. Mixing them up means the bolt won't seat right and you'll never get proper clamp load.
Standard hardware, but standard doesn't mean universal. Axle width, spring seat width, and leg length all have to match your actual application or the bolt either won't clear or won't clamp down tight.
Reading the Cross-Reference Numbers
FW88-0609/453 and TM88-11 show up as cross-references because they're the same 3/4x6x8 square U-bolt spec sold under different suspension component brand names - FW and TM series numbers are common on trailer axle and torque arm parts catalogs. Same thread pitch, same leg spacing, same bend radius.
What can throw you off: axle manufacturers sometimes run slightly different inside widths for the same nominal axle size, and leg length varies depending on whether you're clamping through a thin spring seat or a thick torque arm bracket. An 8" leg that works on one application might come up short - or too long and bottom out - on another.
Surest way to confirm is to measure your old U-bolt or pull the number off the spring seat casting if there's a part tag. If the old bolt is too rusted or sheared to read, measure inside width axle-to-axle and leg length from the bend to the tip - that'll get you in the right ballpark even without a legible number.
Ordering From PartStop
We keep square U-bolts in stock at the Tacoma counter in common trailer and truck sizes, this 3/4x6x8 being one of the more frequent calls. Grade 5 or better steel, standard 6+ month warranty against defects.
If you're local, same-day pickup works fine if you call ahead to confirm we've got your exact size on the shelf - square U-bolts aren't one-size-fits-all and we'd rather check than have you drive out for nothing. Ship nationwide too, and freight's usually just a couple days for hardware like this.
At $29 for a heavy-duty square U-bolt, it's not the kind of part worth stretching your budget by guessing on size - measure twice, order once, save yourself the return shipping.
UBOLTSQUARE Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to UBOLTSQUARE. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| Cross-Reference | FW88-0609/453, TM88-11 |
Frequently asked questions
Does UBOLTSQUARE fit my trailer axle?
Depends on your axle width and spring seat thickness - this is a 3/4" diameter, 6" inside width, 8" leg length square U-bolt. Pull your old bolt or measure the axle housing width and leg length before ordering, since trailer axle specs vary by manufacturer even within the same nominal size.
Is this the same as the FW88-0609/453 U-bolt?
Same spec - 3/4x6x8 square U-bolt, same thread and leg dimensions. It's a common size that gets sold under different catalog numbers depending on the suspension brand, but the physical bolt is interchangeable as long as your application calls for that exact size.
Can I use a square U-bolt in place of a round one if my axle is round tube?
No - square U-bolts are bent to wrap flat/square stock and won't seat properly against round axle tube. You'll get uneven clamp load and risk the bolt working loose. Check your axle housing shape before ordering.
Not sure it fits? We check before you pay.
Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.