low rpm shake diagnosis

[mat in tn]

i figured i would open up a discussion to the panel of experts and novices alike. one of the most common things I end up doing is "problem solving". been doing it for years. sometimes it's more like hunting season though where you try everything yet never get a sight of your quarry.
we just finished an install on my friends 94 f150 4wd. it's a truck he has been driving hard along with teaching both kids to drive and frankly it's a real testament to "built ford tough"! Anyway, he rebuilt a 5.8 to replace a 5.8. and it runs and he has been driving it, but it has a "shake". idle to about 1200. bad enough that its now leaking from the rear main. now before anyone yells at me. haha. I know these don't heal! not my truck, not my build. just thinking over a diagnosis and willing to help him.
I have been theorizing on my own about possible causes. harmonic balancer, flex plate etc.
new balancer but original flex plate. Replaced transmission a year ago. third one! the second was only in doing 4wd conversion. originally a 2wd truck.
it happens at idle in neutral also so to me that removes all but the torque converter/flex plate. how common is torque converter balance problem with an e4od? just because I have not dealt with it does not mean others haven't. again, I'm looking for other experiences and opinions. any item which spins must be balanced and the more you bolt together the more you must balance the whole assembly.

[grumpin]

My 92 Bronco is a 5.8 and E4OD. I had an E4OD behind a 460. Never had them apart, no vibes or shaking.

Because it was rebuilt the first thing that popped into my head was a bad lifter, sticky, stuck, collapsed. You would have heard it ticking if it was collapsed.

Or a stuck valve. If it wasn’t shaking before the rebuild and is now, I would assume it’s the engine.

Harmonic balancer as you mentioned.

I may be off base, but what I thought of.

[mat in tn]

after talking this over he says it's been shaking for a long time but it's much worse now since changing engines. I could not get him nailed down on whether it has been happening since the latest trans was installed or whether it is the original torque converter. but I'm trying to diagnose rather than just deciding. I believe it has been replaced but not sure

[mat in tn]

one more thing. we did run the engine for quite some time on an engine run stand. up to temp a few times tuning and timing etc. no indication of any vibration etc . and solid mounts. should have been even more noticeable that way. run without torque converter on run stand.  

[grumpin]

Oh, ok. Motor mounts, tranny mount?

[mat in tn]

all mounts good and even replaced the transmission mount in the process to be sure

[grumpin]

This will drive a person nuts!

[mat in tn]

oh he is there! haha

[1986F150Six]

Did you confirm that the torque convertor had been replaced?

[grumpin]

Since things around the motor have been checked. Maybe the driveshaft or rear end. Wheel bearings. Brakes.

[85lebaront2]

Can you get a strobe like that you can adjust the flash speed on? If you can, then from underneath work on "freezing" the up and down motion and look at the location of (a) the balancer, (b) the torque converter/flex plate (put paint on 3 of the 4 nuts so they are identifiable with the strobe). Run it to the worst vibration with the plastic converter drain access plug and torque converter nut access plate removed. Hopefully you will find the heavy spot. Once you find it, use some long bolts so you can slide the E4OD back far enough to rotate the torque converter. Take the nuts off first and shove it back, once you have enough clearance, rotate the converter one half turn, reassemble and repeat the previous test. If the vibration is gone or changes one way or the other (more or less shake) you have found the problem. If the shake is either opposite or the same as the flexplate weight, then that weight is wrong, too heavy it will be down when the back of the engine is down, too light and it will be up.

[mat in tn]

very interesting method. I will suggest that, but I think he is going with a new plate and converter for peace of mind. I say that a little "tongue in cheek". I don't like shot gunning parts at a problem. I want to learn from challenges not just get rid of problems.

[85lebaront2]

Make sure it is the correct weight and while it is being changed, drain the converter so the front trans seal can be changed, check for play in the pump bushing and slop in the end of the crank where the torque converter snout fits.

I also like to learn from problems, not just throw parts at it until one solves it.

[mat in tn]

that's the best part of changing one thing at a time and test.  but for pulling the trans I say plate with converter and new seal because you are staring at it.
 I know that it seems like grasping at straws but "debris". follow along. if one pulled the trans pan and found very much debris, how likely is it that similar debris could have settled out of the fluid in the converter? let's say for example that you had a gallon of old fluid in a jug, and it sat for a year. you pour it out slowly and notice a gray film in the bottom of the jug. how likely is it that a clump/ clot of settlement is in the converter weighting it? theoretical question only.
this comes to mind from having done flushes and the catch pan/canister seemed to accumulate such debris and it was necessary to scrape it out. it clung like peanut butter! and it was what settled out of clean fluid.

[85lebaront2]

One thing, centrifugal force. Once the engine is spinning the heaviest stuff goes to the outside. How else would you get the air out?

[FuzzFace2]

mat in tn wrote

one more thing. we did run the engine for quite some time on an engine run stand. up to temp a few times tuning and timing etc. no indication of any vibration etc . and solid mounts. should have been even more noticeable that way. run without torque converter on run stand.

To me that points to the converter as it was not bolted to the flex plate and spinning when the motor was running on the stand.

I think it was said to move the trans & converter back some and run and see if it dose it with motor bolted in the truck.

Bill said to move them back, rotate the converter 1/4 or 1/2 turn and bolt it back up but I dont think you can do that if it has a drain plug as the flex plate had a hole for it to pass through.
I dont get the strobe thing & movement but maybe if I seen it I would

I forget when did this start, new motor or trans?
Then again it ran smooth on the stand and no converter ...........
Dave ----

[85lebaront2]

Dave, on my flex plate there are two openings for a drain plug for the C6 converter. The E4OD converter has the drain plug on the outer diameter which is the reason for the plastic access plug in the bottom of the converter housing.

The strobe light is not a fixed frequency flash, but one you can vary in order to "freeze" a motion or a spinning object. I borrowed one from the lab I worked in many years ago to set the max rpm on a BMC 2.2 Litre High Speed Diesel in a London Taxi. Engine was a copy of a Daimler-Benz 1.9L push rod valve Diesel and had a Lucas injection pump that was a copy of the Bosch one. They are very useful in finding a periodic noise or shake.

[mat in tn]

yes, it seems that the plug itself will act as a weight to throw it off balance that's why it must have it installed when the whole gets balanced, but that's not really in the field. most flex plates i have used have four drain accesses also. one beside each mounting hole about 1-1/2 away if someone changes the drain plug to a different weight one that can mess with things for sure

[85lebaront2]

Mat, many of the factory ones I have seen are a hollow pipe thread with a hex head. Chrysler used to use a tiny one and GM was too cheap to use one after the demise of the dual coupling Hydra-Matic.

[Rusty_S85]

FuzzFace2 wrote

mat in tn wrote

one more thing. we did run the engine for quite some time on an engine run stand. up to temp a few times tuning and timing etc. no indication of any vibration etc . and solid mounts. should have been even more noticeable that way. run without torque converter on run stand.

To me that points to the converter as it was not bolted to the flex plate and spinning when the motor was running on the stand.

I think it was said to move the trans & converter back some and run and see if it dose it with motor bolted in the truck.

Bill said to move them back, rotate the converter 1/4 or 1/2 turn and bolt it back up but I dont think you can do that if it has a drain plug as the flex plate had a hole for it to pass through.
I dont get the strobe thing & movement but maybe if I seen it I would

I forget when did this start, new motor or trans?
Then again it ran smooth on the stand and no converter ...........
Dave ----

On my OE flex plate there is only the ability to flip the converter 180* (1/2 turn) not 90* (1/4 turn) but my SFI replacement flexplate I bought how ever has drain openings on every corner that will allow for a 90* (1/4 turn).  I thought that was nice for the aftermarket replacement flexplate to have that cause the OE one made it a pain as you had to get it exactly right where this one I have now doesnt matter just line the studs up and you are good as there is an access hole for the drain plug in every position.