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Overdrive Troubleshooting

2K views 20 replies 6 participants last post by  feblock352 
#1 ·
1998 2500 5.9L V8 automatic with 3.5 rear end factory size tires 245/75R16

I just got this truck on the cheap which wasn't shifting out of 2nd gear so I installed a kit that had all this stuff:

One (1) Governor Pressure Solenoid (Borg-Warner Heavy Duty) Upgrade
One (1) Governor Pressure Sensor (Transducer) 56028196A
One (1) Output Speed Sensor (With O-Ring) 4800879
One (1) Lock-up and Overdrive Solenoid with Harness

Now I've got it back together it seems to be shifting smoothly.

At 70mph I'm running 2750rpm. This seems really high to me; seems to suggest that overdrive is not working? What is the typical rpm for running at 70mpg with overdrive engaged?
When running at 70mpg pushing the button does nothing, no change in rpm. So my question is, is my overdrive even engaging?
Note that when I try to use the overdrive button to turn off overdrive it does not appear to do anything (guage cluster light remains off which indicates Overdrive is still active). I've also tested the button (it is good) and even jumpered it manually, still no light, or rpm change.

I've looked at the no 3-4 upshift section of the 'Automatic Transmission Diagnostic Chart' and have a question about which fuse is the overdrive fuse, step 2? My owners manual doesn't have an overdrive fuse labeled?

Thank you.
 
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#2 ·
The fuse only supplies power to the light, It has nothing to do with engaging the od. The switch allows the ground connection to one of the pins on the pcm. I would suggest getting a wiring diagram and see if you have a ground from the switch on the pin. If you do then you problem is elsewhere. Did you reset the pcm after you installed all the new parts?
 
#4 · (Edited)
I think I reset the pcm. I just disconnected the battery, turned ignition on for 20 seconds and then reconnected the battery.
Many disconnect batt and turn/hold key in START/crank position for 20 sec; others disconnect positive batt cable and ground it for 30 sec.

Any codes? (so all required parameters/temps are met to engage OD)

... Some requirements from print version of 98 FSM: no 3-4 shift will occur if---
---OD switch is off
---trans fluid temp is below 50F (< misprint I think) or above 250F
---2-3 shift not completed
---vehicle speed too low
---amb is below -5*F (-17C)

... From what I gather, OD switch is momentary; BL/LG wire is ground to chassis?, OR/WT wire to PCM.

... Would count the shifts/events to see if converter is locking (TCC engaging) and holding properly and not slipping (Grrrrrr).
..No 3-4 shift will occur if TCC is locked up in 3rd, or PCM "thinks" TCC is locked up but TCC is slipping (will throw a code).
 
#5 ·
So I tried the pcm reset both ways as you said and no change in behavior. The button still don't work either.

Driving around town it seems like it shifts into 4th, but on the highway it seems like it must be sticking in 3rd. Can you confirm if 2750rpm makes sense for overdrive or 3rd at 70mph?

I'll keep poking around the wiring I guess.

Thanks.
 
#7 ·
There are no codes according to the obdII scanner. Is there a separate way to get tranny codes?
... No separate way that I know of; have "heard" talk of "deep memory" in PCM or something like that (ain't no expert in elec stuff at all).
..Your looking for any codes though, not just trans codes.

Driving around town it seems like it shifts into 4th, but on the highway it seems like it must be sticking in 3rd.

Can you confirm if 2750rpm makes sense for overdrive or 3rd at 70mph?
On a low traffic highway/road would manual shift it and watch tach: count shifts and if conv TCC "lockup" event occurs (tach will drop a 300-700 rpm depending how hard your on the throttle); "if TCC locks" drive for 2 more mi ensuring TCC does not slip; watch tach closely as yourelease/press throttle a bit without unlocking conv (if tach rises TCC is slipping).

... As said before, if TCC is slipping, PCM still thinks/KNOWS it's locked and will not allow trans to shift (3-4 or 4-3) till it unlocks.

... If TCC locks up in 3rd trans will not shift to OD/4th, push button and count shifts/events again.

... Whenever key is turned off then on, OD is automatically switched on (or should be!)

2750 at 70 will be 3rd; don't remember if that's with TCC locked/unlocked; will check my 3.55 tonight on the way home tonight.
 
#8 ·
Awesome info.

So it seems that when my rpm dropped I thought was shifting into overdrive was just the TCC "lockup" event.

Will driving my truck this way damage the tranny? Most of my driving is around town so I really don't need overdrive most of the time. Obviously though, I'm really hoping to get it working though for the times I would like to take it on the highway.

I'm hoping to borrow another obdII scanner to double check for codes. Last I checked though, the check engine light was off and there were no codes.

Thank you!
 
#9 · (Edited)
So it seems that when my rpm dropped I thought was shifting into overdrive was just the TCC "lockup" event.

Will driving my truck this way damage the tranny? Most of my driving is around town so I really don't need overdrive most of the time. Obviously though, I'm really hoping to get it working though for the times I would like to take it on the highway.
... Will not damage trans around town, actually/usually/normally it's better to select 3rd (no OD) in town.

... On level road, in 3rd with TCC locked up (and not slipping?????) at about 50+ mph, and a steady pedal/throttle; push button to deselect 3rd, tach should rise 2-300 ish rpm as TCC should unlock before it "tries" to shift 3-4; then TCC should remain unlocked till after 3-4 shift occurs (unless button is pushed again).

... For now, always watch tach at 50+ mph as you push button and wait for 3-5 seconds for trans and/or conv to respond, see what's happening; and to catch if TCC slips or starts/is slipping (remember, if PCM "thinks" TCC is locked up as commanded, it will/should never allow a shift).

... When key is first turned to ON, does OD light in cluster come on? (it's an inch ish to the left of gear indicator, just below red? seat belt reminder).
 
#10 ·
I can't get the OD light to come on for anything. It does not come on when first turning the key or pushing the button or using a jumper wire bypassing the button.

I haven't driven for a few days but from what I remember I suspect the TCC is slipping. Does that indicate a bad torque converter?

I'm not sure I can run your test completely because the button doesn't seem to do anything. I guess I will have to remove the guage cluster and double check the bulb.

I will have to run more tests as soon as I can. Might be a couple days before I get to it. I really appreciate your help!
 
#12 ·
on diesels this is a common problem but dont hear about it on the gas trucks but worth trying, get a volt/ohm meter and probe the alternater while engine is idleing, probe the battery charge on back it should not be more than 0.1vac, if it is then you will have problems such as lock/unlock of converter, also means your alternater is bad, it will cause damage to the computer and or other electronics, also you can do another test by disconnecting the alt. and removing the charging fuse and going for a drive.
 
#13 ·
His problem is not with the charging, He needs to start checking wires for voltage/ground on the switch. Then start checking the leads from the trans to the pcm for continuity. This is if the od is not working, Do what key said and count the shifts! This will tell you if it's in 3rd or od. My understanding is the lock up only happens after the od is engaged. It usually happens so fast you don't notice it. Sometimes in cold weather after you first take it out you can notice it buy looking at the tack after od engages it will drop another 200 rpm or so.
 
#17 ·
Being no codes and OD bulb is good, I'm guessing it's in the wiring as suggested by others (am assuming faulty TCC solenoid would throw a code, unsure); test circuits as moparite said.
... For shits and giggles, could drag brake a hair (so brake lights come on) too unlock TCC when trying to shift 3-4).

... 13.8V at idle is on the low side; these rams are real fussy about having a near perfect batt and charging system (although most complain of weird/odd engine behaviour, not trans).

... Due to ice/traffic etc, only got up to 68 mph in 3rd lock, had about 2800 rpm. (am guessing your 2750 @ 70 is 3rd lock)
 
#18 ·
My 98/99 Durango seems to have a possible similar issue. Had a 97 Dakota 6 cylinder and a 2000 Durango and on both I could push the OD button the light would come on, and see a difference in RPM's. On this one no change. I do appear to have other transmission issues that the may be a partial cause of. Will be watching.
 
#19 ·
as stated you are looking at AC voltage not charging voltage, ac voltage that is hi is caused by bad diodes in alternator, i will have to go into the cummins forum or 1973mans diesel forum or you can youtube checking ac voltage in a dodge ram cummins diesel its quick and ez to try, also bad or not so good grounds on the body and frame can cause issuses. i scrape the paint down to metal and re bolt the grounds.
 
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