Need help diagnosing a shudder on acceleration (1 Viewer)

[Ethel]

I need help from the collective diagnosing a shuddering issue on acceleration and under load I am having with my 92" 80 series. I have combed through the forums and thought I had found the solution a bunch of times...but no joy yet.

She is a 92 so 3F-E engine & A440f 4 speed auto tranny.
On startup she idles fine - comes down to 650 once warmed up.

Once I start driving things start to go south. I live on a short downhill so no real problems there but once I start to drive uphill she starts to struggle. She shudders and shakes to the top of the hill. The shuddering remains on acceleration under load...especially if driving uphill. It is really pronounced if I have to drive uphill from a standstill (turning, a stoplight, stop sign, etc...). When I can coast (downhill or after building momentum) there is no shudder - it only seems to apply when using the accelerator. Over the course of a 15 + minute drive it gradually evens out and eventually the shudder almost (not completely) goes away. I know that the 3F-E is considered underpowered...but when shuddering her up a hill it feels really weak - like it would if you shifted a manual tranny way too early. I have also noticed that my gas milage has plummeted to about 7 mpg.

I can't really tell if the shuddering is coming from the engine or the transmission. No wheel shake or vibes from the seat so I don't think its a driveline issue. Whatever it is seems to self correct after driving for a while - almost like something is swelling and correcting a leak (gasket or vacuum) somewhere? I would not say it is related to the engine warming up though - I can let her idle in my driveway for 30 minutes at operating temp and the symptoms remain the same once I start driving.

Things I have done so far:

• Cap/rotor/plugs/wires.
• De-smogged to eliminate potential vac leak areas.
• Checked for vacuum leaks (sprayed carb cleaner in all suspect areas - no change in idle)
• Checked & swapped every fluid & filter in her a couple of months ago. Thermostat is new.
• Adjusted the kickdown and throttle cables to factory spec (+ a little to compensate for 30 years of cable stretch)
• Oil is clear, ATF is nice and red, Coolant looks as it should.
• Inline fuel filter is only a year old.
• Service records indicate that the PO swapped in a new fuel pump and sock a few years ago.
• Replaced PCV valve and all of the air hoses leading into the TB.
• Checked the OBD 1 - no codes
• replaced the O2 sensors
• checked the motor mounts -they are solid.
• Grounds are all good and I don't see any potential for shorting of the wire loom against the rear firewall (although that seems to be more of an issue with the next gen 80 series engines).

Things considered but not yet pursued:

• Fuel injector issue? They seem to be buried awful deeply- is there any way to assess their health w/o digging all the way to them?
• Transmission issue (maybe it isnt warming up until I actually start driving and that is why driving for 15+ minutes seems to get things running better?) Since it is a hydraulic system w/o solenoids though...well that is out of my realm of understanding or ability to know how to troubleshoot.
• Head gasket or other issue with the head? But wouldn't she have other problems at idle or problems that would get worse once driving for a bit instead of the inverse?

I am running out of ideas. Any 80 series 3F-E gurus out there have anything?

 

[ppc]

What happens when you lock the CDL under the same conditions?

 

[Ethel]

What happens when you lock the CDL under the same conditions?

Ill try that next- what would it indicate if that changed things?

I did have the CDL locked for a week when I had my front drive shaft removed for re-balancing though. Did not change this issue.

 

[ppc]

Possible striped drive flanges or something other than transmission/engine issues.

 

[Kernal]

(batman signal)
Help @jonheld

 

[jonheld]

Is this a new issue that just started out of the blue, or did this issue manifest after doing some work on the truck?
If you try to increase speed when going uphill, does the transmission downshift to a lower gear when you put your foot into it?
During the "shudder" do your RPMs drop?

 

[Ethel]

Possible striped drive flanges or something other than transmission/engine issues.

Tried it with the CDL but no luck. Thanks for taking the time to give me a lead though!

 

[Ethel]

Is this a new issue that just started out of the blue, or did this issue manifest after doing some work on the truck?
If you try to increase speed when going uphill, does the transmission downshift to a lower gear when you put your foot into it?
During the "shudder" do your RPMs drop?

So it was like this when I bought her - it has just gotten progressively worse over the course of the last month. At first it was mild and I was hoping that I could correct it with maintenance and troubleshooting but...nope.

RPMs stay between 1800 - 2000 as she shudders her way up. If I floor it she lags and then jumps from 1800 up to around 3K

 

[jonheld]

So it was like this when I bought her - it has just gotten progressively worse over the course of the last month. At first it was mild and I was hoping that I could correct it with maintenance and troubleshooting but...nope.

RPMs stay between 1800 - 2000 as she shudders her way up. If I floor it she lags and then jumps from 1800 up to around 3K

So when the transmission downshifts and the RPMs go up, is the shudder still there? Can you climb the hill at 3K+?

Have you tried manually shifting the transmission?

 

[Ethel]

So when the transmission downshifts and the RPMs go up, is the shudder still there? Can you climb the hill at 3K+?

Have you tried manually shifting the transmission?

I can climb just fine and without much shudder at 3K. I can also manually downshift to 2nd gear and it climbs a little better...but I can still feel the shudder.

 

[Ethel]

I’m no guru when it comes to YouTube etc… but I think I made the short vid that I shot when driving uphill earlier today available.
I am steadily adding gas as I drive up the hill but the rpms stay the same and she just shudders weekly along...until she jumps. Not long after that I let off because I am approaching the top and would run out into traffic if I kept it going.

 

[jonheld]

I can climb just fine and without much shudder at 3K. I can also manually downshift to 2nd gear and it climbs a little better...but I can still feel the shudder.

Are you certain this isn't driveline related? It's pretty easy to remove 1 driveshaft at a time and hit the CDL button and go for a test drive.

If you're positive that it's not the driveline, then I'd be checking fuel pressure according to the FSM. Who knows what kind of fuel pump the PO used.

Also, the 3FE will spit out aftermarket ignition parts faster than you can put them in. Try to keep everything under the hood OEM.

 

[Ethel]

Are you certain this isn't driveline related? It's pretty easy to remove 1 driveshaft at a time and hit the CDL button and go for a test drive.

If you're positive that it's not the driveline, then I'd be checking fuel pressure according to the FSM. Who knows what kind of fuel pump the PO used.

Also, the 3FE will spit out aftermarket ignition parts faster than you can put them in. Try to keep everything under the hood OEM.

Yup -I have used OEM at every turn. You are right re not knowing what the PO used for a pump though. Ill look for how to check pressure next.
I am 99.9% sure it is not driveline related but will try the 1 at a time DS idea. Given that the issue is 100% gone when traveling at speed downhill or in neutral though...wouldnt driveline issues persist?

 

[jonheld]

I’m no guru when it comes to YouTube etc… but I think I made the short vid that I shot when driving uphill earlier today available.
I am steadily adding gas as I drive up the hill but the rpms stay the same and she just shudders weekly along...until she jumps. Not long after that I let off because I am approaching the top and would run out into traffic if I kept it going.

That motor sounds awful from what I can hear. A well tuned 3FE sounds like ball bearings in a blender on a good day, but yours sounds more like a diesel. Hard to hear on the video, but it doesn't sound right to me.

When was the last time the valves were adjusted?

General Tech - 3FE Tune Up Info

3FE Tune Up Info

forum.ih8mud.com

 

[jonheld]

Yup -I have used OEM at every turn. You are right re not knowing what the PO used for a pump though. Ill look for how to check pressure next.
I am 99.9% sure it is not driveline related but will try the 1 at a time DS idea. Given that the issue is 100% gone when traveling at speed downhill or in neutral though...wouldnt driveline issues persist?

In neutral or downhill there isn't a load on the driveline. Depending on what the problem is, it might not manifest.

 

[Ethel]

That motor sounds awful from what I can hear. A well tuned 3FE sounds like ball bearings in a blender on a good day, but yours sounds more like a diesel. Hard to hear on the video, but it doesn't sound right to me.

When was the last time the valves were adjusted?

General Tech - 3FE Tune Up Info

3FE Tune Up Info

forum.ih8mud.com

No idea on the valve lash adjustment but it is on my to-do list. I have not heard others in action before but I had always heard that the 3F-E runs like a tractor so I kind of assumed that what I was hearing was normal. Keep in mind that this is how she sounds going uphill though. She not that rough when idling or running at speed - only when under load / on acceleration and especially uphill.

 

[Ethel]

In neutral or downhill there isn't a load on the driveline. Depending on what the problem is, it might not manifest.

Thank you so much! You have given me a new to-do list to try and correct this thing:
1. Pull driveshafts and check..
2. Fuel Pressure check.
3. Valve adjustment.

Ill let you know how it goes and again...thanks!

 

[jonheld]

Thank you so much! You have given me a new to-do list to try and correct this thing:
1. Pull driveshafts and check..
2. Fuel Pressure check.
3. Valve adjustment.

Ill let you know how it goes and again...thanks!

There should be ZERO rotational play in the slip yokes, and ZERO rotational play in the universals.
Move each universal through its range on both axies. There should be no notches or wear points on either axis, and they should feel somewhat firm. Not flopping around.

 

[cruiserdan]

What's the manifold vacuum like?

 

[BILT4ME]

1) Check the cable adjustment for the transmission and throttle cables. It may not be downshifting when it should so it's lugging.
2) Check to make sure that all plug wires are well seated on both ends.
3) Frequently when struggling under load, it's a fuel delivery issue. I'd take a serious look at the fuel sock and the fuel pump that was replaced.
4) Confirm the timing is properly set. Too far retarded can produce similar results under load.

I believe this is fuel or ignition related, not driveline.