speedometer sending location

Just replaced mine. Was about $73 if I recall. Seems inductive/magnetic pickup. Fixed speedo. I let it go a while and it got worse to Where speedo would jump to 90mph and the ECU would temporarily stop injection thinking it was over speeding. ..vehicle was at 60 mph on Fwy. Not fun. You'd think they Don't connect. Easy fix tho.

Electrix wrote:
The MD3060 has two black plastic Allison speed sensors that are held in by a 13mm head bolt. Both are on the right hand side of the transmission, and connect to the ECU.
The one near the front is used to measure engine speed.
The one on the rear housing is used to measure the output shaft speed.

The rear housing can also have a threaded hole for an optional speedo sender. This is on the left side of the drive shaft.
Do you have a sensor screwed into this threaded hole?

Thanks for the info I will check on the sensor in the hole.

The MD3060 has two black plastic Allison speed sensors that are held in by a 13mm head bolt. Both are on the right hand side of the transmission, and connect to the ECU.
The one near the front is used to measure engine speed.
The one on the rear housing is used to measure the output shaft speed.

The rear housing can also have a threaded hole for an optional speedo sender. This is on the left side of the drive shaft.
Do you have a sensor screwed into this threaded hole?

Electrix wrote:
John, the Allison MD3060 has three possible ways to operate a speedo;
1 - an output speed signal from the transmission ECU,
2 - a screw in speedo sender fitted into the rear transmission housing,
3 - a toothed wheel fitted to the rear flange and a speedo sender fitted to a bracket.

Option 1 is available from all Allison transmission ECU's.
Options 2 and 3 are fitted by the OEM if they don't want to use the ECU output.

How many speed sensors are fitted to the rear of your transmission?
The plastic one on the rear rhs is for the ECU. It has a single bolt with a 13mm head holding it in. It is fitted to all MD's and is not adjustable. You would have shift problems and the transmission fault light on if this was faulty.
The screw in speedo sender is on the lhs. Depending on the type it may be adjustable.

I have 2 sending units of some type held into the transmission by the 13 mm bolt as you have described. The ECU was rebuilt last fall and the problem started happening just prior to the ECU going out. I am trying to find the part numbers for the sensors that are on the tranny.

John, the Allison MD3060 has three possible ways to operate a speedo;
1 - an output speed signal from the transmission ECU,
2 - a screw in speedo sender fitted into the rear transmission housing,
3 - a toothed wheel fitted to the rear flange and a speedo sender fitted to a bracket.

Option 1 is available from all Allison transmission ECU's.
Options 2 and 3 are fitted by the OEM if they don't want to use the ECU output.

How many speed sensors are fitted to the rear of your transmission?
The plastic one on the rear rhs is for the ECU. It has a single bolt with a 13mm head holding it in. It is fitted to all MD's and is not adjustable. You would have shift problems and the transmission fault light on if this was faulty.
The screw in speedo sender is on the lhs. Depending on the type it may be adjustable.

I have a '93 HR on a Spartan chassis with the Allison 3060 transmission, and a Cummins 8.3 diesel engine. I had to replace the cruise control several years ago and part of that control connected to the speed sensor on the transmission. I've forgotten all the specifics involving the wiring, but it wasn't easy figuring out how to wire the cruise control since the instructions that came with the new control were all wrong.

My sensors were all at the engine & transmission and not at the front wheels. I would suggest checking the wiring at the transmission.