NV3550 Noise

[Jambi]

Did an NV3550 conversion over the winter and things have not gone smoothly ever since. Early on, I posted about not being able to shift into gear, but I was able to get that resolved. Now the issue I'm trying to figure out is a noise being made when driving. It's hard to describe the noise, but the best thing I can come up with is it's like dice rolling around in a Yahtzee cup or like a dryer tumbling. The noise occurs when in gear and in every gear.

I had the transmission rebuilt by a transmission shop that my drag racer neighbor recommended to me and the shop owner who did the rebuild recommended I use Mobil 1 5W 30, full synthetic oil in the transmission. I filled it until it came out the fill hole. Could I need more oil? A different oil? Is the noise unrelated to oil?

I've been so frustrated with this NV3550 install, I'm contemplating putting the C4 back in!

 

[Timmy390]

5-w30 is COMPLETELY wrong for ths nv3550. You want Mopar fluid (part number 04874464AA). Some have used Pennzoil Synchromesh with good results. I run Synchromesh in my M5ODR2

Tim

 

[AZ73]

5-w30 is COMPLETELY wrong for ths nv3550. You want Mopar fluid (part number 04874464AA). Some have used Pennzoil Synchromesh with good results. I run Synchromesh in my M5ODR2

Tim

Exactly. The NV3550 has brass synchronizers and the Mopar (or Pennzoil like I also use) has the right viscosity and friction characteristics for the synchronizers. Probably why you're having a problem shifting. Other oils are either too slippery, don't have the correct friction level, and have too much ZDDP (sulfur-phosphorus EP compounds) which can corrode the brass synchros.

 

[Jambi]

Well that's unfortunate! I will get one of the two oils mentioned and see what happens. Thanks for the replies!

 

[73azbronco]

Yeah, always use factory recommended fluid.

The nv4500, uses a specific mopar fluid, and it is the only fluid that works in the 4500. I know they are different.

 

[DirtDonk]

And while you’re doing all this, check the angles on the driveshaft and rear pinion.
Did you also have a suspension lift installed by any chance? Or are you still running stock height?

Either way, the length overall of the rear driveshaft has changed, so I’m just mentioning this in case there’s an angularity problem that’s creating a vibration.
You don’t always feel it, but with the 3550 having kind of “loose tolerances” for lack of a better term, driveline vibration will usually result in a rattle in the transmission.
Do what the others said about the lubricant, but check pinion angle too.
You could easily have a double dose of issues.

 

[Jambi]

I changed the lubricant to the Pennzoil Synchromesh and still have the noise.

I do have a 3.5" suspension lift. Measured the rear pinion angle and it's at 23 degrees. Rear driveshaft angle is measuring 27.2 degrees.

With the N3550 conversion kit, does the transfer case end up sitting higher than it does with the stock crossmember and C4 transmission? Just wondering if installing the NV3550 increased the angle from rear pinion to transfer case.

I don't even know if it's the transmission that's making the noise, I just assumed it was since that's the big thing that's changed and I didn't have the noise when the C4 was in.

I should mention after the initial install, when I took it out for test drive I had the noise, which led to a bigger issue that caused me to drop the transmission and go through things. Came to find out the rear output shaft bearing of my transfer case was chewed up and I have no idea what would have caused that. But since I had everything out again, I ended up getting the Extreme Duty Dana 20 Output System ( https://www.wildhorses4x4.com/early-bronco-extreme-dana-20-output-system-assembled-with-speedo-parts) so that's also new. I'm really hoping whatever caused the old output shaft bearing to get chewed up doesn't cause the one in this new output to get chewed up.

 

[Dude 713]

Does the noise stop when you push in the clutch? If it does my guess would be the throw out bearing.

 

[Jambi]

The noise does not stop when the clutch pedal is pushed in. As I was driving again yesterday demonstrating the noise to a neighbor of mine, I demonstrated how the noise does not occur while sitting in the driveway idling, or when I first push the clutch in to put it in gear to begin moving. But once I start driving down the street, the noise becomes evident regardless of what gear I'm in. Then as I come to a four way stop, push the clutch in, throw it in neutral, the noise persists as I coast to a stop. While at a full stop, no noise. Also while driving, I put it in neutral after being in third gear, and as I was coasting in neutral, revved the engine and the noise still persisted. Not sure if this information helps, but I'm trying to provide as much detail as I can with things I've tried to get this figured out. So, the noise does seem to only occur while I'm moving whether the transmission is in gear or neutral and coasting.

 

[Timmy390]

Jack stands....get the rear up on jack stands. Have someone listen for where the sound is coming from.

Tim

 

[DirtDonk]

Take a picture of your rear u-joint area and pinion.
Take it from as close to the side as possible so that we can better gauge the angle.
That 4° discrepancy is enough to cause trouble, even though it’s not really a massive offset. Should be more like 1°. But it looks like the pinion angle is higher than the driveshaft angle? Or is that lower?
The 3 1/2 inch lift is enough to put off the angle itself, and the shorter rear driveshaft is enough to make it worse. I’m not sure exactly what the heavy duty Output Shaft does to that length.
Are you’re using angled shims between the springs and spring perches?

While you’re under there, taking pictures, if you can take an overall picture of your drive, shaft, front view, joints, and rear, that would be great too.

Thanks.

 

[AZ73]

Did you put angle shims in the rear springs when you lifted it?

Steel 6-Degree Leaf Spring Shims, 66-77 Ford Bronco

Check out the deal on Steel 6-Degree Leaf Spring Shims, 66-77 Ford Bronco at WILD HORSES 4X4

www.wildhorses4x4.com

 

[Jambi]

Did you put angle shims in the rear springs when you lifted it?

http://[URL]https://www.wildhorses4x4.com/early-bronco-6-degree-leaf-spring-shims

[/URL]

I didn't, but I think I'm going to order those today.

 

[AZ73]

I didn't, but I think I'm going to order those today.

I personally think they're necessary anyway but you don't want to be chasing the problem by throwing parts at it. You should still get it up on a lift or jack stands, or even try a go-pro camera under your truck recording while driving to diagnose it. It could be something as simple as you didn't tighten the trans to the cross member or the cross member to the frame.

 

[gnpenning]

Some good suggestions. Off the track here, have you checked the axle bearings or even pinion bearings ??

Don't forget front bearings and making sure you are in 2wd.

 

[Jdgephar]

I would check front and rear drive shaft for all joints. After that, jack up and spin both rear wheels in neutral. Perhaps you have pieces of brake shoe or rocks in the drums. Could also be bad wheel or axle bearings. Also check for any play at the output of the transfer case.

 

[Jambi]

All good suggestions, thank you! I have not checked axle or pinion bearings yet. I was wondering about the safety of getting it up on jack stands and having someone run through the gears while I tried to pinpoint exactly where the sound is coming from underneath, but that just seems way too risky and like an accident waiting to happen. It's just when inside and driving it's really hard to determine where exactly the noise is coming from.

In an attempt to see the effect of a decreased pinion angle and possibly simulate what the shims would do, I lowered the transmission crossmember so the two upper bolts of the crossmember were mounted to the two lower bolt holes in the frame thereby dropping everything down 1-2 inches. This decreased my rear pinion angle. I then took it for the same drive up my street to see if the noise still occurred and it was gone. I didn't get above third gear, but the noise was gone where it was present before. So, I did order the 6 degree shims and will install them this weekend. Fingers crossed that'll be the fix!

 

[73azbronco]

Or, washers that lower the rear of transfer case?

 

[Jambi]

I installed the 6 degree axle shims and I'm still hearing the noise. I tried attaching a 30 second audio file of the noise, but it's not attaching. Unfortunately, I think I have no choice but to drop the transmission.

 

[jamesroney]

I installed the 6 degree axle shims and I'm still hearing the noise. I tried attaching a 30 second audio file of the noise, but it's not attaching. Unfortunately, I think I have no choice but to drop the transmission.

PLEASE perform some diagnostics before you drop the transmission. You have an opportunity to learn some valuable information before you get started.

Step 1. UNLOCK front hubs.
Step 2. Drive the Bronco in 2WD and make the noise. Determine whether the noise changes frequency with engine RPM, or with Bronco speed. (It's one or the other...)
Step 3. Shift the transfer case to 4WD. See if that changes anything.
Step 4. Shift the transfer case to 4Lo. See if that changes anything.
Step 5. Remove the rear driveshaft. Shift back to 4Hi. Lock front hubs. Drive in Front wheel drive (hi) and see if the noise changes.
Step 6. With hubs locked, Shift to 4 lo. Drive in Front wheel drive (lo) and see if the noise changes.
Step 7. Set the parking brake. Remove the front driveshaft. Shift to 2Hi. See if the noise persists if there are no driveshafts in it.