Hi Everyone,

I am looking for some guidance about possible problems regarding an intermittent but increasingly frequent transmission issue. I have 94 dakota RWD with 3.9 V6 and a 42RH transmission (3-pin connector). The transmission is a reman unit that was installed about 3 years ago to replace the previous unit. Engine and tranny are stock and its a daily driver, light duty. The dodge factory "anti-drainback" check valve in the trans oil-cooler line was removed (more on that below) during the installation of a new oil cooler supplied with the reman transmission.

The issue is the transmission momentarily slips or "freewheels" from the engine when I first drive the truck in the morning, after it has been parked overnight on a level parking lot. Specifically -- I start up the engine, wait few seconds, then I Reverse just fine on a Slight incline uphill about 50 feet, then shift to a Forward gear (low or drive) to drive up the next portion of the driveway that is VERY STEEP (25-30 degrees) until i get to roadway above that is level. The transmission never slips/freewheels while initially Reversing out of the first short leg of the driveway. When I shift to Forward to go up the steeper section, the truck does moves forward firmly for about 20 feet or so then the slip/freewheeling event starts to happen. I usually put it in neutral, roll back to the landing, put it in Forward again, and leave it rev lightly until the transmission grabs hold again. Sometimes it repeats the issue one more time on the same very steep portion or above as i get on the level road. However, After this, once it grabs again, it works perfectly for the rest of the day. Good shifts, no slipping or freewheeling, etc in all gears. This includes even after its parked up during the day for 8 hrs, etc and driving up and down equally steep roads, pausing in traffic on steep roads, and on flat runs. Even when I come home during the day and leave again, the truck drives up that steep driveway just fine. It only occurs in the morning after sitting overnight (12+ hours). It feels like the transmission loses prime due to the steep incline. There are no odd noises, shudders etc. It just releases hold and eventually grabs again.

The fluid level in neutral is correct on the stick in the "ok" range. When the truck is shut off, the fluid goes about 1 inch higher on the stick. Fluid color is ok.

After looking online at possible causes etc, I read about the torque converter overnight draining issue of this series of dodge transmission and how the check valve in the cooler line prevents drain back. My check valve is removed as noted earlier. (I am getting a replacement for it.) Also read that the trans pump doesn't pump in Park and to run it neutral for a bit to fill the torque convertor in the morning before heading out. Even after running it in neutral on the flat parking for 5 plus minutes this morning, it still had the problem again today when I started driving forward up the hill.

What is concerning me is that it doesn't do this every single day when I leave that driveway. Many days it runs just fine. However its increased in frequency recently compared to the past. It could be it has lost a little bit of fluid, but it works fine on other steep roads afterward. And from what I have read, many folks say that the overnight drain down TC condition would not allow the truck to move AT ALL when first put in any gear (R or Forwards). My truck reverses just fine for that initial leg of the driveway. Also after leaving it run in neutral for a longer time to refill the TC, the slip/disengage still happened in Forward on that steep leg today. I could add some fluid but I am hesitant to overfill it and damage the transmission. I am wondering if I should cycle thru all the gears to ensure all the hydraulic circuits are filled/purged of air before heading out in the morning (maybe some circuits are not purged/filled after running in neutral)? It was working fine in the past with oil cooler line's drain back check valve removed. It only did this once every few months. Now its almost daily as noted above.

Any thoughts on possible causes would be appreciated. Sorry for the long read but trying to be as specific as possible.

Thank you

 

The front pump is disconnected when it's in park; try shifting through all the gears, leaving it in gear for 5 to 10 seconds, before you shift to reverse to back up, see if that helps.

And depending on how steep - you may actually be fluid starving the transmission at first.

There's a replacement valve for the 42RH ( Sonnax Manual Valve - 22771-09 ) that may help.

RwP

 

Thanks RalphP for the input. I shifted to neutral and thru the gears on first startup and it still slipped when I took off up that hill. I checked the fluid in neutral, warmed up and it was in the "ok" range just under the Max line on the stick. I added about 1/2 a quart of ATF+4 to the transmission and the level is now a tad over the Max line on the stick while in neutral. That seemed to work, as for the last few mornings, it has not slipped/lost prime at all. Back to its old self. So I guess its sucking air briefly when I take off up that steep hill.
I guess I'll just keep the fluid level (checking it in Neutral) at just over the max line. Hopefully that doesn't cause any damage or other problems? Also will check the Sonnax kit. I saw some Transgo Kits on RockAuto for this transmission. Are those any good?

Thanks again.
Dakdude.

 

I'm not sure about any other kits; I just remember that Sonnax part as I was looking to possibly build up a 42RH to replace my 31RH/A998 in my 1988, wanting a 4th gear or OD so I can also go a bit stiffer than 2.92 in the rear end (!!!)

When it warms up a bit, I bet it'll be OK at MAX or below.

If it's too far over MAX, then not only can it aerate, but it'll blow out the vent; but if it's not blowing any, it SHOULD be OK as long as it's not a quart over or anything.

But there's always tolerances. So if it's just over, it SHOULD be OK.

One more consideration - maybe a deep pan and a filter extension? So that there's more fluid around the pickup?

I don't find many inexpensive deep pans; my local boys have this one Transmission Pan, Dodge 904 / A500 / 40RH / 42RH / 42RE / 44RE, PML # 9862-AC Deep As-Cast - PATC - TransmissionCenter.net and that doesn't include the filter extension (to keep the pickup down in the deep pan).

Caveats: You may have to pay attention to the exhaust pipe routing, and it may require loosening the cross member to get it in.

If you find one at a better price, please post that here.

(I'd probably check out what TransmissionCenter.NET or PATC - same company - has first, then TransmissionBench.COM, then Sonnax and Transgo in that order. But PATC because, well, they're about 3 miles from my house and good ol' boys locally. That probably doesn't apply to you ... )

RwP

 

My guess would be front pump or a bad seal. Can't hurt to look at the filter.