Transmission Oil Temperature Gauge

Published in the July 2013 Issue July 2013 Installs

If you use your truck to do a lot of towing, you should consider installing a transmission oil temperature gauge. The gauge is designed to accurately monitor your transmission oil temperature and warn you before excessive heat ruins your transmission fluid or causes any damage. High heat conditions are destructive of both transmission friction materials and transmission components.

For this install we went with the Transmission Temperature Gauge Kit—White Face (Part Number 80226) from B&M Racing. It retails for $53.48 at the www.bmracing.com website and based on prior experiences, we’ve found the extremely accurate and dependable B&M temperature gauges to be very easy to install. Plus this gauge will work with all 12-volt negative ground electrical systems. Transmission operation in the normal operating range of 150 degrees to 250 degrees will ensure long life and dependable service and having this gauge will help monitor those temperatures.

STEP 1

Disconnect the positive terminal battery cable to prevent accidental shorts and/or damage. To mount the temperature gauge, first decide how you want to do it. After searching for the best spot that would be visible to the driver, yet not take up a lot of room, we decided to mount it on the side of the pillar.

Drill a 2 1/16-inch hole into the surface for the gauge and then position it in mounting hole. Then use one brass flat washer, one lock washer and one nut on each stud. Next rotate the gauge until it is properly aligned and then tighten each nut finger tight.

STEP 2

Locate the oil return line to the transmission. On this Dodge transmission, this is the line that is to the rear of the transmission case. Note: this location is recommended to monitor the true transmission temperature going in, as well as to check the oil cooler efficiency.

Cut the steel tube oil line in a convenient location using a tubing cutter or hacksaw and carefully debur the ends of the tubing. Next select the proper T-fitting and then tighten the compression nuts securely. Be sure to double-check that the T-fitting holes are bored through all the way.

STEP 3

Place a small amount of sealer on the threads of the T-fitting, then install the proper coupler and tighten securely. Next place a small amount of sealer on the threads of the temperature gauge sender unit and then install the sender unit into the coupler and tighten very lightly.

STEP 4

Run a length of wire from the temperature gauge to the sender unit using the wire supplied with the kit. Bare 1/4-inch of the end of the wire supplied at the sender unit. Install an eyelet terminal supplied with the kit on the end of the wire and crimp it tightly with a pair of pliers. Install the terminal onto the sender unit stud. Install nut onto the stud and tighten securely. Be sure the terminal does no touch the body of the sender.

Tape the wire in position so it cannot touch any hot engine components and be sure that the base of the sending unit is properly grounded. A sending unit installed in a rubber cooler line is not properly grounded and an improper grounding will cause a false reading.

Install another eyelet terminal on the end of the temperature gauge wire and remove the nut and lock washer from the left-hand stud on the temperature gauge. Install the terminal onto the stud and install lock washer and nut. Be sure to tighten the nut snugly, but do not over-tighten as this could distort the bracket or damage the gauge.

STEP 5

Run a length of wire from the temperature gauge to the ignition switch or fuse block using the wire supplied with the kit. Bare 1/4-inch of the end of the wire at the temperature gauge. Install an eyelet terminal on the end of the wire and crimp it tightly with a pair of pliers. Remove the nut and lock washer from the right-hand stud on the temperature gauge. Install the terminal onto the stud and install lock washer and nut. Once again tighten the nut snugly, but do not over-tighten. Connect the other end of wire to an accessory or ignition circuit that is “hot” when the ignition key is on. Be sure not to allow the “hot” wire to touch the sender terminal on the temperature gauge.

STEP 6

Tighten nut and lock washer on center ground terminal snugly. Note: If you have mounted the gauge on an insulated panel such as a plastic dashboard, you will have to run a ground wire from the center terminal to chassis ground (frame or body).

STEP 7

Run a length of wire from the temperature gauge to the dashboard instrument light wires or terminal board. Bare 1/4-inch of the end of wire at the temperature gauge. Install the female spade connector furnished and crimp tightly with a pair of pliers. Slip connector onto gauge spade terminal. Tape or fasten all wires up out of the way from heat or any moving parts to prevent damage.

STEP 8

Re-connect battery cable and turn ignition key on. The gauge will read the oil temperature and after starting the engine you should check the T-fitting for leaks. As the transmission oil temperature warms up, the gauge will indicate properly. Turn on lights to check operation of illumination bulb.

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