Bonus Tech
- Author: Dan Currier
- Subject Matter: 2006-08 Hummer H3
- Issues: Grinding noise with neutral-out
There have been numerous instances recently of 2006-08 Hummer H3 vehicles arriving on a flatbed, with a stated customer concern of a grinding noise accompanied by a neutral-out while driving down the road. By the time the tow-truck driver drops it at the shop and we begin diagnosis by attempting to duplicate the concern, the “ghost” is gone and the vehicle drives perfectly!
The prospect of any intermittent diagnosis is discouraging, but we forged ahead and racked the vehicle for an initial inspection. There were no obvious signs of driveline distress, but a bulletin search turned up a promising prospect. TSB 08-04-21-005A mentions a condition in which the plastic mode fork in the transfer case could melt, causing the transfer case to be in a partially applied position. Upon cracking open the transfer case, we found the fork was indeed badly worn, so we rebuilt the case and included an updated fork. With the absence of any other evidence, the vehicle was released to the owner.
One week later, it came back on a flatbed with the same neutral and grinding concern. And again, once off the tow truck it drove just fine! Back up in the air it goes for another in-depth driveline inspection, but this time we struck solid gold. During a check of the front axles, the passenger side popped right out under light prying, as if the retaining clip was not there. Removing the axle completely, we could now see the evidence of failure. The spline end of the axle was ground up as a result of walking its way out while driving down the road (Figure 1). This disengaged the differential from the wheel, resulting in the neutral condition.
Why would this create a neutral condition?
With this particular transfer case, all four wheels must be engaged to move the vehicle unless it is placed in 4HI lock. Also, as for most 4×4 systems, all tires must be within ¼-inch circumference of one another to prevent binding of the driveline. On the vehicles we’ve seen with this issue, the tires were not in the best shape, so the owners were counseled to replace the tires after we installed a new axle.
We’ve seen this a few times now, and the next time a Hummer H3 comes our way with this concern, we know exactly where to find the ghost in this machine.
Dan Currier has been working in the transmission industry for over 15 years, now at Jim and Sons Transmission Specialist in Cuyahoga Falls, Ohio. Currier, one of the sons of the company’s third generation to our company, focuses on diagnostic and electrical repairs on 4×4 and transmission control systems. His work includes R&R, converter rebuilding and building more than 1,000 transmissions, from 4L60-E’s to ZF series.
