GPM Racing 4140 Carbon Steel + 7075 Alloy Rear Complete Diffs & Upper Bulkhead & Diffs Housing for Traxxas 1/6 4WD XRT 8S-78086-4 (XRT13KIT)

Product summary and purpose

This aftermarket drivetrain kit is supplied for TRAXXAS large-scale trucks and identified by the model XRT13KIT from GPM. It groups the rear differential, differential housing and upper bulkhead to provide increased robustness for 1/5-1/6 scale off-road vehicles subjected to heavy loads and repeated impacts.

Materials noted in the source include 4140 carbon steel for the differential gears with heat treatment for torsional strength and wear resistance, and CNC-machined 7075-T6 aluminium for the differential housing and upper bulkhead to maintain stiffness while controlling weight. The bevel gear is shown as 32T with a 10T pinion and module M1.6, useful when selecting spare gears or scheduling maintenance.

Installation guidance: the assembly is designed to replace factory rear diffs and related housings on compatible chassis. When servicing, verify bearing sizes and gasket placement from the parts list and confirm gear mesh and preload after changing lubricants or bearings to ensure reliable engagement under heavy use.

Compatible Models

• TRAXXAS 1/5 X-Maxx 8S Monster Truck-77086-4
• TRAXXAS 1/6 4WD XRT 8S-78086-4
• TRAXXAS 1/5 X-Maxx 8S Ultimate-77097-4
• TRAXXAS 1/5 X-Maxx 8S Monster Truck-77096-4
• TRAXXAS 1/6 XRT Ultimate 8S-78097-4
• TRAXXAS 1/5 X-Monster BIGFOOT 50th-77136-4
• TRAXXAS 1/5 X-Monster Chassis Monster Truck-77036-4

The GPM XRT13KIT serves as a heavy-duty aftermarket replacement aimed at extending drivetrain life and providing predictable behavior for TRAXXAS large-scale trucks under demanding off-road conditions.

What is supplied with the XRT13KIT assembly?

The assembly package includes the rear differential unit, the differential housing and the upper bulkhead, together with the bearings, gaskets and pinion documented in the original listing.

What alloys and steels are specified?

Gears are 4140 carbon steel with heat treatment, while housings and the upper bulkhead are CNC-machined from 7075-T6 aluminium for strength and stiffness.

Is the kit compatible with all XRT and X-Maxx variants?

Review the Compatible Models list above; the kit is intended for the TRAXXAS variants specified and functions as a direct replacement for the factory rear diff and bulkhead assemblies on those chassis.

Any final installation advice?

Confirm bearing fit and gasket seating, set gear mesh accurately, torque fasteners to factory values and perform a light break-in to verify stable operation. Write Product Review Please sign in your account before you can write any review. Sign In Close

Made to order: GPM Racing parts are shipped to us from GPM’s factory, so please allow around 14 days for dispatch.