1986 with 60k miles. Seems to shift fine in or out of OD. Without OD, all gears shift and run smoothly. In OD, 2nd, 3rd, 4th, all shudder under about 2k rpm. Over 2k rpm, runs pretty normal.

I checked the fluid, all good. Checked the mount - looks ok....

i just kick kick it out of OD and drive it for now with OD.

anyone have any experience like this? I see a lot of posts on fluid and flushing and grinding, but nothing on vibrations!

 

What happens if you run under 2K RPM in all gears with the OD disengaged? Does it still shudder like it does with the OD engaged?

 

With the OD disengaged, everything is normal. All gears. No noise. No bucking. With the OD engaged, until you get north of 2k rpm, it bucks like you are lugging the engine like when you are not not giving it enough gas to get into first and its about to stall.

So running along at 60mph in 4th at 1900, all good. Put in the OD, settles to maybe 1600, go to accelerate and it might as well be like lugging the engine in 1st to get it rolling. Drop it out of OD or into 3rd with OD, it gets back up to 2k either way and smooths out.

Without the OD, everything it normal so I am assuming it is not a trans or clutch issue.

 

It seems to me to be an engine issue and not an OD issue. I'd look at the basic tune up condition, wires, plugs, cap, rotor. Check for plug wires arcing by running the engine in a darkened garage and looking for visible sparking. Check individual cylinders for proper firing by using an infra-red thermometer gun, pointing it at the exhaust ports where they come out of the heads. Look for one being cooler than the others and that will point you in a direction to start with. Good luck with this!

 

Thanks for the direction. Seems too simple but I was wondering if and how it could be an ignition issue. It just isn’t there out of OD but it is all low rpm engine running. The fuel system was worked over and cleaned out and tested last summer. It was tuned with new plugs and wires and HEI module, but maybe i did a shitty job and it’s coming back to haunt me.

I take another look at it next weekend. Out of time today.

 

Sounds like too much timing below 2000 rpm at md-high load. Check the timing first. Has the ecm ever been tuned/aftermarket chip? Check the label on the eprom for the broadcast code.

Here's an example spark table from BUB which is an 86 4+3 bin for reference. Low rpm high load timing looks rather aggressive to me.

TABLE: Spark Advance Table

RPM Load Variable LV8
32 48 64 80 96 112 128 144 160 176 192 208
4800 47.11 47.11 45.35 45.35 45.35 41.13 37.27 37.27 33.05 32.34 32.34 32.34
4400 47.11 47.11 45.35 45.35 45.35 41.13 37.27 37.27 33.05 30.59 30.59 30.59
4000 47.11 47.11 45.35 45.35 45.35 41.13 37.27 34.10 33.05 29.88 29.88 29.88
3600 47.11 47.11 45.35 45.35 40.08 37.97 35.51 34.10 33.05 29.88 29.88 29.88
3200 47.11 47.11 43.95 42.89 37.97 37.97 35.16 34.10 33.05 29.88 29.88 29.88
2800 42.19 42.19 40.78 40.43 37.97 37.97 35.16 34.10 33.05 29.88 29.88 29.88
2400 40.78 40.78 40.08 37.97 36.91 35.86 35.16 34.10 32.34 28.48 28.48 28.48
2200 39.38 39.38 39.02 36.91 35.86 35.86 34.45 33.05 30.94 27.42 27.42 27.42
2000 38.32 38.32 37.97 36.56 35.86 34.81 33.40 32.70 29.88 26.37 26.37 26.37
1800 37.27 37.27 36.91 35.86 35.16 34.45 32.70 31.99 28.48 25.66 25.66 25.66
1600 35.86 35.86 35.51 34.45 33.75 33.05 31.99 30.94 27.07 24.61 24.61 24.61
1400 30.94 30.94 30.94 30.94 30.94 28.48 25.66 25.66 25.66 22.85 22.85 22.85
1200 29.88 29.88 29.88 29.88 29.88 27.42 24.61 24.61 24.61 21.09 21.09 21.09
1000 28.13 28.13 28.13 28.13 28.13 25.66 22.85 22.85 22.85 20.74 20.74 20.74
800 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04
600 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04
400 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04 20.04

 

After:
- check oil level of OD and checking mounts
- getting an ODB1 code reader and reading code 34 - and testing for relay vs MAF failure (suspect relays and will replace.
- checking the timing
- visual inspection of MAF (appears new)

No change.

Though what the heck, I’ll make sure all connections on the dizzy are tight. Tight.
Then I notice #8 plug wire is dangling on the upper upper suspension. How it came out, I have no idea.

Plugged it in, everything better than new.

Thanks for all the help! Got up close and personal with my 86 (which has been the red haired step child of the fleet) and I am better for it!

But a simple visual to start would have solved everything.