Up to Standards

• Subject: Adding new driveline services requires knowledge and preparation
• Essential Reading: Rebuilder, Shop Owner, Center Manager, Diagnostician
• Author: Mike Weinberg, Rockland Standard Gear, Contributing Editor

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In the past decade we have seen tremendous change in our lifestyles and in our industry. The factories that produce the automobiles we work on have raised their quality immensely. As a consumer, this is a wonderful thing, for we all have endless choices in buying a quality product.

The downside for us as professionals in transmission repair is that these cars and the components that create the vehicle do not break or wear out as often. The cost of repairs is higher because of more-complex driveline systems, and the vehicle manufacturers are supporting their dealer networks with longer warranty periods. The ill-conceived “Cash for Clunkers” program has removed about 700,000 vehicles from the road that we will never have a chance to work on. The current economic mess has left many people in survival mode, just trying not to go broke, and this does not help us in finding more customers to sell repairs to.

The lines between dedicated transmission-repair shops and general-repair facilities have become blurred, as trans shops are now doing more general-repair work than in previous times to help cover their overhead and the general-repair shop is now swapping transmissions and other components available through aftermarket rebuilders for the same reasons. It seems that nobody wants to turn away any work that will bring in more cash. This is a natural transition to the change in the repair business that is ongoing but also creates some new problems for suppliers and repair shops.

One of the largest of these issues is the temptation by many businesses to take on jobs they are unprepared or unqualified to do successfully. The lack of expertise and skill creates a climate for failure. There is nothing wrong with going into new markets and trying to expand business, but there needs to be careful thought, planning and a complete understanding of the technical issues involved.

It seems that we are speaking with people on the tech lines on a daily basis who seem to have no understanding of the job they are trying to do. For instance, a tire store ordered a differential carrier for a pickup truck. The technician did not know the difference between an open carrier and a limited-slip carrier. It would seem very unlikely that this technician would be able to complete this repair successfully with such limited knowledge, but he was going to try anyway.

I have nothing against a man trying, but “chance favors the prepared mind.” It is critical that anyone who is new to something should make an effort at understanding the basics involved and get into the theory of operations for the component being worked on.

Questions that are now being asked frequently by unprepared individuals and shops are related here with the basic answers in an attempt to help with understanding how driveline systems work.

Complaint: The trans grinds in all gears.

Question to the installer: Is the clutch releasing properly? If a transmission is grinding in all gears, the first place to look would be the clutch system, as it is doubtful that all the synchronizers have failed at once. We need to have about a 0.050-inch air gap between the disc and the flywheel/pressure plate with a proper clutch release. The problem can be a poorly adjusted clutch, a failed clutch, a hydraulic system that is not working properly or contains air, a bent or rusted disc, a seized pilot bearing, or a flexing firewall or pedal issue. Work from the outside in, meaning always do the least-labor-intensive things first and disassemble the transmission last. If the input shaft is still engaged to the engine and is turning at engine speed without slowing, the synchronizers do not have the frictional capacity to slow or speed up the gear and the engine, and grinding shifts will occur.

Complaint: The transmission is hard to shift and, it’s worse when cold. All shifts are notchy and high-effort.

Question to the installer: What type of oil did you put in the unit? In every transmission design the oil is specified to work with the synchronizers and is very specific. The oil needs to be of a viscosity that matches the rate at which the synchronizer ring can exhaust the oil from the cone of the speed gear and will work with the material from which the ring is made. This is a simple issue to resolve before you fill the transmission with anything that is lying around the shop just to get the job out the door. After a transmission is filled with an incorrect lube it may take considerable driven miles with the correct fluid for the rings to begin to work correctly. Look up and use the correct lube fill to eliminate these problems.

Complaint: The transmission is jumping out of gear.

Question to the installer: If it is jumping out of gear why are you ordering synchro rings? Gear jump-out is a function of excess endplay on the mainshaft or countershaft, depending on design; excess endplay on the speed gear itself; or worn-out back taper on the speed-gear engagement teeth and/or the synchronizer sliding sleeve. It also can be caused by items external to the transmission, such as shift cables, misadjusted shifter, worn-out shift forks, or some wear or damage to the actual stick, where the sliding sleeve cannot make full engagement to the speed gear.

It will never be due to the synchronizer ring, as the ring is responsible only for slowing or speeding up the speed gear until the shaft speeds equalize and the sleeve can engage the gear completely without clash. The engagement teeth on the speed gear and sliding sleeve are cut at an angle, which is called back taper and acts as a torque-locking device to hold the gear and sleeve in proper position with changing throttle positions. Look at the sides of the engagement teeth and make sure they are not shiny and relieved, indicating that the back taper is worn out.

Complaint: Grinding going into one or more gears; all synchro rings replaced with new.

Question to the installer: Did you check the ring- to speed-gear-cone fit to make sure the cone of the gear is not undersized? The cones on the speed gears to which the synchro ring engages are tapered. You can twist the ring onto the cone and check the clearance between the lower edge of the ring and the face of the gear with a feeler-gauge set. However, this is unreliable, as you really have no way of measuring the cone for a worn-out taper. A quick way to do this is to clean the cone with solvent and dry it thoroughly. Take a permanent black felt-tip marker and paint up the cone. Then twist a known-good ring on it until it bottoms, remove the ring and check the pattern it leaves. You may find that it leaves only a slight pattern on the very bottom or top of the cone, which means that the taper is worn and the gear needs to be replaced.

Complaint: Multiple types of failures and complaints involving transfer cases, front-wheel-drive transmissions and differentials.

Question to installer: Have you measured the tire sizes and pressures? The word “measure” here is critical, as reading the sidewall markings is no help. This is a basic step in any diagnosis. Measure the tires individually by a tape measure around the center of the tread, or with a stagger gauge, to make sure all tires’ circumferences are within a maximum of 1/4 inch. Pressures must be the same also. A mismatched set of tires will cause any number of transfer-case malfunctions or codes and will overheat and damage the rear end on any differential. The reason is that any transfer case controlled by a computer or a viscous coupling will interpret the difference in tire circumference as a slip and send power to all for wheels continuously. The reasons that differentials fail in transaxles because of mismatched tires is that the side gears of the differential are supposed to work only when the vehicle is in a turn. If the tire sizes are unequal, the difference in the rolling radius of the tires causes the side gears to work even in a straight line, and the differential overheats and fails.

Complaint: Recently installed ring-and-pinion set fails at very low mileage.

Question to the installer: Was the new ring and pinion heat-cycled? The proper setup to the ring and pinion for backlash and pinion depth is, of course, critical for proper operation and durability. This is not the last step in the repair. After the differential is filled with fluid and the test drive is about to be undertaken, there is a proper break-in procedure for the new ring and pinion to make sure they lap together properly for long-term durability.

Take a slow road test for about 15 minutes and bring the vehicle back and park it for about a half hour. Go on a second road test at medium speeds for 15 minutes and return and park the vehicle for a half hour. Take a third road test for 15 minutes at highway speeds and return and park. Check for leaks and call the customer. Heat-cycling the gears this way ensures long-term durability, as they learn to mesh with each other at operating temperatures.

The old saying “look before you leap” applies in everything you do. Just because an opportunity presents itself as more cash flow, think before you jump in with both feet. If you wish to expand your business and try to keep all profit opportunities in house, do some research as to what you can accomplish successfully. Look at the repair manuals, look at various alternatives available in the aftermarket, look at the tools you will need. If you need help, ask your supplier to explain the issues to you. If they can’t or won’t help you find a supplier who will.

Every job has a learning curve, and everything is harder than it looks, especially the first time. Make the investment in yourself to learn, as we all walked before we ran. If you don’t know the difference between an open differential and a limited-slip, you are not going to do your customer or yourself any favors doing this differential repair.