Transmission Blues: Learn How To Service Your Diesel Transmission

Transmission Blues: Learn How To Service Your Diesel Transmission



Does your truck shift funny? Will it not shift at all? Has it gone into limp mode? If you answered yes to any of these questions, then your truck has a case of the transmission blues. Here is a step by step process you can do to diagnose it further.

The first thing that you should do is have the transmission fluid and filters serviced. This is not a real technical job, but it is a bit messy because you have to remove the transmission pan to get to the internal filter. In order to do this you will want the transmission warm, but not too hot if possible. Since you will be dealing with hot oil you don’t want to get burned in case it spills on you. Some transmissions have a drain plug, but many of the older transmissions do not have a drain plug so the only option for draining the fluid is to get the pan down. Identify which transmission style you have and prepare accordingly. Once you get the pan down and the fluid out, inspect the bottom of the pan before completely dumping out the residual oil. You want to look for any flakes of material or debris in the pan. Also look at the color and smell of the oil. It should be red to dark red. If it is black and smells burnt, you could have a problem or you have overheated the fluid. If you find debris in the pan, then you are most likely too late for saving the transmission and it will need to be removed and repaired.

If there is not any sign of debris in the pan, then go ahead and remove the filter from the bottom of the transmission. There may be a bolt holding it in, but most are just pushed up into the transmission. Once removed, inspect the tube and make sure the seal or o-ring has also come out. If not, you will need to get it out before installing the new filter. Once the new filter is installed, clean out the pan with a rag and some solvent. Make sure the sealing surface is clean on the transmission and the pan. Install the new gasket that should have come with your filter kit. Some of the new transmissions use a reusable gasket, but you will need to verify this. Put the pan back up and install the bolts and tighten to the specified torque.

Then install the required fluid into the tube where the dipstick was until it registered on the dipstick at the cold level. Next, start the engine and let the transmission get to operating temperature. Also shift it into and out of gear. Once the transmission is warmed up, check the fluid level. If it is near the hot level marks, then take it on a test drive to help get it to full operating temperature. After the test drive check the level again and add fluid if needed.

If, after changing the fluid and filter, the operation is back to normal you are good to go. However, if it is still having issues you will need to take it to a transmission repair facility to have it diagnosed and repaired. When it comes to diesel transmissions, find a reputable company that specializes in repairs to the type of transmission you have. If you have made power upgrades to your truck, then you will want to make sure that they take this into account. A stock transmission won’t survive when you have added extra horse power and so you will want to upgrade the transmission to be able to handle this extra power.

Once repaired and your transmission has cheered up, you can then tow or haul anything you want and not worry about having any issues.