Hey! ok so ple ase help me here I just bought a 98.5  cummins about a month ago and it has this issue that I just cant seem to tackle and its super frustrating! if I have ac on just cruzing along in overdrive (48+ mph) it jumps in and out of overdrive! but as soon as I turn the ac off.. no problem! it runs great.... turn it back on it goes right back into this cycle of going in and out of overdrive. when I first got it the ac worked but the fan didn't work so when I took it home and got to lookn at it closer I noticed a wire going to the + battery turminal and it had a blown fuse right there too.. replaced the fuse and fan works great now......    just tonight I put a APPS noise insulator on hoping that would fix it but it didn't... anybody got the same issue, or know a fix? thatd be super helpful!

25 minutes ago, Mopar1973Man said:

 

Doesn't guarantee noise free power.  They are nice big alternators typically a single wire. Still have no battery temperature compensation so battery life is shorter and diodes still fail in those as well.

 

i agree.  factory alternators are fine, the oem ones typically lasted over a decade.  the reman ones just arent that level of quality.  

 

imo, one of the killers of alternators is jump starting and connecting the cables when the vehicle is running.  that initial massive voltage spike from the arc kills diodes.  

I do a lot of jump starting of vehicles to especially those that don't start or being tough to re-prime up. Matter of fact it might of been the last job that killed my alternator on my truck.

 

ok so the problem strangly went away for awhile I didn't use any ac and then this week I started using it again and it hasn't been doing it at all!......... famous last words! today I was driving to town and about ten minutes in I came to a light .. stopped .. took off again and it wasn't running right since! its like the torque converter came "unlocked" for good! 60mph it runs like 2500 rpm.. took it to advanced and got a speed sensor but that wasn't the problem! .... so now idk what to think! could this be from the alternator you think? same problem? and then half way home my brake lite and abs light come on! so now I'm totally confused! help very welcome!

Did you replace the alternator?

1 hour ago, Me78569 said:

Did you replace the alternator?

no! I havnt replaced it yet! now my brake system is acting weird! my dash shows the abs light and the brake light! and my trailer controller in the cab as well as my tail brake lights are always on!! COULD THIS ALL BE FROM THE ALTINATOR DIODE PROBLEM??? I need to figure this out quick! because I'm supposed to hual a trailer 5 hours away tomorrow for a week long trip!

 

 

 

Edited June 25, 20168 yr by t-stack

ok fellas! so tonight I went to advanced auto parts and bought a new 120amp alternator. put it in and absolutely nothing changed!  soooo I'm totally at a loss now! I don't know what happened to my truck! can yall help me out? please! that would be fantastic! thanks

Test the new alternator for AC noise.

 

AC noise tends to burn up computers, longer you have it the worse off the computers are.

 

I would get some dielectric grease and check and lube every plug under the hood with it.  Apply it, then cycle the plug 5 or 6 times.

 

Look for any signs of corrosion on the pins and wires.

39 minutes ago, t-stack said:

I went to advanced auto parts and bought a new 120amp alternator.

 

I've seen several guys go through over 4-5 brand new alternators to just get one good one. Did you have it tested before you paid for it? Did you have the previous old alternator tested before you bought the new one? Do you test anything yourself using a DVM? If so what reading did you get? What happens if you unhook the field lead and remove the alternator fuse and go for drive?

Speaking for the electrically challenged here I understand why you just bought an alternator and threw it on. The advice you are getting is sound but you have to do some testing or you just end up with spare parts or new parts that are not much better than you had to start with and after trading in your core you are just stuck. This issue might be beyond your alternator but you will never know until you do some testing. You have to eliminate things to be sure of what needs to be done.  

Got the light problem fixed ... it was just a light switch went bad! ... although my torque converter unlocking issue still remains. I don't have my DVM at the moment but I unhooked the alternator and the fuse and took it for a drive and nothing was different! the same issue is still there! so hopefully ill get my Meter again today to test but it doesn't seem like its a alternator problem! is there anything else that could be causing the converter to unlock? its not the overdrive though because if I'm going 60 and hit the overdrive button it stil kicks into overdrive so it must be my torque converter.

how fast does it lock and unlock?  IE in 5 seconds how many times will it lock and unlock?  

 

Could be TC shudder from a bad TC. Could be a leak in the VB, or a bad lockup solenoid.

22 minutes ago, Me78569 said:

how fast does it lock and unlock?  IE in 5 seconds how many times will it lock and unlock?  

 

Could be TC shudder from a bad TC. Could be a leak in the VB, or a bad lockup solenoid.

well it doesn't even lock and unlock! it used to do that an then the one day it just stopped locking completely... so now I cant get it to lock at all

so you have 0 lockup?  

 

If so check out your boost valve in the valve body,

http://www.cumminsforum.com/forum/98-5-02-powertrain/622743-valve-body-parts-tranny-pan-help-i-d.html

 

 

On ‎7‎/‎4‎/‎2016 at 6:50 PM, Me78569 said:

so you have 0 lockup?  

 

If so check out your boost valve in the valve body,

http://www.cumminsforum.com/forum/98-5-02-powertrain/622743-valve-body-parts-tranny-pan-help-i-d.html

 

 

is the valve body hard to get to? does it just require taking the pan off?

You need to drop the pan, once the pan is dropped it is 6 or 8 bolts, nothing the average joe can't handle.

Is it hard on your tranny to  drive with the torque converter  unlocked?

not really, just creates more heat in the trans fluid.  I wouldn't tow like that.

On 7/6/2016 at 5:55 PM, t-stack said:

is the valve body hard to get to? does it just require taking the pan off?

ok so today i tore  into the tranny and got the valve body off and that small piece inside was still perfect so its not that! could it be anything else in the tranny- before i put it all back together?  what else could be causing the torque converter to unlock?

here are some photos

Looks fine.  The tc solenoid would be my next guess.

 

 

Before assembly I would clean the shaft/kick down shaft with sandpaper and brake clean before re-installing the valve body. This will prevent damage to the seal on the case. Transmission fluid look a bit darker than usual and discolored...