Auto Service World
Feature   January 1, 2000   by Auto Service World

Market Feature: Transmission Trouble?

When you see how deceptive the signs can be, you'll understand how important training is.


Virtually every car owner dreads hearing that there is trouble with their automatic transmission. That is why proper service, including fluid and filter change, is becoming a stronger market for the aftermarket. Beyond preventative maintenance, however, technicians also need to understand the deeper maintenance issues at hand. Photo: Jiffy Lube.

Only two things are guaranteed in the transmission service business: automatic transmissions are going to become a larger part of the overall aftermarket service; and it’s going to get tougher to repair them. It’s not so much that automatic transmissions are becoming more difficult to repair though; they remain largely the same electro-hydraulic based systems that they have been for decades. But determining what is actually wrong with them, and even if they are to blame at all, is becoming increasingly problematic even for experienced technicians.

If ever there were a prime area to improve the technical know-how of yourself and the technicians you serve, this is it. Here are some cases in point which should direct you to seek out technical training for your customers so that they can be effective in conducting repairs.

Chevrolet Cavaliers aren’t particularly prone to transmission difficulties–particularly the three speed equipped models, despite their low cost and high production numbers–but they’re not immune to the type of failure that a standard repair garage can handle, if they can read the problem. In one case, a 1995 model with a 2.2 L engine arrived at a garage with what read like an ignition failure.

The customer complained of a severe miss under load, especially when going uphill under heavy throttle. This problem seemed to occur around 2500-3900 rpm and disappeared in 10-12 seconds.

Despite the fact that no trouble codes were being set, the dutiful technician proceeded to replace a laundry list of ignition components: crank sensor, ECM, spark plugs, ignition wires, as well as performing a solid by-the-book diagnostic of the ignition and fuel system. This included a check of the injector pulse width, fuel trim numbers, etc. The technician also looked to the CPS and the ECM, but to no avail.

The technician could and should have saved himself a lot of trouble if he had done one thing first: talk to the customer.

It turns out that the vehicle had previously been to a shop and had the torque converter clutch (TCC) solenoid replaced, but not until a problem had persisted for some time.

The technician then figured that the torque converter clutches were probably already fried. Smart thinking considering the transmission fluid had a telltale burnt smell and there was the added evidence that the “miss” occurred at specific rpm. The technician surmised that the transmission was trying to lock up until the rpm exceeded the locking action. The technician ultimately sent the customer away to a transmission shop for a new torque converter.

Like most technicians, experience counts for a lot. Unfortunately, it can sometimes lead them down the wrong path when a problem appears to be something familiar but originates somewhere else entirely. If there is any lesson to be gained in this example, it is that a more thorough interrogation of the customer and the car–checking that tranny fluid would have taken seconds–can prove valuable even when the technician thinks he’s in familiar territory.

Experience, even with transmissions, is no guarantee of success.

A technician specializing in transmission repair recently came across a completely grenaded transmission on a Ford Taurus. The AXOD-E transmission in question had chewed up its insides and so the technician overhauled all the clutches and seals, valve body, installed new solenoids and cleaned everything thoroughly. The converter was new, the cooler was flushed and proper service seemed to ensure a good result. Upon reassembly and driving test, however, the transmission exhibited a “flare-up” shift from second to third when under light load. Under heavy load, the shift seemed fine. A double check revealed no debris in the system.

The problem, as it turned out, was a low/intermediate band pin that measured 0.004″ too short, and was probably bent, but too slightly to be visible to the naked eye.

The message here, if there could be said to be one, is that when a transmission has had such severe damage, you’re best off to check everything. Perhaps another message is that even the experts have trouble with the increasing number of tiny components populating modern automatic transmissions, so if your customers don’t feel entirely confident around them, that’s okay; they’re in good company.

Sometimes all it takes is a little bit of faith. After all, what should one of your customers do if everything seems fine, but there’s no denying that something is wrong?

In just such a case, a technician found a vehicle which surged at moderate to highway speeds when the torque converter clutch engaged. Equipped with the GM TH125 transmission, the vehicle had been to shops before, with a number of attempted fixes including flushing the system, recently replaced wires, module and two, count ’em, TCC solenoids.

Despite the evidence of a problem, no codes were set. With little more than faith to go on, the technician decided that it was probably the torque converter itself at fault. In a case like this, with a relatively pricey job for the customer, a technician certainly wants to get it right. Sometimes, however, they just have to hold their breath and hope.

You can almost hear them saying it: “Your transmission needs a new torque converter” (I think).

It turns out he was correct. Despite the other work that had been performed, no one had gone as far as to replace the hard stuff. With a new converter, the transmission shifted as smooth as silk and ran as fine as Archie and Edith Bunker’s old LaSalle.

Clutch Service Do’s and Don’ts Worth Remembering

Proper repair procedures are as important in clutch service as in the more technically sophisticated automatic transmission service.

Nevertheless, there are a few items that can be taken care of to ensure that clutch service is satisfactory and that the job doesn’t come back to your customer–and your counter in turn–because some critical points were not addressed.

Flywheel Integrity

A flywheel must always be checked for flatness and finish. It is increasingly recommended that the flywheel be resurfaced whenever a clutch is replaced. It is also critical to ensure that the surface of the flywheel is not contaminated with oil or other fluids from leaking seals or other sources.

Pilot Bearing and Seal Condition

The pilot bearing/bushing keeps the transmission shaft located properly and prevents axial motion (wobble). A poor-condition bearing will not only compromise the noise from the transmission and the life of the clutch due to excessive vibration; it will also shorten the life of the seal and possibly allow transmission fluid to contaminate the clutch assembly. It is considered good practice to replace these seals as a matter of course, as it isn’t reasonable to expect them to outlive several clutches.

Transmission Shaft Condition

The transmission shaft should be in good condition and free of severe scoring. Also, the splines must in good condition, though some wear is normal. Particular attention should be paid to the pilot bearing support collar, critical to smooth clutch function.

Release Bearings

While it is common for clutch sets to include release bearings, it is somewhat less common for technicians to actually use them. This is wrongheaded and is a warranty-critical issue. New release bearings should be employed whenever recommended. The release bearing should also slide smoothly.

Lubrication

Lubrication of certain parts, such as the pilot bearing, spline shaft, bearing support collar and ball stud, should only be done lightly and with high temperature grease. Bushings should only be lubricated with a light coating of 30 weight motor oil on the friction surface. Grease on bushings actually
increases the friction and will promote noise, galling and premature failure. Too much lubricant on any surface could contaminate the clutch face and flywheel surface, so great care must be taken in ensuring no greasy or oily surface remains.

Cleanliness

As mentioned, any foreign substance can contaminate the clutch and flywheel surfaces. Cutting fluid or oil could remain on the flywheel following resurfacing and the pressure plate may have a rust preventative oil-based coating. Both surfaces should be cleaned with a good quality solvent, such as a brake cleaner.

Also, technicians should be reminded that they could be a source of contamination also, and should make sure their hands are free of grease and oil before installing the clutch.


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