transmission rattle @ a given RPM

[THeske]

Sorry guys this isn't a Dodge transmission but they work the same,

K heres the problem, when I'm accelerating my transmission starts to rattle in every gear except OD, fourth gear being the worst, the rattle starts about 1600 rpm & quites at about 1850 now thats just about right in the middle of my good power range, 250 rpm of noise it's very very irratating/annoying, The heavier the pull the louder it is, Not a grinding noise but a rattle ( Like the transmission is loading & unloading and giving a gear/bearing slapping rattle)

This truck had a new heavy duty clutch disk/pressure plate put in 6 months ago, the clutch disk is a ceramic button disk with out any dampening springs ( solid disk and hub basically ) Now would this noise be coming from the motor harmonics? and then transfering through the transmission because of the disk having no dampening abilities, and why only at those RPMs,

Oh yea It's a new transmission, 6 months ago also, Fords ZF-547, good for an advertized 470 Lb's torque, about the same as the NP4500

 

[DVolk]

transmission rattel @ a given RPM

Id say its in the t-case , sloppy chain or bearing , but id check the front and rear diffs for lube and excessive heat when driveing awhile feel them to see if there warm the axels its self (houseing )

 

[RustyJC]

One reason sprung discs are used is to dampen torsional vibration. Your engine is passing through a torsional critical speed (a natural harmonic frequency), and the undamped torsional vibrations are rattling the gear teeth (loading and unloading them).



Rusty

 

[THeske]

Thanks Rusty: were thinking the same on this matter, For the life of me I can't remember when this problem developed some time during my clutch altering experences, This is the third pressure plate/disk that was installed in a two month period, Original ford disk the Cummins was spinning the center hub out of the disk stripping the rivets, 2nd larger diameter Ford disk & pressure plate would slip in fourth gear @ WOT, pulling 6000Lb's, For the 3rd clutch, A Clutch shop custom made up a heavy duty pressure plate & this Ceramic non-sprung disk, everthing is Holding up good but now I have this God forsaken rattle,

A few more replys on this matter would be welcome, Before I start pulling clutches again

 

[RustyJC]

Even a sprung disc won't eliminate it completely. My NV5600 with the South Bend CON OFE will growl pretty loudly down around 1800 RPM or below when I'm towing my 5th wheel. One of the Fluidamper harmonic balancers would probably help more, as would a dual mess - oops, I mean dual mass - flywheel! :{



Rusty

 

[THeske]

OK so a replacement harmonic balancer, I can go with that, easier than doing a clutch job, were do I find one for a 5. 9 Cummins application, And how many peso's can I expect to hand out?

 

[driverswanted]

I'm working on this vibration that gets bad at those rpm's and worse under load too. I have a 12" Chevy diesel disc in mine. Also went with the kevlar/nylon pilot bushing. I have the fluidic dampener and it does nothing for this so don't waste your $ on that hoping it will fix it. It does work nicely at calming the low rpm vibrations though. I also thought it was in the transfer case. I had my t-case go bad and the replacement did not improve the vibration. Maybe Imy second t-case is loose too.

Sorry about shooting down so many ideas but I'm really interested in fixing mine too. I'm getting ready to pull my transmission off and look at my pilot. Are you running a bushing or bearing at the pilot? Do you have an adapter plate on your's?

How about an imbalance problem with the disc and pressure plate? Anyone have opinions on that?

I have my rear diferential about 1 degree low. I'm thinking about taking mine to an old driveline troubleshooting expert in March.

 

[RustyJC]

I have the fluidic dampener and it does nothing for this so don't waste your $ that hoping it will fix it.

Guys, nothing is going to completely "fix it" unless you start trying to move the torsional critical speed by changing crankshaft stiffness, rotating mass, etc. That's what the dual mass flywheel does - it reduces the "effective rotating mass" of the flywheel which raises the torsional critical speed. I've just seen some users of the Fluidamper harmonic balancer report some improvement in gear rattle at this speed.



Go drive some other trucks and see how they compare to yours. There's no sense throwing money at a perceived problem that you may find is a normal operating characteristic of these beasts - after all, they are trucks and haven't been subjected to the purging of NVH (noise, vibration and harshness) to the extent that passenger cars go through in their development.



Hey, maybe the "plastic gears" in the G56 won't rattle as badly - how about a transmission swap?? Oo. Oo. (Just kidding... ) :-laf



Rusty

 

[THeske]

I'm running a bearing for the pilot ( New ) When the clutch and transmission were installed approx 4000 miles ago, The rattle is worse when under load, When I say worse I mean like I do everything to avoid being in that RPM range for fear of transmission damage/sanity, Running empty the rattle is there but acceptable, 4th gear being the worst more than likely because of the straight through main shaft,( Less gears/bearing interface to reduce the rattle ) Am I wrong on this theory?

Rusty I have driven other trucks with the cummins, They don't even rate when it comes to this racket, I may have to start to detune this unit to reduce the load being applied to the crank when I'm under full load, (What a shame ) I would still be willing to try the fluidampr to relief some of the torsional harmonics, but I've only found a listing for the 92's-98's & up nothing for a 1990 Cummins, but I would have thought them to be the same,

There I go thinking again

 

[THeske]

I'm thinking a imbalance on the disk/pressure plate/flywheel would result in a vibration that would increase with engine RPM's, this would produce a shake and possibly a moaning type sound as the RPM's increased

 

[RustyJC]

When the shop installed my South Bend clutch, they misground the flywheel so that it had about a 0. 040" runout. This, as would an imbalance, produced a 1 per revolution vibration that was very obvious at idle. It didn't make any noise, but it could be felt very readily through the driver's floor and, to some extent, even the steering wheel. They pulled it apart, reground the flywheel correctly and it disappeared.



As I said, my NV5600 growls pretty good down around 1800 RPM and below pulling the 5th wheel, but I know what's causing it and try to stay away from there under heavy load. I guess what I'm saying is that some racket is normal... if yours is substantially more than that, then that's another matter.



Good luck in your investigation.



Rusty

 

[THeske]

Rusty I do feel were on the same page here, But with out having a clutch disk with out some kind off dampening ability i'm sure i'm getting more than what should be the norm, before this disk was installed if you would have mentioned torsional harmonic rattle I would have said HUH whats that!!! basically there was none to be noticed, Yes putting in a different disk with torque dampening spring may be the only answer But Crappo thats a big job, If I could get away with just the fluidampr to make it more drive able when under a heavy load thats the way I think I would go

 

[RustyJC]

Rusty I do feel were on the same page here, But with out having a clutch disk with out some kind off dampening ability i'm sure i'm getting more than what should be the norm, before this disk was installed if you would have mentioned torsional harmonic rattle I would have said HUH whats that!!! basically there was none to be noticed... .

Unfortunately, IMHO, you just answered your own question. If the rattle wasn't there with a sprung disc and showed up when the solid disc was installed..... :{



Rusty

 

[Applegator]

We bought a Ford with a ZF 5 speed. From new it was chattering in third gear quite a bit. Went in to have it checked and the ford transmission mechanic said they all make that noise but yours is worse. He said the shim in front of the main bearing was to small causing the shafts to vibrate. So we bought the shim pack and fixed it ourself. Then it rattled in 4th gear a little bit, but OK. We also went to heavier oil and that helps with the rattle.



That's my experience with ZF.

 

[driverswanted]

I'm thinking a imbalance on the disk/pressure plate/flywheel would result in a vibration that would increase with engine RPM's, this would produce a shake and possibly a moaning type sound as the RPM's increased

Could this be a vibration that occurs in a range of RPM; let's say 1700-1975RPM?

 

[THeske]

ZF industries (transmission manufacture) Recommends synthetic ATF, I've also thought of a heavier oil ATF is very thin, But what are the chances of harming the transmission with a heavier oil??? Say a synthetic 0-30 weight motor oil, I would have to agree a heavier oil would help with the shear/shock pressures, But what could the consequences be????

 

[FordCummins]

My ZF6 rattles under heavy load in 3rd 4th and 5th at too low of an RPM. Specifically around 1600-1850 or so. In fact, both ZF6s Ive had behind the Cummins rattled the exact same way. It has always bothered me, but after reading this thread it looks like something Ill have to live with. Its not so annoying that I cant deal with it, but it doesnt sound good, so I usually drop a gear, accelerate up to 2250 or 2300 rpm, then make the shift to the next gear.

 

[THeske]

Anyone have some input as to where I can find a fluidampr that will fit this application, I've found sites that advertise for the later Cummins engines but none for the earlier 1990 Cummins, I'm trying to save the time/hassle of changing the clutch disk out and go with the harmonic damper change instead

 

[FordCummins]

Did you try calling the Fluidampr company? They have decent tech support.

 

[THeske]

I emailed them on the 02/02/07 I recieved their reply today, They aren't sure but the 92-98 fluidampr may fit, they sent me the dimensions, but heck that means pulling the damper measuring it & double measuring, putting it back on so I can use the truck, order the damper if it fits, pulling the damper again, I know wah wah but jeeshh there must be an easier way