I have a 94 that was a manual from the factory. The transmission is an automatic. I have replaced the sensor on the rear axle, the computer, the transmission itself, the speedo, the rear brake housing and the bulb, the fluid is great its new too. When I drive I feel a clunk I guess and the vehicle rocks from from front to back. When I put it in drive or any other gear it rocks too. Something just isn't right. Any help appreciated.

 

welcome to FTE, what shape is the driveshaft in, rear end have to much play?

 

More info, engine? trans? what is ECM #, did you get a harness for that trans, and a MLPS also?

 

What automatic transmission, E4OD, AOD, C6?
When parked into drive, or while driving?
Rocks? please explain.

 

trans is a e40d, motor is the i6. I did not get a harness and we did get the mlps too. When i park it it rocks when i out it in drive or reverse it rocks kinda feels like so.ething is holding it back. When it shifts it rocks too. It isn't as bad when I first got it. The whole truck used to shake bad now it shakes a little and I hear a pop. When I got the new computer I gave the guy my Vin and he asked if I changed anything else from. The factory me nor the previous owner did gotta look back to find the ecm number.

 

Thanks! From what I can tell the drive shaft is OK.

 

It sounds like you’re describing a swap or repair involving the Ford E4OD behind a Ford inline-6 (300 I6), and now the truck rocks or jerks when going into Drive/Reverse and during shifts, sometimes with a pop. From what you wrote, a few things stand out.

1. Missing or incorrect wiring harness

You mentioned you didn’t get a harness but did install the MLPS (Manual Lever Position Sensor). On an E4OD this matters a lot because the transmission is electronically controlled by the ECM/PCM. If the wiring isn’t correct:

• The computer may not know the gear position
  
• Shift timing and line pressure can be wrong
  
• It can cause hard engagements or rocking when shifting
  

If the harness is mismatched or partially wired, the transmission may default to high line pressure, which causes very hard shifts and jerks.

2. MLPS alignment

The MLPS must be perfectly aligned in Neutral during installation. If it’s slightly off:

• The PCM thinks the truck is in a different gear
  
• It can cause harsh engagement, popping, or rocking
  
• The truck may slam into gear
  

Many E4OD issues after install are just misaligned MLPS sensors.

3. Wrong computer (ECM/PCM)

You said the computer guy asked if anything was changed. That’s important because:

• E4OD trucks require a PCM programmed for E4OD
  
• Some 300 I6 trucks originally had the C6 transmission
  
• If the PCM calibration doesn’t match the transmission, shifts can be wrong.
  

Once you find the ECM/PCM number, that will help confirm if it's correct.

4. Engine / transmission mounts

The rocking and popping could also be mechanical:

• Broken engine mount
  
• Bad transmission mount
  
• Loose crossmember
  

If the mount is torn, the engine twists when it engages gear, which feels like the whole truck rocking.

5. Driveline slack

Also check:

• U-joints
  
• Driveshaft play
  
• Differential backlash
  

A bad U-joint can cause a clunk or pop when the transmission loads up.

6. Torque converter / line pressure

If the transmission is working but engagement is very hard, it might be:

• Line pressure too high
  
• Wrong EPC control from PCM
  
• Sticking valve body
  

But wiring/PCM problems are more common right after swaps.
✅ Things I would check first (in order):

1. Confirm the PCM/ECM number matches a 300 I6 + E4OD truck
   
2. Verify MLPS alignment in Neutral
   
3. Check engine and transmission mounts
   
4. Inspect driveshaft U-joints
   
5. Confirm the E4OD wiring harness is correct
   

This kind of issue is actually pretty common on E4OD swaps.

 

Do you know if its a MassAir, or Speed Density, truck, do you know how to tell?
If its Speed Density, there's 4-5 ECM's that can work $200-350, range.
I hope you have junkyards near you, you'll need the correct harness(E4OD) for the correct ECM to tell it how to shift.
This is the pin outs E4OD has its own.
Ford Fuel Injection

 

You should be able to find a stand alone E4OD controller
Speedway comes to mind
That might be easier than trying to find a Ford processor and good E4OD harness