Volts dropped below 13

[xRide]

So I just changed my alternator because I was getting all kinds of message (see post...5 weeks and problems...). By changing the alternator, it seems to solved the problem. Truck running great so far. But I have been monitoring the volts. The volt go from 13.7 and 13.9....only those 2 readings come up on the screen. However, whenever I HARD BRAKE where the tranny and everything is under a sudden pressure, it dips to 13.1, one time i saw it dipped to 12.8.

Is this normal?

I do have that 2 to 1 hard gear down on the tranny.

[TerminatorX5]

voltage fluctuation is normal - the hard braking is not normal... lol...

after dipping, it rebounces back, right? when such a change occurs with an external event, like in this case, hard braking, it is within the range unless the dipping is into 5-9 volts or so...

how often are you hard braking? are you racing the car? because if the car is raced, there are many other components that need to be upgraded to heavier duty versions - the brakes, the brake fluid, the cooling system, tranny cooler might need to be installed, some weight needs to be shed off the car...

[xRide]

lol.. no i dont race it. I did those hard braking to test it to make sure everything is functioning as they should. But it bounces right back to normal once its stopped or driving normal.

[AquilaBMW]

Voltage fluctuation is normal. Also, with the other symptoms you mention like the hard shift from 1 - 2, that might be adding to the fluctuation.

I recently learned that with the M62TU motor (not sure what year yours is), under breaking the vacuum system sucks quite a bit through the Brake Booster lines to help decelerate the engine. If there is a leak there or the vacuum line to the brake booster is bad - it can make the RPMs drop about 50 - 100 RPMs lower than it should.

If / When this happen, the engine essentially cuts out for just a brief moment, but enough to create that lurch or jerk into first. Next time you are driving.... see if you can observe your Rev Gauge while you are slowing down for traffic. Watch the needle and see if it briefly dips to or below 500 RPM.

Other causes could be a dirty or bad MAF. Also, how many miles on the transmission? Has there ever been a transmission service done. Low or filthy oil may also contribute to this symptom.

Some ways to fix are to reprogram your Idle Running speed with something like INPA, clean the MAF and if necessary, service the transmission.

[TwinTurboGTR]

It sounds normal. I'm thinking of it in a way that you are hard braking... The computer bank at NASA are kickin on AKA your X and the computers are going into overdrive trying to figure out how to get you out of a sticky situation involving ABS, DSC, etc. And those units suck a lot of power.

[xRide]

Originally Posted by AquilaBMW

Voltage fluctuation is normal. Also, with the other symptoms you mention like the hard shift from 1 - 2, that might be adding to the fluctuation.

I recently learned that with the M62TU motor (not sure what year yours is), under breaking the vacuum system sucks quite a bit through the Brake Booster lines to help decelerate the engine. If there is a leak there or the vacuum line to the brake booster is bad - it can make the RPMs drop about 50 - 100 RPMs lower than it should.

If / When this happen, the engine essentially cuts out for just a brief moment, but enough to create that lurch or jerk into first. Next time you are driving.... see if you can observe your Rev Gauge while you are slowing down for traffic. Watch the needle and see if it briefly dips to or below 500 RPM.

Other causes could be a dirty or bad MAF. Also, how many miles on the transmission? Has there ever been a transmission service done. Low or filthy oil may also contribute to this symptom.

Some ways to fix are to reprogram your Idle Running speed with something like INPA, clean the MAF and if necessary, service the transmission.

59k on the car now. i dont know if the tranny has ever been serviced.

i just got the ride in june. have not done any tranny work