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  #1  
Old 02-12-2014, 03:17 PM
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Heimeken Heimeken is offline
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Engine Transmission Vibration

Need some advice. I did a complete drivetrain swap on my 78 J10. It originally had the TH400 and Quadratrac. I put in a 727 and NP208 along with J20 axles. The 727 came out of an 85 wagoneer, I drove it before taking it out and it ran smooth.

What I am getting is a bad vibration around 2K rpms and just gets worse as you rev it. I already eliminated the rear end and driveshaft, even the transfercase is now removed and It still vibrates on any gear, even park and neutral.

Flexplate is the same one that was on the 727 before and it was also on a 360, but it sure feels like a balancing issue. 727 shifts nicely. And yes I removed the pilot bushing behind the crank shaft. New engine and transmission mounts too.

I'm running out of ideas...
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Last edited by Heimeken : 02-12-2014 at 03:41 PM.
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  #2  
Old 02-12-2014, 04:13 PM
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Flexplate on backwards?
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  #3  
Old 02-13-2014, 12:36 PM
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Chevelleguy Chevelleguy is offline
 
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Can you unbolt the converter from the flexplate and push it back into the transmission so that you can run the engine and see if it vibrates all by itself? I seem to recall that's not possible, so you may have to take the tranny loose to isolate the problem.
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  #4  
Old 02-13-2014, 12:52 PM
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Tinkerjeep Tinkerjeep is offline
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How would one install the flexplate backwards? The crank-flange bolt holes are drilled in a specific offset bolt-circle to prevent this.

TF727 - the TC could be bad, is it lock-up?

The flexplate could be cracked.

The crank damper may be loose.

I never was enamored with the puny, fine-thread flex-plate bolts Chrysler used. I stripped a few threads off one of mine when installing the TC in my 81 Cherokee. It got lock-tited. Maybe you lost one or two bolts due to stripped threads or sheered heads? I lost 2 of my 3 TH400 flex-plate bolts on a back and forth trip to work in a "nearby" town after mistakenly using motor-mount bolts for flex-plate bolts in the recent engine rebuild. The bolts I used sheered the heads one at a time and that made some noise that scared the feces out of me. Especially 70 miles from home. I parked it infront of the house I was working on and crawled underneath. I had one Flexplate bolt in place, and had driven with one broken for around 100 miles and the second loose for about 40 miles.

What engine is this bolted to? A 401 requires a different flex-plate than a 360. There is a weight welded to the 401 plate. No weight on the 360 plate. The wrong plate would make a vibration noticeable in all gears from around 2,000rpm and up, worsening the higher the revs climb.

AND this is TH400 flexplates. There was never a 401 and TF727 in a factory Jeep. In an AMC car, perhaps. The TF727 was introduced to AMC cars in 1972. The 401 was used from 1971 to 1973/4 in AMC cars. But I have never seen one in person.

Last edited by Tinkerjeep : 02-13-2014 at 01:18 PM.
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  #5  
Old 02-13-2014, 12:59 PM
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babywag babywag is offline
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Sounds like a flexplate balance issue.

Since the problem came with the swap...
Only thing you can really try is a different flexplate?
Or maybe have the imbalance of them(th400 & 727) checked, and see if they match.

Maybe the 727 flexplate was balanced specifically for the other engine on a rebuild?

No way to mount a starter w/o some form of bell bolted to an AMC AFAIK, so I don't think you could run it in the truck by itself?
Unless you're creative and can make a starter mount somehow.
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  #6  
Old 02-13-2014, 01:12 PM
Ristow Ristow is offline
 
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Quote:
Originally Posted by Carnuck
Flexplate on backwards?

you can't do that.
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  #7  
Old 02-13-2014, 01:13 PM
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Quote:
Originally Posted by babywag
No way to mount a starter w/o some form of bell bolted to an AMC AFAIK, so I don't think you could run it in the truck by itself?
Unless you're creative and can make a starter mount somehow.

The starter mounts to the tranny, so you are correct.
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  #8  
Old 02-13-2014, 01:15 PM
Ristow Ristow is offline
 
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Quote:
Originally Posted by Chevelleguy
Can you unbolt the converter from the flexplate and push it back into the transmission so that you can run the engine and see if it vibrates all by itself? I seem to recall that's not possible, so you may have to take the tranny loose to isolate the problem.


the 727 will hit the weight on the converter,so correct,you don't want to do that.
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I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!


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  #9  
Old 02-13-2014, 01:26 PM
Ristow Ristow is offline
 
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your just sure it's not a misfire issue?
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Ristows right.................again,




Quote:
Originally Posted by Fasts79Chief
... like the little 'you know what's' that you are.




Quote:
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I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!


→ Where the kids hang out...

fsjbuilder.org come for the mindless chat,stay for the hand drawn emoticons.

It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...
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  #10  
Old 02-13-2014, 02:02 PM
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Quote:
Originally Posted by Ristow
the 727 will hit the weight on the converter,so correct,you don't want to do that.

Technically he could pull the tranny, remove the TC and remount the tranny to allow him to bolt on the starter and then he could run the engine to isolate the vibes. A lotta work though.

Cool thing about AMC TF727s and Flex-plates/TCs...you can't do this in a Dodge. The ring-gear is welded to the TC!
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  #11  
Old 02-13-2014, 03:12 PM
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serehill serehill is offline
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Yeah

Process of elimination does it vibrate in the driveway at High rpm in neutral or just driving down the road. What about the harmonic balance is it original?
If it won't do it in the driveway it isn't the flex plate or engine balance.
If both engines were 360's the flex plate balance shouldn't be the issue. Have you pulled the inspection plate to see if the flex plate may have gotten bent? Start it up & watch the plate.
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  #12  
Old 02-13-2014, 03:16 PM
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Quote:
Originally Posted by serehill
Process of elimination does it vibrate in the driveway at High rpm in neutral or just driving down the road. What about the harmonic balance is it original?
If it won't do it in the driveway it isn't the flex plate or engine balance.
If both engines were 360's the flex plate balance shouldn't be the issue. Have you pulled the inspection plate to see if the flex plate may have gotten bent? Start it up & watch the plate.

"It still vibrates on any gear, even park and neutral." 1st post...
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Old 02-13-2014, 04:10 PM
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In another thread here a shop claimed the guy's flexplate was on backwards. Maybe it was replaced by the previous owner who gave up after the vibration?
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  #14  
Old 02-13-2014, 04:20 PM
Ristow Ristow is offline
 
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that was on the nail head tranny carnuck,which can be put on backwards due to spacer on the crank. the 727 flexplate will interfere the block if backwards. also the starter bendix would be jammed into the ring gear with no way to disengage.
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I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!


→ Where the kids hang out...

fsjbuilder.org come for the mindless chat,stay for the hand drawn emoticons.

It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...
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  #15  
Old 02-13-2014, 04:30 PM
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Tinkerjeep Tinkerjeep is offline
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Quote:
Originally Posted by Carnuck
In another thread here a shop claimed the guy's flexplate was on backwards. Maybe it was replaced by the previous owner who gave up after the vibration?

Quote:
Originally Posted by Ristow
that was on the nail head tranny carnuck,which can be put on backwards due to spacer on the crank. the 727 flexplate will interfere the block if backwards. also the starter bendix would be jammed into the ring gear with no way to disengage.


Okay. But I know for a fact AMC V8 -to AMC-TH400 flexplates cannot be bolted on backwards. I suspect the bolt pattern on the crank is the same from 1973 up to 1991, because any of those year's cranks can be bolted to any of those year flexplates. Pre 73 or 72 AMC V8 Crank flanges were different.
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  #16  
Old 02-13-2014, 05:27 PM
Ristow Ristow is offline
 
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i don't know if the bolt pattern prevents the flexplate from being reversed. i do know it will interfere the block,and thus can't be done.
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Originally Posted by Hankrod
Ristows right.................again,




Quote:
Originally Posted by Fasts79Chief
... like the little 'you know what's' that you are.




Quote:
Originally Posted by Fasts79Chief
I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!


→ Where the kids hang out...

fsjbuilder.org come for the mindless chat,stay for the hand drawn emoticons.

It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...
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  #17  
Old 02-13-2014, 06:59 PM
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Tinkerjeep Tinkerjeep is offline
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yeah, the bolt holes are offset drilled so the flexplate will only bolt up in one position, other wise all 6 bolt holes will not align. Its likewise impossible to flip the flexplate and bolt it on because the 6 bolt-holes will not all align. Try it.
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  #18  
Old 02-13-2014, 07:52 PM
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What about the harmonic balancer..I've never had one do it but have heard of them becoming unglued and slipping position.

J20
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  #19  
Old 02-13-2014, 07:52 PM
Ristow Ristow is offline
 
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oh i believe it,makes sense for sure. just never tried it myself.
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Originally Posted by Hankrod
Ristows right.................again,




Quote:
Originally Posted by Fasts79Chief
... like the little 'you know what's' that you are.




Quote:
Originally Posted by Fasts79Chief
I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!


→ Where the kids hang out...

fsjbuilder.org come for the mindless chat,stay for the hand drawn emoticons.

It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...
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  #20  
Old 02-14-2014, 11:06 AM
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Tinkerjeep Tinkerjeep is offline
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Quote:
Originally Posted by Ristow
oh i believe it,makes sense for sure. just never tried it myself.

I did. Wondered if it was possible. Its not.

Quote:
Originally Posted by J20 project
What about the harmonic balancer..I've never had one do it but have heard of them becoming unglued and slipping position.

J20

I have heard of this too. Of the 6 dampers I have sitting on my work-room floor, 2 have the rubber bulging, one has it pushed out badly. Strangley enough: the worst one has the timing mark still closely aligned to the crank key-way! I admit, I mentioned the crank-damper (harmonic balancer) being loose, but forgot about the seperation issue. I would have to say: check it! Its kind of a last ditch effort to try to find something that is capable of causing engine vibes and he didn't say he did anything to the damper/balancer, so its unlikely, but its not IMPOSSIBLE.

Last edited by Tinkerjeep : 02-14-2014 at 11:14 AM.
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