Yukon Dana 80 Steel Full Spool - 37-Spline, 4.10 & Up
YP FSD80-4-37
The Yukon Dana 80 37-Spline Steel Full Spool replaces the factory differential carrier with a solid connection between both rear axle shafts, keeping both wheels locked together at all times. Unlike an open differential or automatic locker, a full spool eliminates differential action entirely, delivering consistent traction when climbing ledges, launching hard, or putting power down on uneven terrain. It's a straightforward drivetrain setup for rock crawlers, rock bouncers, mud trucks, drag racing vehicles, and dedicated competition builds where traction and strength take priority over street manners.
Manufactured from heat-treated 8620 steel, this Yukon spool eliminates the spider gears, clutches, springs, and engagement mechanisms found in conventional differentials and lockers. Designed for Dana 80 rear axles with 37-spline shafts and 4.10-and-up gear configurations, it provides a simple, durable replacement for the factory carrier. With no internal differential mechanism to engage or disengage, the spool keeps both axle shafts mechanically connected under demanding off-road and racing conditions.
Includes:
- (1) Yukon Dana 80 37-Spline Steel Full Spool - 4.10 & Up
Important: This spool permanently locks both rear axle shafts together and is not recommended for regular street driving. Carrier bearings, ring and pinion gears, and differential installation components are not listed as included.
Specifications
| Manufacturer | Yukon Gear & Axle |
|---|---|
| Part Number | YP FSD80-4-37 |
| Product Type | Steel Full Differential Spool |
| Axle Platform | Dana Spicer 80 |
| Ring Gear Diameter | 11.25" |
| Axle Spline Count | 37-Spline |
| Carrier Break | 4.10 & Up |
| Gear Ratio Compatibility | 4.10 and Numerically Higher Gear Ratios |
| Material | Heat-Treated 8620 Steel |
| Differential Type | Full Spool / Permanently Locked |
| Traction Type | 100% Mechanical Lockup |
| Differential Action | None |
| Carrier Replacement | Yes |
| Axle Position | Rear |
| Street Use | Not Recommended |
| Installation Type | Full Differential Carrier Replacement |
| Primary Application | Rock Crawling, Rock Bouncing, Mud Racing & Competition Off-Road |
| Quantity | Sold Individually |
Fitment
Designed for compatible Dana 80 rear axle assemblies using 37-spline axle shafts and 4.10 or numerically higher gear ratios. Verify the installed axle, spline count, carrier break, and ring gear configuration before ordering.
| Make | Model | Year Range | Axle Application |
|---|---|---|---|
| Universal | Custom Axle Builds / Compatible Heavy-Duty Truck Applications | Varies | Dana 80 Rear, 37-Spline, 4.10 & Up |
Fitment Notes:
- Fits compatible Dana Spicer 80 rear axle applications
- Requires 37-spline axle shafts
- Designed for 4.10 and numerically higher gear ratios
- Replaces the factory differential carrier with a full steel spool
- Not intended for 35-spline or 40-spline axle configurations
- Not recommended for regular street-driven vehicles
- Verify axle identification, spline count, carrier break, and ring gear compatibility before ordering
- Vehicle make and model alone do not establish compatibility with this spool
FAQ
What is a full spool and how does it work in a Dana 80 axle?
A full spool replaces the factory differential carrier and permanently connects both axle shafts together. Unlike an open differential or automatic locker, it has no internal differential action and forces both wheels to rotate at the same speed. This provides consistent traction for dedicated off-road and competition applications.
What is the advantage of a Dana 80 spool over a locker?
A spool is mechanically simpler because it eliminates the internal gears, clutches, springs, and engagement mechanisms found in conventional differentials and lockers. With fewer moving components, it's a durable option for dedicated race vehicles, mud trucks, and rock crawlers where full-time traction matters more than street handling.
Will this spool fit both 35-spline and 37-spline Dana 80 axles?
No. This Yukon spool is designed specifically for Dana 80 rear axles with 37-spline axle shafts. It will not accept 35-spline or 40-spline shafts. Verify the axle shaft spline count before ordering.
What gear ratios will the Yukon YP FSD80-4-37 fit?
This spool is designed for Dana 80 differentials using the 4.10-and-up carrier configuration. It supports compatible 4.10 and numerically higher ring and pinion gear sets. Verify ring gear mounting compatibility and carrier requirements before ordering.
Can I drive a Dana 80 spool on the street?
We don't recommend it. A full spool forces both rear wheels to rotate at the same speed, even when turning. On pavement, this causes tire scrub, increased drivetrain stress, and changes in handling. Spools are best suited for dedicated off-road, drag racing, and competition vehicles.
Does this spool replace the entire differential carrier?
Yes. This is a full spool that replaces the original differential carrier assembly. It is not a mini spool that installs inside an existing open differential case. Proper carrier bearing preload, ring gear backlash, and gear contact pattern must be established during installation.
Does the spool include bearings or installation hardware?
No additional installation components are listed as included. We recommend using the appropriate Dana 80 carrier bearings and differential setup components when installing the spool, especially during a complete axle rebuild or gear change.
Is a Dana 80 spool a good choice for a rock bouncer or competition buggy?
Yes. The Dana 80 platform is popular in high-load drivetrain applications because of its large ring gear, heavy-duty axle components, and available aftermarket support. Paired with the correct 37-spline shafts and gearing, this steel spool provides a straightforward, permanently locked differential setup for dedicated rock bouncers, mud trucks, and competition builds.