Bad vibration from motor and/or tranny

[RockyMBronco69]

hello i am in the process of buying a 76 bronco that runs and drives for $3,200 please comment if that seems fair but after this explaination of the problem with it. I already have a 69 bronco sport uncut that i am currently restoring from the ground up a lot of rust! ha. I am new to this blogging but find the posts very helpful.

It has a horrible vibration at idle and gets worse as the rpm's increase. it also has a clank noise at start-up like something is knocking against the bell housing and does it when reved high. Its is believed to have had the engine replaced at some point with an early 80's 302 which might have something to do with this?? I'm at a loss and would like some help!! Thanks!

JR

 

[Bully Bob]

Hi Rocky.., welcome..!

Hard to say W/O a bunch-o-pics.  However.., at $3,200 you could put 10K in it & still be right side up..!! /

From that discription, it sounds like a motor rebuild is in order.  Pull off 1 plug wire at a time..., the roughness will increase with each, until you fihd the one that has no affect on the roughness. That will be the bad cylinder/rod/piston, etc.

 

[Rons beast]

Hey Rock, Welcome.

Ditto all that Bully said, and if pulling 1 wire at a time doesn't isolate the offending cylinder, you may have an unbalanced flywheel/ flexplate.  I have encountered engine swaps that cause a mismatch between the balance. Some engines are balanced neutral, ( without flywheel/ flexplate.) some are only balanced with the flywheel/ flexplate attached.

Research into the year and size of the engine would be needed to find what balance method that engine has.

Good Luck

 

[RockyMBronco69]

Hi Rocky.., welcome..!

Hard to say W/O a bunch-o-pics.  However.., at $3,200 you could put 10K in it & still be right side up..!! /

From that discription, it sounds like a motor rebuild is in order.  Pull off 1 plug wire at a time..., the roughness will increase with each, until you fihd the one that has no affect on the roughness. That will be the bad cylinder/rod/piston, etc.

ok will do thanks! never thought it could be a misfiring cylinder good idea! i'm goin to look at it again tonight so i will add that to my list of tactics.

Thanks,

JR

 

[RockyMBronco69]

Hey Rock, Welcome.

Ditto all that Bully said, and if pulling 1 wire at a time doesn't isolate the offending cylinder, you may have an unbalanced flywheel/ flexplate.  I have encountered engine swaps that cause a mismatch between the balance. Some engines are balanced neutral, ( without flywheel/ flexplate.) some are only balanced with the flywheel/ flexplate attached.

Research into the year and size of the engine would be needed to find what balance method that engine has.

Good Luck

hey Ron,

I was told this several times from a few old timers and my uncle and i believe i'm leaning more towards this idea also. The swap was to an early 80"s 302 and i am thinking that the flywheels didnt get swapped out, and instead of a 50, it got a 20 or vise versa!?

 

[Bully Bob]

The next Question would be;

Is the 76 auto or stick...?  Was the 80's eng. removed fr. an auto or stick.?

If both were autos.., it should be OK .  If the flexplate didn't come with the eng., then it's likely the wrong one was picked up somewhere & bolted on.

As suspected., (auto trans) engine, flexplate, # of teeth, & starter all have to be matched. 

(same for the manual trans..., flywheel & starter.)

 

[RockyMBronco69]

The next Question would be;

Is the 76 auto or stick...?  Was the 80's eng. removed fr. an auto or stick.?

If both were autos.., it should be OK .  If the flexplate didn't come with the eng., then it's likely the wrong one was picked up somewhere & bolted on.

As suspected., (auto trans) engine, flexplate, # of teeth, & starter all have to be matched. 

(same for the manual trans..., flywheel & starter.)

Yes exactly! i have been looking into that also I believe i'm buying it today so i'm just going to take a chance and get it back to my shop and tear into it and see what i can come up with....it can be any of those thing that we have all discussed the guy i'm buyin it from is bein a bit pushy and unhelpful in allowing me to look into it or find anything by digging deeper but i don't think it is goin to be somethin i cant fix with a little time, thought, and elbow grease it shifts smooth and the motor runs strong it's just the highly noticable shake and vibration where the two meet.

Thank you for all of your information though guys and i will let you know what i find!

..................Oh i forgot to mention we started and ran it a few days ago and i discovered that there is a bolt or nut or some type of metal chunk that is in the bell housing that gets into the flywheel and grinds and clangs then gets shot back deeper and eventually falls back into the flywheel and makes more noise untill its kicked back again!! What could this possibly mean???? could a bolt missing outta the fly wheel be causing the shake and being out of balance??

 

[RockyMBronco69]

...Thank you for all of your information though guys and i will let you know what i find!

..................Oh i forgot to mention we started and ran it a few days ago and i discovered that there is a bolt or nut or some type of metal chunk that is in the bell housing that gets into the flywheel and grinds and clangs then gets shot back deeper and eventually falls back into the flywheel and makes more noise untill its kicked back again!! What could this possibly mean???? could a bolt missing outta the fly wheel be causing the shake and being out of balance??

 

[Rons beast]

Hey Rocky,

A missing bolt could cause a vibration.  Do you have an automatic, or manual tranny there?  If auto, that bolt could be allowing the flexplate ( flywheel on an Auto tranny) to flex and it could be cracked now.  A really good inspection is in order.

Good Luck

 

[RockyMBronco69]

Hey Rocky,

A missing bolt could cause a vibration. Do you have an automatic, or manual tranny there? If auto, that bolt could be allowing the flexplate ( flywheel on an Auto tranny) to flex and it could be cracked now. A really good inspection is in order.

Good Luck

Hey Ron,
Yes there is, cant wait to get it in the ole shop and get it figured out

thanks

 

[RockyMBronco69]

Hey guys,

I have another question being that its a C4 auto tranny on this 76, If the flexplate is broken/cracked/or just the wrong one, How hard is it to take off and replace or fix this problem???

Thanks

Jordan

 

[RockyMBronco69]

Hey guys,

I have another question being that its a C4 auto tranny on this 76, If the flexplate is broken/cracked/or just the wrong one, How hard is it to take off and replace or fix this problem???

Thanks

Jordan

..........And also how do i find out what tooth i need and weight??

 

[Bully Bob]

Well.., you have to pull either the eng., or trans/transfer to get to it.

You might be able to have a look-see up thru the inspection plate for some obvious problem.

Would be nice to know thats the prob. B/4 pulling these major components.

"...how do i find out what tooth i need and weight??"

This can be determined by the engine # on the block. (just above/right of starter)

-OR- maybe the intake manifold.., if it's stock/orig.

 

[Bloodwulf]

Just another thought...

Check the motor mounts. A clunk at startup could be a mount with rotted out rubber smacking into the frame. And with no rubber, it obviously wont do much to dampen vibrations from the motor.

Could also check the dampener. When I pulled my motor apart, the dampener was nearly ready to separate. If this has happened to yours, then your balance could be out.

 

[Bully Bob]

WOW..!

Excellent point Bloodwulf makes here..!

I for one forgot all about the harmonic balancer/dampener. (there isn't one on my Ford I-6)

The outer ring is vulcanized on with a layer of rubber.  The rubber can rot out & the outer ring can actually rotate, or in some cases come completely off.

This could be "the" or one of a couple issues causing vibration & noise.  Especially if a motor mount is shot as Bloodwulf pointed out.