American Crane & TRactor Parts Blog

Power Train – FAQ


Here at American Crane & Tractor Parts we pride ourselves on having an extensive knowledge of all things power train. We have 4 experienced mechanics that have a whopping 85 years of combined experience. We’ve had them gather up some of the most frequently asked questions they hear about power train.

How can I check my carrier for cracks?

– Inspect your carrier for cracks by placing it in a parts washer at a temperature of 120 degrees or higher. Blow

all the water off of it and spray penetrate oil on the part, then, let it set for five minutes, re-wash the part, and you will see the oil outline if a crack is present.

How can I ensure a long life for my differential gear?

– Make sure the back lash is properly set between the pinion gear and the ring gear; if it’s not you will end up cutting the life of the gear in half.

How can I extend the life of my final drive hub?

– Torque and then weld the nuts that are holding your sprockets to the hub.

Any tips on installing a cup and cone?

– For proper and easy installation of the bearing cup lower the temperature by placing the cup in a freezer. To install the cone bearing raise the temperature by placing it in hot oil, never use a torch to raise the temperature.

What about removing a cup and cone?

– A fast way to remove a cone from your part is to cut the cage around the rollers and heat the inner race, it will slide right off. An easy way to remove a bearing cup from a part is to weld a small bead around the center of the cup and it will fall right out.

Why is my bearing failing?

– There are numerous reasons why your bearing could be failing and it’s not always easy to determine the exact cause behind it. However, the number one reason for bearing failure is contamination. It’s estimated that 90% of failures are because of particle contamination. Poor lubrication is the next most common issue.

What is making my transmission hot?

– Quite a few things could be making your transmission hot. It could low oil level, a high oil level, your transmission cooler might not be completely open, low oil flow due to pump water, too much resistance between the plates and discs, or even long periods of the converter at or near stall speed.

Why is my torque converter getting hot?

– Could be because of torque failure, your oil cooler not being completely open, too much oil leakage in torque converter at or near stall speed, oil pump failure, or it could even be because your inlet relief valve is not operating correctly.

How can I maximize my bearing life and prevent it from failing?

– To maximize bearing life it’s important to eliminate the four primary causes of premature failure — improper installation, improper tolerances, contaminated lube oil, and overload (fatigue).

How do I know if I can reuse a clutch plate?

– Warping on your plates can be measured. Just lay the plate on a flat surface, take a feeler gauge, and check the gap on the inside and outside of the plate. Then, subtract the two measurements and if it is more than (.006) the plate cannot be reused.

What type of problems can a worn disc cause?

– An excessively worn disc face can cause two types of problems, insufficient stack height of the clutch pack and it can restrict the oil flow which results in overheating.

Any tips to help remove a stubborn gasket?

– A propane torch used carefully can soften it right up for an easy removal, but I think a heat gun works even better. It warms the gasket and sealant up just enough for it to slide right off.

What gasket compound, if any, do you use on a new gasket?

– It depends on what you are sealing; for cooling systems, say, a water pump, you can use some RTV silicone. For oil a light coat of aviation on the gasket does the trick. And sometimes, it’s better to not use anything at all.

What should the transmission pump pressure be on a 77V1 D8K?

– Minimum 365 psi, max is 415 psi plus or minus 10 psi.

What about the torque converter outlet pressure on a 77V1 D8K?

– 42 psi plus or minus 5 psi in third speed, brakes activated, and converter in stall.

How can I tell if my dozer’s torque converter has too much leakage or my scavenge pump is bad?

– Pull the plug on the bottom of the torque case. After running it for 5 minutes stop the machine. If you have over 1-2 gallon(s) of oil that drains out in your pan either the torque or your scavenge pump is bad.

What would cause my D6D transmission to shift slowly?

– Could be low oil pressure, adjustment of control linkage not correct, an air leak on the inlet side of the pump, or it could be that the load piston and or differential valve is not moving.

I have bronze-colored particles in my power train filter on my D6D, what is it?

– It’s an indication of clutch failure.

What would make aluminum particles show up in my power train filter on my D7G?

– A torque converter failure.

I received my oil sample results that I purchased, but what does the indicator mean?

– If excessive amounts of silicate (Si) and aluminum (A1) are found in the fluid it means the oil is contaminated with dirt. If high levels of copper (Cu), iron (Fe), and lead (Pb) are found it would indicate abnormal wear of the bronze friction discs and steel separator plates.

Have a question that wasn’t answered on our FAQ? Send it to us at and we will be sure to get you a thorough answer!