Remounting a Yamaha Rhino Rear Differential
Sometimes we fail to recognize the essential maintenance that needs to be done on our off-road rig until it breaks down on us. One fatal flaw we might miss in servicing the Yamaha Rhino as it ages is rear differential mounting damage.
As your Rhino ages, the rear differential mounting bolts can loosen without you noticing. This could eventually create problems like axles jumping out of the carrier or even breaking due to premature wear of the axle joint. Since there are only two mounting points on the upper portion of the differential, the bottom can swing wildly when the upper bolts become loose.
One way to see if your diff is loose it to jack the rear of the machine up with both rear wheels off the ground and gently spin one wheel forward or back while watching the rear differential. If the differential moves in the slightest then you need to tighten the bolts that hold it in place. The most common visual indicator only becomes apparent after the diff has torn away from its upper mounts. The framework will crack and eventually allow torsional twist to rip the diff right out of the frame. This is what happened to one Rhino owner’s machine and we’ll explain how we repaired it.
This rear differential has torn all of the structural steel from the main frame, most likely due to loose mounting bolts.
Yamaha Rhino Differential Repair
Starting with a complete disassembly of the rear of the machine, including the removal of the bed, exhaust, rear suspension and mid-shaft, we made room to get a clear view of our problem. This differential dissection was probably the worst we had ever witnessed and it required a total re-fabrication of the differential mounting structure, as it had ripped everything clean out of the frame.
After removing the axles and rear suspension arms, the differential fell out of the frame.
Luckily, there is an ingenious fabricator who developed a kit for such a problem. His name is Jason Baxter of Baxter Built Fabrications. This young man has a system that not only re-centered the differential for proper alignment to the engine, but he provides cross members and welds in shoulder pucks to resurrect the framework needed. The kit consists of right and left upper differential mounts, new bolts and locking nuts, as well as a metal top plate for added strength.
This rebuild kit from Baxter Built Fabrication comes complete with everything needed to rebuild the framework for the differential.
After removing the entire differential and cleaning up all of the mounting surfaces it was time to mock in our diff for placement and leveling. This is where the shoulder pucks and cross bars come into play and help you reuse as much of the original mounting locations as possible. This is a crucial step and should be looked over two or three times before the first spot-weld is made. We used a set of specific length tubing and brackets to hold the differential at the proper location for installation.
Cleaning up the original framework revealed that some factory pick points on the frame could be used as a reference.
Once all of the weld slag and paint had been removed, we could begin the mock up for the new parts.
On most differentials that get beat out of the frame this bad, the mounting bolt holes will also be worn or ovaled. The kit Baxter sells comes with slightly larger bolts and the differential mounting holes need to be cleaned out. This requires very light drilling and removes just enough material to allow the new bolts to fit in correctly. Once drilled out the process can move forward.
Drilling out the mounting holes on your differential is a must and this gives the new harder and thicker bolts a smooth and centered place to hide.
Bolting the kit parts to the rear differential and positioning it in place in the framework is the best way to get a good look at its position. This also helps eliminate most guesswork. Be sure to not tighten the diff braces to the differential too tight as this makes clearance between the braces for removal of the differential very difficult. Finger tight on the bolts will be fine.
Using the only intact frame locations we began installing the horizontal cross bars and shoulder pucks.
After getting the shoulder pucks tacked in place, we removed the differential and cross bars so we could weld these in easier. Once our mounts for the cross bars were welded, we reassembled the horizontal bars and sat the diff back in place using the height tool and spacing tubes to get a true center for the differential. This is where the remaining tack welds were made and again we removed the differential to gain clear access to the areas that had to be fully welded.
Using a dual C-Clamp we held the steel in place for the tack welds.
After laying in the front horizontal bars, we were able to drop the rear differential assembly in place and install the alignment jig.
Once the kit is welded in place you have the choice of adding the dimpled top plate to strengthen the repair even more. This part not only makes the repair extremely tough, but it also gives the mount a custom look.
Welding in tight areas can be a challenge, but once all was completely welded the framework was ready for paint.
The final step was to clean up the welds a little and sand any areas that would be getting a good coat of paint. The black rattle can covered the new steel well and it was not long before the rear suspension was going back on for a test run.
A good shallow coat of paint allowed to dry for 20 minutes, followed by two more thicker coats a few hours apart, gave the finished work a nice look.
Cleaning the metal and rubbing the steel down with acetone helps paint adhesion as well.
During the assembly we noticed the output shaft from the motor to the rear differential was very worn and decided to replace it just as a precaution. If you see any seals or even brake pads that look worn, this is a great time to replace those, too.
If you need a kit like this to get your Yamaha Rhino back on the trail, give Jason at Baxter Built Fabrications a call at 419-953-8509.