If you own a fullsize truck from the 1990s, then you might very well feel the pain of more than one or two tranny swaps. All too often transmissions from this era came apart faster than most owners expected. Some light-footers got away with 100,000 miles or more out of their transmissions, but the great majority of us were breaking things well before that. So what’s a guy to doespecially one like myself who is replacing lucky number seven with transmission number eight?
Well, for starters, make friends with your local transmission guy. Next learn why your transmission breaks. Heat is almost always a factor, but certain parts can fail faster than others. Find your transmission’s weak points.
Next, find what you can do to prevent the problem(s). For every transmission out there, increased cooling capacity and heat barrier protection are excellent preventative measures. But you can also increase strength using different internal parts or internal parts made of high-quality metals.
No matter how well you build your transmission, remember that there is no such thing as indestructible. The best you can do is destruction-resistant. Depending on how much you want to spend, you can have yourself a transmission built to take thousands upon thousands of whatever type of miles you want to throw at it.
This episode of what breaks and how to fix it is for the Dodge guys this time. Those of you who own trucks that came with 518, 46RH, or 46RE transmissions know the pain that can be felt only by a ’90s truck owner. But there is hope. These overdrive transmissions are basically evolutionary versions of the venerable 727 Torqeflite. And therefore they have potential. We headed to Orange County Transmissions in Santa Ana, California, to find out what causes the failures, what breaks, and what you can do to keep your transmission alive longer.
Common Tranny Kills
If you’re having some transmission issues, the chances are that you noticed some type of indicator as soon as it started, whether it was a burning smell, slipping, abrupt shifts, or a lack of shifts.
If you experience any of these things, take immediate action. Many times it’s not too late to save your transmission.
This has to be the No. 1 killer of all transmissions. Heat can ultimately destroy even the best built transmissions, and we have the burned out clutches to prove it. Adding extra coolers can definitely help, but you don’t want to add too many and restrict the transmission fluid flow.
Unwanted heat can come from external sources as well. If your exhaust pipes run too closely to the transmission or its torque converter, the exhaust can heat up your transmission and lead to eventual tranny failure.
Particulates Clogging Fluid Flow
If your transmission overheats, is old, or is starting to deteriorate for any reason, then there’s a good chance that you have particulates in your fluid, clogging up the valve body or the fluid lines. The best prevention is to change the fluid and the transmission filter regularly. If you drop the (tranny) pan for some reason and find particulates, make sure to get a new filter, flush as much of the fluid as you can, and either clean out or replace the cooler(s).
Too Much Force
Transmissions sometimes break simply due to being overpowered by the engine. If you have a modified engine, then you might possibly be producing too much power for your tranny. Long-term damage can be worn-out clutches, but they can also suffer instantaneous input shaft, intermediate shaft, and/or output shaft failures.
Input shafts, intermediate shafts, and output shafts can all be broken in a transmission with too much force. The broken shaft you’re looking at here is the intermediate shaft out of our Dodge project truck. Notice that this shaft has had its lube holes enlarged to feed more oil to the overdrive gearset. While this can be good, it also has the potential for creating a weak point in the shaft if you’re running extremely high horsepower numbers. Stock shafts usually do not break until you start getting into the 350hp range.
You can order these shafts in 4130 chromoly or in 300M, but they are very expensive. There are also some billet drums available to further strengthen your pack.
Low Roller Clutches
The low roller clutches in the rear end of the transmission case are splined and pressed into the back of the case. And unfortunately they can sometimes spin. If this happens, you’ll either need to get a new case or use a retrofit bolt-in low roller clutch (which is a readily available and often-used item). Obviously the bolt-in retrofit is the easiest way to go.
The overdrive gearset with its overdrive clutches and planetary can sometimes fail due to a lack of lube. The best way to prevent it is to enlarge the lube circuit to allow more fluid to flow to it.