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- Joined
- Feb 24, 2024
- Messages
- 515
- City
- North Carolina
- Vehicle Year
- 1994
- Engine
- 4.0 V6
- Transmission
- Automatic
Evening!
Apologies for the long post, TLDR at the bottom.
I'm hoping to get some feedback and help on further diagnosis for my 94 4.0 4X4.
Since buying it in Feb this year, i get a shudder/vibration when driving ~45-55mph, it shifts into OD, rpms drop to ~1700 and i attempt to accelerate.
I'm pretty handy, learn quickly but definitely need help early and often. I've done a significant amount of work to it, replacing worn out components and performing overdue maintenance:
-replaced all the ujoints and carrier bearing on the rear drive shaft
-replaced the transmission and engine mounts
-installed a shift kit on the A4LD valve body
-rebuilt shift motor and replaced transfer case fluid
-replaced spark plugs with Autolite 2X platinum's and ensured the resistance on the wires were within tolerance
Each of these repairs has given me a better working knowledge of the truck and helped me get a little closer to figuring out (by process of elimination
) the 'real' problem causing the shudder.
I've been reading through the service manual and if my understanding is correct the A4LD has 4 forward gears + OD. When using the OD option and in the correct circumstances, the PCM signals the shift from 3rd to 4th gear overdrive, reducing engine rpm by 25%. This is an electronic signal to the toque converter clutch solenoid, which hydraulically operates the piston-plate to provide lockup (solid drive) and unlock functions. Further, the TC clutch can be applied in 3rd gear in the D position AND in 4th in the OD position.
I've taken it on a number of highway speed test drives (55-65mph) and here are my observations:
-When driving in the D position, i don't experience the shudder issue. I initially thought that might be due to the specific rpm range that's utilized at those speeds (2k+ rpms at 55+). After reading in the manual that the TC clutch can be applied in 3rd gear (manual refers to this as 'direct drive'), I'm fairly certain that the TC clutch is not locking up at any point in the D selection. I believe it SHOULD be locking when i get to a cruising speed (say 55 mph) and less acceleration is used, but i don't feel it happen nor do i see the engine rpms drop.
-When driving in the OD position, once i get to ~55mph cruising speed, I feel the shift (presumably from 4th to overdrive) and engine RPM's drop to ~1700rpm. The TC clutch SHOULD be locked up, providing solid state driving. However, whenever i apply any acceleration in this condition, I get the shudder. When this occurs I have to give it more gas (presumably to unlock the TC clutch) and move into a higher rpm range (2k+). As soon as i let off the gas and re-enter a cruising speed, the entire sequence of events repeats.
TLDR
-When driving in D mode, i don't believe the TC clutch is locking up after achieving cruising speed and letting off the gas. My rpms do not drop and I do not experience the shudder in this driving mode.
-When driving in OD mode, the PCM is signaling the TC clutch to lock and my rpms drop from ~2300 to ~1700 (at 55mph), but when i give it any gas to maintain cruise speed i get a nasty shudder. I have to give it more gas to kick up rpms and get out of the shudder. Once i achieve cruise speed again, the scenario repeats itself.
Help me with the next steps:
-Is this shudder occurring b/c the PCM is telling the transmission to go to overdrive, lowering the rpm and then TC clutch NOT locking up (TC clutch solenoid failure)?
OR
-Is this happening b/c the torque converter clutch itself is slipping/failing?
OR is it something else entirely?
Without having access to the Ford transmission tester the manual refers to, is there a way for me to test the above diagnosis?
If I don't ever do anything about it and only drive it in D mode, is that still indicative of a failing torque converter?
Thanks!!
Apologies for the long post, TLDR at the bottom.
I'm hoping to get some feedback and help on further diagnosis for my 94 4.0 4X4.
Since buying it in Feb this year, i get a shudder/vibration when driving ~45-55mph, it shifts into OD, rpms drop to ~1700 and i attempt to accelerate.
I'm pretty handy, learn quickly but definitely need help early and often. I've done a significant amount of work to it, replacing worn out components and performing overdue maintenance:
-replaced all the ujoints and carrier bearing on the rear drive shaft
-replaced the transmission and engine mounts
-installed a shift kit on the A4LD valve body
-rebuilt shift motor and replaced transfer case fluid
-replaced spark plugs with Autolite 2X platinum's and ensured the resistance on the wires were within tolerance
Each of these repairs has given me a better working knowledge of the truck and helped me get a little closer to figuring out (by process of elimination
) the 'real' problem causing the shudder.I've been reading through the service manual and if my understanding is correct the A4LD has 4 forward gears + OD. When using the OD option and in the correct circumstances, the PCM signals the shift from 3rd to 4th gear overdrive, reducing engine rpm by 25%. This is an electronic signal to the toque converter clutch solenoid, which hydraulically operates the piston-plate to provide lockup (solid drive) and unlock functions. Further, the TC clutch can be applied in 3rd gear in the D position AND in 4th in the OD position.
I've taken it on a number of highway speed test drives (55-65mph) and here are my observations:
-When driving in the D position, i don't experience the shudder issue. I initially thought that might be due to the specific rpm range that's utilized at those speeds (2k+ rpms at 55+). After reading in the manual that the TC clutch can be applied in 3rd gear (manual refers to this as 'direct drive'), I'm fairly certain that the TC clutch is not locking up at any point in the D selection. I believe it SHOULD be locking when i get to a cruising speed (say 55 mph) and less acceleration is used, but i don't feel it happen nor do i see the engine rpms drop.
-When driving in the OD position, once i get to ~55mph cruising speed, I feel the shift (presumably from 4th to overdrive) and engine RPM's drop to ~1700rpm. The TC clutch SHOULD be locked up, providing solid state driving. However, whenever i apply any acceleration in this condition, I get the shudder. When this occurs I have to give it more gas (presumably to unlock the TC clutch) and move into a higher rpm range (2k+). As soon as i let off the gas and re-enter a cruising speed, the entire sequence of events repeats.
TLDR
-When driving in D mode, i don't believe the TC clutch is locking up after achieving cruising speed and letting off the gas. My rpms do not drop and I do not experience the shudder in this driving mode.
-When driving in OD mode, the PCM is signaling the TC clutch to lock and my rpms drop from ~2300 to ~1700 (at 55mph), but when i give it any gas to maintain cruise speed i get a nasty shudder. I have to give it more gas to kick up rpms and get out of the shudder. Once i achieve cruise speed again, the scenario repeats itself.
Help me with the next steps:
-Is this shudder occurring b/c the PCM is telling the transmission to go to overdrive, lowering the rpm and then TC clutch NOT locking up (TC clutch solenoid failure)?
OR
-Is this happening b/c the torque converter clutch itself is slipping/failing?
OR is it something else entirely?
Without having access to the Ford transmission tester the manual refers to, is there a way for me to test the above diagnosis?
If I don't ever do anything about it and only drive it in D mode, is that still indicative of a failing torque converter?
Thanks!!
I appreciate the solidarity!
