Here's the deal, my 98 Ram will pop out of overdrive during long trips (and hour or so) at highway speeds (80-85 mph). The O/D light on the dash lights up, and I can't turn the overdrive back on for about 10 minutes or so. It's like a sensor or something is getting heat soaked, kicks the OD off, then when it cools down I can turn it back on. Any ideas?

Also, the truck kind of surges when leaving from a complete stop. It kind of bogs down when you hit the gas, then when it hits around 3k rpm it runs fine and takes off like a bandit.

Ian

 

That trans is basically a 3-speed auto with a seperate overdrive gearbox bolted onto the back of it. The oil passage between the main trans and the overdrive unit is too small. It is not uncommon for the OD unit to overheat due to lack of lubrication. They fixed this problem I believe in '99 or '00.

Best suggestion is to flush the trans fluid, change the filter, and adjust the bands. Also, pull both cooling lines off the driver's side of the trans and blow them out with compressed air (they tend to plug with crud) and replace the cooler itself with a large aftermarket unit.

 

Yuck! Automatics!

Bogging down until you hit 3K rpms? More like 2.8K, am I right? 2.8K has always been the speed at which Chrysler engines are tuned, even back as early as the 50's. You're going to notice a lag until you reach around 2.5 to 2.8, then it'll feel like someone just cranked some nitrous into your intake from 2.8 to about 3.5K rpms.

This is VERY VERY noticable when you've got some engine issues. Is there a lifter tick present? A leaking plenum pan severely amplifies this feeling. Before I fixed that gasket, my truck almost "chugged" along until about 2.8K RPMs, at which point, it took off like a bat outta hades. Also, check your engine's vacuum, check the vacuum hoses, and check vacuum related components, like the EGR valve, and the EGR solenoid. Also, check that PCV valve as well.

 

Thanks for the info guys. I do have a fluid/filter change and band adjustment planned next week for the truck, because I have an APS valve body w/trans-go shift kit and a deep pan on the way. I'll do what you say and blow out the cooler lines.

Yes, Buffalo, you're right, it's more like 2,800 rpm. There's no lifter tick present, but I'll check the plenum pan. From what I've heard, the plenum pan leak is pretty common on the Mag motors. No EGR on the truck, but I'll check the PVC and vacuum system too.

Thanks guys.


Ian

 

I have a 99 1500 EXTcab 4x4 with auto trans, and have had the same overdrive problem. It happened to me both before and after I had a complete transmission overhaul.

As far as the bog down issue, same here again. I do hear a slight lifter tick on mine.

 

Silver, I'm having both of those problems. I just had a rebuild done and I'm experiencing the same downshifting problem. I also have the ticking problem. What was done to fix these?

Thanks,
Highway

 

Theres a check valve in the pressure line from the tranny that plugs with normal crud. Best to replace(as in remove)it and add an after market cooler. BTW, this issue tends to be a source of that "second tranny in a matter of days/weeks syndrome."
Chances are pretty good you're gonna need new lock upselenoids if you've never done then.
As far as surges/lack of power...based on the symptoms it may not be only the plenum gasket. You may need a new TPS, and you might want to clean out the IAC passages and clean or replace the IAC. Thats the device on the back of your throttle body , and it controls airflow into the motor at idle.