Topic: Bad Tranny Noise After Flat Belly

[RynothealbinO]

Ok, so I put a flat belly on my '84 4Runner a couple of weeks ago and now the tranny is making a bad noise.  First or all, I know the speedo cable broke shortly after because it was flexed too much, so I cut it off right where it meets the tranny, so I am wondering if it could be that gear?  Anyways, it only happens above 35 mph or so when I push in the clutch or let off the gas slightly.  If I am on the gas or using the engine for braking it is fine.  So what do you guys think? 

[fordh8r]

Did you change the centerline angle of the drivetrain when you did the flatbelly? How is your joint angle at the rear of the T-case? More info or pics might be helpful here. 

[RynothealbinO [OP]]

I don't think the center line got changed, maybe by 1/8" or so, I don't recall exacly how much but I know I measured it so apparenly it wasnt off enought to get me worried.  There is no lift on the truck, so the driveline angle is a little steeper, but again, not enough to worry about.  Also, if it makes a difference, i did not change the front mounts.  I just had the driveshaft out to replace the rear joint, and the front one seemed fine.  The noise seems to come from about where the speedo cable is as far as front to back goes.  It sounds like there is an idler or  something slapping around with no tension on it.  Not a schreeching noise at all, but not quite a grinding either.  Does that help any? 

[BigMike]

Did you only add skids, or did you actually raise your drivetrain to achieve a true flat belly?

If you raised your drivetrain, could you explain how it is mounted to the frame?

If you have too rigid a mount between your drivetrain and frame, then normal vibrations that before were silent will now be very apparent throughout the entire truck.

And also, if you raised the drivetrain a lot, then you have altered your driveline angle, and it is very likely the vibrations you notice now are coming from a steep rear driveline angle.

Good luck
Mike

[RN37DD]

is there anyway the tranny might be touching the cab? i had that happen when i put an l52 in my 79 and it sounds real bad. i bent the sheetmetal of the tranny tunnel out of the way and the noise was gone.

[RynothealbinO [OP]]

It is a true flat belly, mad out of a 3/8" plate.  It is mounted just like the stock ones and how budbuilt are, all in the stock locations, using the stock center mount.  It could be sheetmetal, but I cut the whole tranny tunnel out and built a new one, so I hope not.  It is rubbing somewhere because thare is an occasional squeking niose.  I am really tempted to pull out the speedo gear and gring of the teeth so it doesnt contact anymore and see if that helps.  I will get to look at it tonight or tomorrow, but I am also rebuilding and trussing my front axle and doing the brakes, so we will see what time allows.

[MiniSimp]

Your pinion angles are probably fawked.
Unless you lifted the engine as well.....

[Rocksurfer]

Your pinion angles are probably fawked.
Unless you lifted the engine as well.....

  If you didn't lift the engine it will tip the rear output up and mess with it even if you tip the 3rd up.

[fordh8r]

Your pinion angles are probably floped.
Unless you lifted the engine as well.....

  If you didn't lift the engine it will tip the rear output up and mess with it even if you tip the 3rd up.

That's what I was trying to get at, but it sounds like that may not be his issue.    He says an occasional squeak also. Sheetmetal contact?    How about some pics? Maybe that could help. 

[RynothealbinO [OP]]

Well, I blocked the rear end up and had my dad run it through the gears at normal operating speeds while I went underneath.  I am pretty sure it is coming from the U-joint, or from the very rear of the tranfer case.  Everything seemed tight and the joint was recently greased, but my dad said it sounded like a U-joint that was flexing too much.  With the rear tires off the ground the noise  was way worse and you could really feel the truck vibrate from the shaft.  So I geuss that would explain why it only did it with no load, I geuss if it was under load it would take out any extra slop or vibration.  So now the question is how do I fix this.  Should I raise the front mounts and hope that takes care of it, or is there something (think cheap if possible) that can be done with the drive shaft?  If I get time tomorrow I am going to get longer mount bolts and temporarily drop the crossember an inch or two to see if that helps, but I really would like to get this sorted out properly so it can stay flat.  Thank you guys for the help.  Any more ideas?

[MiniSimp]

You either have to lower the transfer case mount, or raise the engine mount.
That's pretty much your only choices.

[TheCookieMonster]

You either have to lower the transfer case mount, or raise the engine mount.
That's pretty much your only choices.

 ...i flatbellied my truck without raising the motor mounts and im getting the same noises. a buddy of mine called marlin and talked to Mike and he said its the back t-case. the case has to be level or its not getting proper oil circulation. the oil slinger is in the back of the case so if the front of the case is lower than the rear then there is gonna be problems. im just gonna lift my motor til its level again. i wouldnt run your truck on the road til its fixed or your gonna kill your t-case bearings 

[fordh8r]

You either have to lower the transfer case mount, or raise the engine mount.
That's pretty much your only choices.

...i flatbellied my truck without raising the motor mounts and im getting the same noises. a buddy of mine called marlin and talked to Mike and he said its the back t-case. the case has to be level or its not getting proper oil circulation. the oil slinger is in the back of the case so if the front of the case is lower than the rear then there is gonna be problems. im just gonna lift my motor til its level again. i wouldnt run your truck on the road til its fixed or your gonna kill your t-case bearings 

 

Also, don't just raise the engine  . Measure the angle of the drive flange on the 3rd member then raise the engine till the t-case flange is withing 1* of that same angle.  I got mine within 1* when I did my custom X-member and it runs like new. Not a single vibe, even up to *cough* ...80mph...*cough* cough*....

At this point I trust the driveline at that speed more than I trust the tires. 

[TheCookieMonster]

Also, don't just raise the engine  . Measure the angle of the drive flange on the 3rd member then raise the engine till the t-case flange is withing 1* of that same angle.  I got mine within 1* when I did my custom X-member and it runs like new. Not a single vibe, even up to *cough* ...80mph...*cough* cough*....

At this point I trust the driveline at that speed more than I trust the tires. 

thats good to know. thanks for the good info fordh8r  ....i wish i would have known all of this before i did all that work 

[fordh8r]

thats good to know. thanks for the good info fordh8r  ....i wish i would have known all of this before i did all that work 

Think of it this way....you were only halfway done.    So, nothing lost, right? 

[TheCookieMonster]

Think of it this way....you were only halfway done.    So, nothing lost, right? 

true...i just need to finish 

[All_Set]

If it's an oiling issue, could you add more oil?  Is the driveline still in phase?

Would a double cardan work well enough with that angle? 

Please report back with your fix!

[RynothealbinO [OP]]

Well, I didn't get a chance look into the problem at all today.  Instead I ignored it and rebuilt my front axle instead...well one side so far anyways...and I have one side torn apart.  I can't wat to try out the vented rotors and bigger master cylinder and having rear brakes because they apparently need to be bled really bad.  Anyways, I am going to raise the front mounts and possibly shim the rear axle to get the joints to the right angles in relationship to each other, but I am toying with the idea of going with a CV style shaft...but there is no money to do that right now.  I am hesitant to raise the front end because my front shaft is already unhappy.  I used to be able to leave it locked in and never even notice, now it howls really bad above 30 or so, but maybe that would be the tranfer case.  I am thinking about just leaving it for now and finishing out the next three weeks of summer hoping nothing goes wrong, which should work because it only gets driven 5 miles a day.  Then I am going off to school where I will hopefully have an on campus job, so I would probably only use the truck once or so a week...so at that point I am paying $25 in insurance on that single trip when I just as easily could have gotten a ride.  So with no car I actually save money and have some to do this all properly next summer.  But in the mean time I will keep you guys posted as to what I do with it or if something alse goes wrong.

[Stinson]

Dont raise the motor, thats only goint to raise your COG more.  Put a CV shaft in the rear, and rotate your rear pinion up to point at the output on the T case.

[beyondlogic]

how would you raise the engine to level it off. 

[TheCookieMonster]

how would you raise the engine to level it off. 

make taller motor mounts, and put them in to raise the engine