0
0
with Jim Mazzola
TSV Replacement Pinion Mount
Youre out wheeling in your favorite trail. Youve got yourself wedged down against a rock, you grab reverse, let the clutch out and BANG, you hear that dreaded sound from down in front. If your vehicles a Sammy you cringe and write it off as just another birfield! If however, your driving a Tracker, Sidekick or Vitara, youve got a whole new experience ahead of you. Youve either broken an axle, or most likely you have broken the rear pinion mount off the 3rd member housing. The solution has typically been to pull the housing out and go get another 3rd member. You might be able to trade a Sammy owner if he’s swapped in a set of Tracker, Sidekick, or Vitara front 3rd members. A leaf or coil sprung Sammy doesn’t utilize the pinion mount on the 3rd member. Aside from that, youre off to the junkyard scrounging for a used 3rd member. I am not aware of a solution for this dilemma, and as an owner of three of these trophys I decided to do something about it.
The root cause is this: When driving forward, the load on the pinion end is downward. The load through the aluminum boss on the side of the housing is in compression on top. When the vehicle is thrown into reverse this load reverses. The pinion wants to rise up. This rising up puts the top of the aluminum boss in tension. If you look at the boss carefully youll see that it is thinner on the top than on the bottom. Hence, the crack begins there. If you continue to stay on the gas the carnage wont end until youve got a hole in the front diff large enough to stick your fist through. Failing to exercising restraint when you hear that ominous noise down in front will cost you. Ive sketched up about 9 variations of this design. Each one having its benefits and drawbacks. The following is what I think are the best two solutions for the problem. The first one, a complete replacement mount for the 3rd member. The second is a brace for your pinion end if your fortunate enough to not have it let go yet. 
The first step is to remove whats left of the mount on the 3rd member. Grind it down till you have it close to the housing diameter. I have been able to determine that there are at least 2 different diameters of castings in the outer pinion bearing area. One is 83.5 mm and the other is 86.0 mm. 
The design is basically a horse collar, split in two. To isolate the collar from the pinion I use thin layers of rubber. I wrap the pinion with enough layers to bring the diameter up to about 95.0 mm. The horse collar utilizes the factory pinion mount and provides an additional mount on the other side of the pinion. The two pieces sandwich the pinion and provide a 360* mount to hold the pinion from both sides to keep it from twisting and shearing off the mount. 
The second solution is a reinforcement for a mount that is not yet broken. It basically uses the top piece from the horse collar and uses a layer of rubber on top only. The mount wraps over the top of the pinion and attaches in the same fashion on the other side with a rubber isolator. The most difficult part of the installation is the hole needed on the frame crossover. Its located up inside the A-arm cavity at the rear. Its difficult to get a drill in there. While I believe that these solutions will remedy a broken mount and prevent failure of one not yet broken, I do feel that the aluminum housing and 3rd member in the front axle is a bit of an Achilles heel in this vehicle. Personally I have yet to fail a front gear set or ‘corn cobbed’ a pinion gear. I do know of many folks who have though. Suzuki has available an iron housing and 3rd member that will bolt in. An upgrade ‘with beef’ here may very well be a rear 3rd member narrowed and modified to be a front diff housing. I’ve had a rear housing on the table for a 18 months now debating the issue with myself. The only problem here will be that you invariably chase the weak link to another component in the drive line. I think the axles would be the next weakest link. The question you have to ask yourself is, what spare part do I want to carry with me on the trail.
Until the next broken part…….. Jim Mazzola – KB8YMF
08/11/10 15:26
