TASC Force Tips
- Author: Ed Lee, Deltrans
Repair Kit Saves Cracked Case on A500 (42RE/42RH) & A518 (46RE/46RH)
There are times when even the most-routine task can turn ugly in the blink of an eye. When this happens we could all use a little help, sometimes even a small miracle.
A 1995 Jeep Grand Cherokee was brought to a Cottman Transmission shop in Jennings, Mo. The customer‘s complaints were typical for this model transmission and correct for the mileage of the vehicle. A complete transmission and converter rebuild were sold and, because of the chronic cooler-line problems, a cooler-line update was sold for added security.
Technician Andy Hanneken performed the rebuilding chore, then handed the unit off to the R&R man.
The R&R went flawlessly right up until the new cooler-line fittings were being installed. When the rear cooler-line fitting was installed into the case, there was a loud cracking sound as the case split (task turning ugly). The sound of a case breaking gives you that sick feeling in your stomach, like the one you get when the love of your life says goodbye for the last time. In fact, about the only cracking sound that is worse is the one you hear on a ski slope when it is one of your own bones breaking.
It would have been easy at this point to look back and talk about what could have been done to prevent the case from breaking. Yes, removing the factory-installed sealant from the threads (see Figure 1) with a wire wheel and installing a good liquid thread locker might have been a big help. Simply applying less tightening torque might have prevented the break, but this 20/20 hindsight was too late.
Andy contacted Cottman’s international troubleshooter, Brian Workman, and told him about the problem. (Enter small miracle.) Brian told Andy that he had heard of a prototype cooler fitting to repair cracked cases that could be installed without removing the transmission from the vehicle. This was especially good news for Andy, because not only would the costs of an additional R&R and case swap be bad enough but also replacement cases sell for a premium in his locale.
No kits for the repair fitting were available at the time: However, Brian was able to get a prototype fitting and Andy was able to piece together the other components.
Besides the fitting, one of the other key items in the kit is a tap. We were all taught that pipe threads are tapered. This fact allows them to be tightened to prevent leaks. Of course, this is also what splits the cases. The NPT (National Pipe Thread) tap cuts a tapered thread. Also available is an NPS tap that cuts a straight thread. The NPSF tap cuts a straight thread that is fuel grade. A machinist would call this a Class 3 fit.
Andy had the NPSF tap along with a bottle of 609 Loctite™ (the other key item) sent to the shop by overnight delivery, and Brian sent the repair fitting.
The original cavity was threaded well past the cracked area with the new tap (there is plenty of room to do this). The fitting was coated with 609 Loctite and screwed into the case well past the cracked area. The original fitting, which cracked the case, then was screwed into the repair fitting and the replacement lines were installed (see Figure 2). The new setup was leak free, and life was back to normal for Andy.
Don’t you love a happy ending?
The TASC Force (Technical Automotive Specialties Committee) is a group of recognized industry technical specialists, transmission rebuilders and Sonnax Industries Inc. technicians.