Questions about the Electronic Speedometer and Voltage Regulator

[hrbergeron]

I am finishing up my 4L80E swap in one of my HMMWVs. I currently have two questions after everything is done.

I installed an electronic speedometer, harness, and sending unit. Everything is working, but the speed, according to the GPS on my phone, is off by 10 MPH too high, ie. showing 70 MPH when I'm really doing 60 MPH. Is there anyway I can adjust it? I have stock 24 bolt MT/Rs.

I installed a 200 amp generator a while back and now want to send the 14v+ to the rear battery so there is not a charging imbalance, just like in the A2 trucks. How does the voltage regulator work? I am seeing no voltage on the 14v+ side of the regulator when the engine is running. I have tried it with my spare regulator and got the same result. Does it require a voltage from the battery or some sort of draw to cause it to energize? I find it odd that both of my voltage regulators are not showing any voltage. The 24V side is working properly.

If it makes any difference...
1994 M998A1 HMMWV, 6.5 NA GEP, 4l80E with USSHIFT TCM, 242 transfer case.

 

[hrbergeron]

Clear lenses make all the difference

 

[TOBASH]

Who needs a speedo? Who needs lenses?

Ride ninety miles an hour as long as you got the almighty power sittin’ on the dashboard of your car.

LOL.

 

[mechanicjim]

For the voltage regulators on the 200 Amp, yes they need to see the battery before they will output Current/Voltage. and don't run loads directly off the Stud on the regulator run all 14v loads off the 12v battery. you will get a max of 50 Amps at 14V from the stud. but it'll vary Amps based on demand.

 

[hrbergeron]

I installed the correct speedometer gear for the gear ratio I have but the speedometer is still off by around 5-10mph. It now fluctuates whereas before it was constantly off by 10 mph. The orange gear is the new 35 tooth one. Thoughts?

 

[86humv]

Red 36 tooth gear goes in a 242 TC and normally on trucks with radials and 2.73 gears

 

[hrbergeron]

Red 36 tooth gear goes in a 242 TC and normally on trucks with radials and 2.73 gears

Hello 86humv,

First let me clarify that the red gear is the original I removed from the transfer case. Counted the teeth and it is 41.

According to HummerPartsGuy, he told me that there are 3 different speedometer gears; Orange 35 tooth designed for 2.56 gear ratio, Red 36 tooth designed for 2.73 gear ratio, and another Red 41 tooth designed for 3.08 gear ratio.

HPG and the other HMMWV parts suppliers don't carry the orange 35 tooth speedometer gear anymore, but the gear is the same one used in 1990's Jeeps and Chrysler products because they used a NP 242 transmission too. The P/N is 52068157.

My HMMWV has 2.56 gears, so I swapped in the orange gear. I'm fairly certain that the speedometer is still off, but I will check next week again. It may have been rain mixed the GPS speedometer I was using as a reference, because at one point it said I was doing 124 MPH.



So basically, my issue is that my electric speedometer is still not accurate, even though I swapped the gear. It wasn't accurate before I swapped the speedometer to electric either. I have stock tires on this HMMWV.

 

[Milcommoguy]

If you kept the back wheels on the ground, maybe you could get an accurate read.

Now out of shoot three the "Tan Hmmwv" CAMO

 

[86humv]

I'm sure you know the metal gear housing has a specific spot kit gets installed to depending on tooth count.

 

[86humv]

I have lots a sending units also available

 

[hrbergeron]

I have lots a sending units also available

You sold me this one, lol.

 

[hrbergeron]

Today I readjusted the speedometer gear into the right setting on the guide according to how many teeth I have on the gear. I didn't even see any numbers the first time because of the crud on it.

I'm still having the issue of the speedometer being off at different amounts at different speeds. Before with the 42 tooth, at least it was always off by 10 MPH, not some variable amount.

Thoughts on more actions to take? Maybe try different positions of the gear?

 

[Milcommoguy]

What make you think the speedo is linear or to track in its calibration? Could be out of wack, balance, rusted, busted on the inside.

Military low bid?

Took one apart as kid and never did figure it out. CAMO