Zf5 Shake? Help!

[J_For_JUstin]

Hey guys hopefully someone can give me there opinion on this. I have a 1994 7.3 idit zf5 I have been chasing this problem for over a year now. So over a year ago my transmission crossmember rusted and broke, causing the transmission to sit freely. Which in turn caused the rear case of the transmission to crack. The truck would shake really badly on clutch engagement. So I took it out rebuilt it, welded the crack. Seemed like it worked at first, then it cracked right next to the weld. The symptoms came back.
Fed up with it, it sat for 6 months. Now I sourced a transmission put it in, no shake for about 20 miles. Then it started shaking on clutch engagement again you can really tell in 1st and reverse. It seems to get worse as you drive it, when the clutch/ drivetrain has warmed up. Clutch looks how it should. I have luk single mass flywheel 2 years ago too. Engine mounts? But it isn't as bad when it's cold? Can the rubber heat up in the mounts and become softer causing it to be worse when hot or is that just not the case? It's my last guess but I sure don't want to pull my truck apart and the pull out the engine to do the mounts only for it not to be the problem... Any suggestions would be greatly appreciated before I light it on fire.

 

[Big Bart]

Take my advice with a grain of salt as I have a C6 but not a ZF5. However I have had manual vehicles before, and I have done several clutches.

Keep in mind your
1) Flywheel, clutch, pressure plate, and throwout bearing are a seperate system.
2) Your clutch pedal, master cylinder, and slave cylinder are a sperate system.
3) Your tranny is a seperate system.
4) Your drive shaft is a seperate system.
5) Your axle is a seperate system.


So try to isolate the issue, but remember it can be mutliple systems working together to cause the issue or a return of the issue. So look at all but I am guessing it is simply damage to the clutch system from the prior issues. (Once you have irregular wear on a clutch, replacement is generally the only way to fix it.)

You have shared
1) Your motor mounts may be compromised. You should think about replacing especially if the tranny is already coming loose. May be easier to do it with the tranny on, but you will be loosing the tranny mount and that may help.
2) You did not share, is your tranny cross member now replaced with a factory one or something you created/fabricated. (If fabricated, would suggest replacing with factory. Just take that out of the equation.)
3) You have a 2 year old LUK flywheel and hopefully a new LUK pressure plate and clutch went in at the same time. (Also did you clean the flywheel free of its protective coating?? If not that might be adding to your wows.)
4) That you have shifting issues twice. 1) Upon loosing your crossmember. 2) When your tranny cracked again.
5) Clutch works till it gets warm and starts to act up.

Other thoughts - (Could exasterbate your issues.)
1) How is the driveshaft? Good u-joints and good center support bearing?
2) How is your axle? Does it spin easily, do you have a lot of play in the pinnion and ring?
3) How is your clutch hydraulic system.
4) Does your engine move side to side when taking off in 1st/reverse gear. If your clutch is fighting the engine or tranny moving around, to your point this could ampliy the issue. However would guess it would happen cold or hot.

What I would do at this point -
1) I would confirm via inspection and lubricating that the clutch pedal, slave, and throwout bearing arm (If possible) all move gracefully and do not stick. It could be as simple as your clutch pedal, master, slave, or arm is causing the issue by not moving evenly/gracefully.
2) Check your axle and look for issues with the driveshaft. (Bad u-joints or center support bearing causing the tranny to wrestle with it.)
3) After confirming the above I would pull the tranny and -
a) Replace the clutch, pressure plate, and throwout bearing. It could be as simple as the clutch was bad and the springs or the center spline hole were not machined right. However its a good brand so sounds like these got damaged from the first two tranny issues. Now they likely have uneven wear, chadder markes, burn marks, or other damage from prior issues.
b) Resurface the flywheel. Always do this when replacing a clutch, its 50% of the clutch surface it uses. Always torque to spec and use blue locktight on the crankshaft/flywheel bolts.
c) Check to the new tranny you put in for input shaft for wear and the bearings for play. Other members if you have experience with a ZF5 please comment on how much play a input shaft should have. I do not know and would like to know.
d) Find out what if any lube you should put on the input shaft and clutch spline hole so it can slide smoothly. (This could cause some studder in releasing the clutch smoothly.)
e) Make sure your throwout bearing arm is lubed if needed and moves freely.

I know that sounds like a lot of work but again my thought is during your tranny issues, when the truck was not working as it should, it caused hot spots, or other anomolies to your clutch, pressure plate, and flywheel. Swapping trannies only fixed the bad housing and cause of the clutch failure, but did not fix the now compromised clutch.

Also check the other threads, I have not heard you have to pull the engine to do the motor mounts. But perhaps you are right, but confirm before you go to all that work.

FYI if you decide to light it on fire please do not use gasoline, the gassers will never let it down you have to use gas to get a Ford moved down the road!

Be sure to let us know what you find out!

 

[J_For_JUstin]

Take my advice with a grain of salt as I have a C6 but not a ZF5. However I have had manual vehicles before, and I have done several clutchs.

Keep in mind your
1) Flywheel, clutch, pressure plate, and throwout bearing are a seperate system.
2) Your clutch pedal, master cylinder, and slave cylinder are a sperate system.
3) Your tranny is a seperate system.
4) Your drive shaft is a seperate system.
5) Your axle is a seperate system.


So try to isolate the issue, but remember it can be mutliple systems can work together to cause the issue or a return of the issue. So look at all but I am guessing it is simply damage to the clutch system from the prior issues.

You have shared
1) Your motor mounts may be compromised. You should think about replacing especially if the tranny is already coming loose. May be easier to do it with the tranny on, but you will be loosing the tranny mount and that may help.
2) You did not share, is your tranny cross member now replaced with a factory one or something you created/fabricated. (If fabricated, would suggest replacing with factory. Just take that out of the equation.
3) You have a 2 year old LUK flywheel and hopefully a new LUK pressure plate and clutch went in at the same time. (Also did you clean the flywheel free of its protective coating?? If not that might be adding to your wows.
4) That you have shifting issues twice. 1) Upon loosing your crossmember. 2) When your tranny cracked again.
5) Clutch works till it gets warm and starts to act up.

Other thoughts - (Could exasterbate your issues.)
1) How is the driveshaft? Good u-joints and good center support bearing?
2) How is your axle? Does it spin easily, do you have a lot of play in the pinnion and ring?
3) How is your clutch hydrolic system.

What I would do at this point.
1) I would confirm via inspection and lubricating that the clutch pedal, slave, and throwout bearing arm all move gracefully and do not stick. It could be as simple as your clutch pedal is causing the issue by not moving evenly/gracefully.
2) Check your axle and look for issues with the driveshaft. (Bad u-joints or center support bearing.)
3) After confirming the above I would pull the tranny and -
a) Replace the clutch, pressure plate, and throwout bearing. It sounds like these got damaged from the first two tranny issues. Now they likely have uneven wear, chadder markes, burn marks, or other damage from prior issues.
b) Resurface the flywheel. Always do this when replacing a clutch. Always torque to spec and use blue locktight on the crankshaft/flywheel bolts.
c) Check to the new tranny you put in for input shaft for wear and the bearings for play. Other members if you have experience with a ZF5 please comment on how much play a input shaft should have. I do not know and would like to know.
d) Find out what if any lube you should put on the input shaft and clutch spline hole so it can slide smoothly. (This could cause some studder in releasing the clutch smoothly.)
e) Make sure your throwout bearing arm is lubed if needed and moves freely.

I know that sounds like a lot of work but again my thought is during your tranny issues, when the truck was not working as it should, it caused hot spots, or other anomolies to your clutch, pressure plate, and flywheel. Swapping trannies only fixed the bad housing and cause of the clutch failure, but did not fix the now compromised clutch.

Also check the other threads, I have not heard you have to pull the engine to do the motor mounts. But perhaps you are right, but confirm before you go to all that work.

Be sure to let us know what you find out!

I must say first thank you for your detailed and extensive response.
1. Slave and master cylinder is new (came pre bled) also has heim joint mod and eliminates any slack the typical pedal bushing would give. I know it has its correct range of motion.
2.Tranny Mount is new, crossmember is replaced with oem, has all the correct braces and is very sturdy now.
3. New rear u joints (no support bearing) it's a single cab.
4.Axle moves freely not sure about play but I doubt it's the issue.
Although the engine mounts sure aren't the best since I'm sure they are factory. I don't THINK they are the issue.
I did slap my phone under the truck to see if I could record what I saw. As I let the clutch out...I saw on my phone recording that the driveshaft was NOT turning smoothly almost like the clutch was grabbing unevenly. Like a warped pressure plate or flywheel or something. I will attach a link to the video

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At this point my best bet is to get the flywheel resurfaced and replaced the clutch/pressure plate. I think you are right about it being damaged from the prior incidents with the crossmember.

 

[Big Bart]

J for Justin,

Awesome video!

Glad you have things ship shape and used a factory tranny support.

I did not see the motor or tranny twisting/moving, but you were taking off lightly. But still would expect some movement if you had a broken engine or tranny mount.

Agree, sucks but you want to fix it, so you have to put in the work. But a stick is easier to pull if that is any consulation.

With that said, before you pull the tranny, I hear something making noise in the video. Sounded like your diff. the first pass then the clutch the second pass. (Like the clutch springs are broke and the clutch is slapping back and forth) Perhaps do a second video and make sure you to go past the tranny and past the diff 3 times. On the fourth get on it to see if the engine or tranny moves. You likely can figure out the noise and rule in or out the drive shaft, diff, or engine and tranny mounts.

Then put the rear axle on jack stands and your tranny in neutral and turn the driveshaft and see if anyting is rough or binding. Wiggle the driveshaft, something looks off when it turns, but could be a sticky or broken clutch or pressure plate. Crank back and forth to check for excessive diff play. (Which could add to the problem.) If anyting seems out of place pull the diff cover, inspect your ring and pinion, spider gears, etc. Metal chuncks at the bottom of the pumpkin are a bad sign. (Fine flakes or small shavings are not likely a issue.) If all is good reseal and refill. (Good to change the fluid every 50K mi anyhow.)

U-joints - It is very easy to screw these up, I am guilty of messing up even after I have done dozens. Very hard to do right without a shop press. It just takes one needle bearing falling into the bottom of the cup when hammering and whammo your done in a few miles. So check them when you check the rear diff.

All is still good then time to pull the tranny and redo the clutch system. As mentioned resurface the flywheel too. If it still chadders after all that let me know, I will order a can of charcol lighter off Amazon and send at no fee!

Also to any others reading, is there any known issues in a ZF5 (Shafts, gears, bearings, etc.) known to cause clutch chadder? Please advise, I am not a ZF5 expert by any stretch.

Send us a couple of videos of what you find!