Vibration at highway speed after nv4500 swap

[Ilgy85]

I've been looking around for a while, gathering knowledge and decided to swap an nv4500 into my 1984 m1008. I used a hydraulic pedal assembly from a 1986 and a nv4500 from a 1994 6.5 turbo truck with a solid mass flywheel and sprung hub clutch kit for the same truck. Everything went pretty smooth and I love the overdrive. I have 4" tuff country springs in the front and an ORD shackle flip in the rear. I ended up with 8 degree shims in the back to fix the pinion angle. My main and most aggravating problem is I have a vibration at highway speeds, 60mph+. The vibration sounds more like gear chatter than anything. It only happens in 5th gear when there is almost no load on the system. Accelerating or let off completely and the vibration goes away. The vibration is non-existent in 4th. I had a shop balance and straighten the driveshaft and install new spicer u-joints. I had the transmission rebuilt. I had the rear end rebuilt. I installed a new balancer and motor and trans mounts. I still have the same problem and it has not changed despite all the work. Does anyone have any ideas that I haven't done yet?

 

[86m1028]

I would guess trans, if issue is only in 5th gear.

 

[Recovry4x4]

Describe fixing pinion angle. What transfer case did you use? Have you confirmed phasing of the driveshaft?

 

[richingalveston]

I would suspect drive shaft but normally the vibration is under load and not under load with drive shaft problems.

Did you have the vibrations prior to tranny swap. Maybe all the work you have done is fine. I chased high speed vibrations on my truck and it ended up being the hubs. 4 new hubs, disc upgrade on the back and it is now a smooth ride.

 

[Rustyshackelford]

My m1009 with 4'' lift and stock driveline also makes a noise when I'm at top gear with no load. Just like you described it except it isn't a vibration, its just a noise. Sorry I can't offer anything besides that.

 

[richingalveston]

after reading this again, if you shimmed it up to align the shaft and still have u-joints on both ends then you may have a drive shaft alignment problem. You will probably need a cv style joint on the output of the tranny to eliminate the slight oval pattern you driveshaft is running.
If the pattern is slight you will only feel it at high speeds. The top and bottom u-joints must be as close to opposite angles as possible.
With a cv joint on the tranny end, you want the drive shaft and pinion on the diff to be in line with each other. All of the angle is done in the CV. I need a high clearance cv driveshaft from tom woods if I do not add some limit straps on my rig. At full droop my CV is hitting the stops.

does the truck feel like the vibrations are tiny surges in power?

If you have cv joint and no drive shaft problems, I would look at tranny and hubs.

 

[Ilgy85]

When the axle was shimmed, we had to put in an 8 degree shim to rotate the axle back down after the shackle flip. The axle to driveshaft angle is 1 degree lower than the transfer case to driveshaft angle. The driveshaft shop confirmed this for me when they straightened and balanced the shaft. I still have the stock np208 transfer case. I can't say if the vibration was there before the swap because I never drove it that fast with the th400 in it. The vibration does not surge. It's not really a vibration you can feel, it's really just a sound of gear chatter. It's really loud when there's is no load on the drivetrain at highway speeds. I'll look at hubs next and go from there.

 

[richingalveston]

It may be your chain slapping in the t-case. Check to see that your hubs are unlocking properly and that your front driveshaft is not turning. or possibly that you are in 4x4 in the t-case and do not know it with the hubs unlocked. The t-case chain can swell when not under load and rub the sides of the case. eventually you find it because it makes a hole and you loose all the fluid.

When in 2 wheel drive and both hubs unlocked the chain should not be spinning. I don't like the new trucks where everything is always spinning when you do not need it.

since it sounds like your drive shaft was done right, and it is probably more of a noise than a vibration, you could simply have bad bearing or sincro in the tranny 5th gear.

 

[Ilgy85]

I would get the sound even without the front driveshaft in. I don't get the noise in 4th. The noise was there before and after I had the trans rebuilt . I would have thought if it was a bad bearing or synchro in 5th then I wouldn't have the noise in 5th since neither the bearing or synchro is turning. Please tell me if my logic is wrong. This problem is aggravating and I'm quickly exhausting my options.

 

[sschaefer3]

I put an NP203/205 doubler on mine and went to a 1350 CV and a 1410 at the axle. I would be willing to bet you take those shims out tilt the diff back up again so the axle u-joint is straight and the turn is at the CV and it will be good. So I have a slip shaft and not a slip yoke.

 

[Chaski]

I'm leaning with the others on the drive shaft idea, put a CV at the case and point the pinion at it. Kind of a spendy thing to try though.

My daily driver has a New Venture 5600, I know it is different than a 4500, but it is a noisy beast of a transmission and has been since new.

Last I will leave you with a wild guess. Maybe the tail shaft bushing is worn in your transfer case?

 

[Ilgy85]

Nope tailhousing bushing in the transfer case want it either. I'll have to measure my angles again but my driveline angles are not bad. I can't see making the investment in a cv shaft when the driveshaft shop said there was no problem with my setup after they fixed my stock shaft. I'm sure they would be eager to sell me a cv shaft if I might need it. I was hoping I might find someone who experienced the same problem that could give me some insight. I'll keep looking and let y'all know what I find.

 

[Chaski]

With a single cardan driveshaft the driveshaft itself isn't spinning at a constant speed when it is at any angle besides straight. The more severe the driveshaft angle the more the shaft oscillates. There are max driveshaft RPM charts that suggest that you don't exceed a certain RPM at a certain angle. How many degrees is if from your pinion centerline to your driveshaft centerline? You might be lifted up enough that the high working angle combined with a manual transmission is making noise. If you go with a double cardan (CV) at the transfer case you divide the working angle of the joints in half and the driveshaft will now spin at a constant velocity. Another positive is that you gain some clearance under the truck when you point the pinion at the transfer case. I'm still not sure if it will fix your problem but I am curious what your working angle is.

 

[Kaiser67M715]

Did your nv4500 come with a dampener? Should be right between tranny and transfer on tail shaft. My bet is because it came from a 94, it originally had a dual mass flywheel, and then when it got converted to a solid flywheel they didn't install a dampener. The dampener gets rid of the gear chatter with light loads.


Sent from my iPhone using Tapatalk

 

[Ilgy85]

No it does not have the dampener. I am not at home for a couple days but when I get home I'll measure those angles again.

 

[Ilgy85]

I had my dad measure the angles, 10 degrees at the transfer case and 9 art the axle

 

[Chaski]

I had my dad measure the angles, 10 degrees at the transfer case and 9 art the axle

Check out this chart.

 

[Ilgy85]

Well doesn't that suck. Theoretically, at 75mph, my shaft is turning 3300rpm. According to the table, with my angles, I shouldn't go 50mph. I know the angles need to be the same and I know there is a safe operating rpm based on shaft material and diameter but this is new to be. Thank you for the knowledge. I reckon a cv shaft is in my future!

 

[Ilgy85]

Just an update. I bought the slip yoke eliminator kit and CV driveshaft from Tom Woods. The driveshaft is 3.5 inch steel with a 1350 CV at the transfer case and a 1350 u-joint at the axle end. The slip yoke eliminator is basically a shortened tail cone and output shaft with a CV drive flange. I installed it without removing the transfer case but if I did it again I would remove the transfer case first. It was a pain to put it back together setting horizontal. The CV driveshaft did the trick. No more vibration or chatter. Smooth to 86mph. Thank y'all for the advice.

 

[sschaefer3]

Awesome !!!