I have a 1994 E150 5 liter engine and an automatic with OD. The van has 150JK on the clock but the tranny was mechanically rebuilt at 90K and my mechanic just did a fluild and filter change and said no debris in the pan. The symptom I can describe is that if I hear a noise that sounds like BBs rattling in a can, the tranny will hang in low, jump to netural or downshift to low as if it had a mind of its own. If I do not hear that noise, it shifts normal. Once I get thru the low thing, and get on the road, no issues. Does not slip or flair. The mechanic says that the engine is giving the correct signals to the tranny to shift per his analyzer but the tranny is not acting on it correctly. Mentioned something about selenoids in the tranny and I assume the valve body. I am from the school that started with a mechanical linkage connection at the carb to the tranny and then the vacuum modulator. Can someone explain the electronics age on this? Thanks.

Tom

 

Make sure he used the correct the fluid.

 

Mechanic is a Master ASE and factory trained Ford tech who went into buisness for himself after working for a local Lincoln dealer for 20 years. The problem predates his latest service. I should have made that more clear.In fact the problem started some years back and the original owner had it rebuilt at 90K miles but nothing changed. I think it a matter that the rebuilder knew the mechanical parts but not the electronic interplay. I am just trying to understand how it works, now.

 

Sure can. First, there is no mechanical linkage from the "carb" (or in this case 'throttle body'). Your transmission type is a 4R70W, an all electronicly shifted transmission. The PCM (Powertrain Control Module) monitors road speed from the VSS (Vehicle Speed Sensor) mounted on the rear end housing, engine rpm, throttle position (from the TPS), engine load (from the MAP sensor) and shifts the transmission based on a "shift map" stored in the PCM's memory.

Comparing this transmission to an old fashoned (non electronic) unit, the VSS replaces the governor where the governor fuction is regulated by road speed. The TPS replaces the kickdown linkage. And the TPS and MAP sensor replace the vaccume modulator and/or throttle valve linkage by providing the PCM with engine load data.

Your old fashioned transmission shifted via TV or modulator pressure vs governor pressure. When you stepped on the throttle the TV (throttle valve) moved raising TV pressure, or the drop in engine vaccum raised modulator pressure (depending on whether or not the transmission used a modulator OR a throttle valve). Then as the vehicle accelerated the governor (driven by the output shaft) began raising governor pressure. The TV or modulator pressure was applied to one side of the shift valve and governor pressure on the other. So when the vehicle went fast enough for governor pressure to overcome TV or modulator pressure, the shift valve would move and the transmission would shift. Then the process started over again for the next gear.

On your electronic 4R70W, the PCM monitors those same basic fuctions: Road Speed (governor pressure) and Throttle position/engine vaccum (TV or modulator pressure). Only now the shift map is used instead of the simple change in pressure. So as you step on the throttle and start accelerating, the PCM monitors all of those functions and when rpm, load and speed indicate a shift the PCM turns on or off one of the shift solenoids located on the valve body. The shift solenoid is a simple valve that opens or closes to route hydraulic pressure to a shift valve forcing it to move and therefore shift the transmission.

Your 4R70W, like most electronic transmissions, has three types of solenoids. Shift soleniods; there are two, which move the shift valves via turning on/off hydraulic pressure routed to the valves. A pressure control solenoid; which has much the same function as the TV or modulator does. It regulates the internal line pressure inside the transmission. It is line pressure that actually applies the clutches and bands and is what determines the change in shift firmness by raising or lowering line pressure as determined by engine load. Lastly is the TCC solenoid. The Torque Converter Clutch solenoid turns on and off the Torque Converter's Clutch.

I am not sure about your BBs in a beer can noise. I guess its possible that you have a solenoid that is acting up somehow but I have never heard of such a thing and I almost never see 4R70W shift solenoids go bad. Since the problem is on the 1-2 shift my first suspicion would be the intermediate roller clutch. This clutch must hold to apply 2nd gear and is one of the few weak links in a 4R70W. Plus, your '94 model would have the early style roller clutch. These roller clutches either hold or fully release, there is no slipping as you find with a regular stack of clutches in a drum.

I have an almost identical van, a '95 Clubwagon XLT with a 4R70W trans and 5.0 motor. I recently overhauled the transmission (at 232,000 miles) and found the intermediate roller clutch to be about shot. I replaced it with the newer style drum ('97 and up) that uses a "mechanical diode" which is much stronger than the roller clutch. I would suspect that your intermedial roller clutch has some kind of problem. These roller clutches make a buzzing sound when they overrun anyway and that might account for your noise. As for the problem predating the overhaul. Its common for the rebuilder to check the action of the roller clutch by hand and if it rolls one way and holds the other he assumes its good and re-uses it. This is not always the case because your can't put enough load on it by hand to see if it holds under load. So it is very likely that if this is your problem, the technician missed it on the rebuild.

Good Luck,
Steve
'95 Clubwagon XLT

 

Steve:

Thanks a million. I now understand how this thing ticks. Get this. I use this van primarily to transport cats to pet adoption days at Petsmart. When I drove it the other day, it was all over the lot in terms of this first gear thing. I cranked it up today and drove it 40 miles to a mall, drove it around on the busiest road in Jacksonville FL, drove it home, and it was perfect the whole time. Absolutely perfect. Go figure.

 

Yeah, they can be that way. When the roller clutch in mine started showing signs of trouble it would do it intermittantly. My van is used primarily to tow my racecar and most of those 200+K miles are towing, usually long distances.

Small world on the kittens. Just yesterday I had two stray females, that have been hanging out around my home for the last few months, spayed. They each had a litter of kittens a couple of months ago. I would love to keep them all but I already have two small dogs (both rescue Pekingese, one is blind) and an orange tabby (about one year old) that was a stray that turned up here last winter.

I recently found a local group here called "Friends of Ferrals" that cares for ferral cats and am working with them to find homes for everyone.

Steve
'95 Clubwagon XLT