NV4500 downshift Problem...

[dirtywhiteboy40219]

Hello from Germany....

I just installed a Valair single organic disc in my truck. The previous clutch went bad due to the input shaft seal leaking, y’all know the rest. I did replace the seal. I got the whole clutch kit from Valair, 13“ flywheel, pilot, throwout, etc. Even went the extra mile and got the ARP flywheel bolts.

The trans used to rake a little on the 2-3 shift if I was beating on it. Gotta show those pesky German VW drivers what the ‘ole dually can do from time to time.

After the clutch install, I can’t do a 4-3 downshift, at least like I used to. If I slow down to where I normally would shift to second, it will go into third. I never had any downshift issues before.??‍♂️ I don’t believe it has anything to do with the clutch. The only other thing that changed is the noise when lugging it. It used to make the rattle in third, now it rattles in fourth.

The pedal feels good, has a good, smooth engagement. Up shifts for all gears is just like before. First and reverse work perfectly. Fifth gear engagement is also great.

Y’all have any ideas why I can no longer do a 4-3 downshift? 
thanks for any and all help!

[Haggar]

DWB,

 

Welcome to the forum!

 

If you went from the stock 12 1/4" to 13" you increased the rotating mass of the clutch.  (would be neat to know the weight differences to calculate the moment of inertia)

But if you think about it, the synchros provide the energy necessary to change the speed of the input shaft (up or down) to allow the gears to mesh properly.

You have changed the moment of inertia of this input shaft.  So the timing is going to be a bit different.  (you have added more load.)

You may need to work on speed matching a bit better.  You are asking older synchros to do more work now.

 

Have a great day!

Hag

[Mopar1973Man]

Most likely a syncro issue maybe or pilot bearing issue. Pilot bearing fell out of my South Bend Clutch and ruined the input shaft but it made shifting down troublesome. Syncro wise you could have the same issues too.

 

I just lost 2 sets of brass syncros (defective). The first set 3rd and 4th gear were just hard both up or down. Second set I lost 2nd gear syncro now that's a pain in traffic to struggle with launch again. I'm now running brass syncros and doing good. 

 

Still running Mobil 50 SAE GL-4 fluid Synthetic. 412k miles and rolling again.

NV4500 with dual disc Valair Clutch

Edited May 18, 2020 by Mopar1973Man

[dirtywhiteboy40219]

On 5/18/2020 at 3:17 PM, Haggar said:

DWB,

 

Welcome to the forum!

 

If you went from the stock 12 1/4" to 13" you increased the rotating mass of the clutch.  (would be neat to know the weight differences to calculate the moment of inertia)

But if you think about it, the synchros provide the energy necessary to change the speed of the input shaft (up or down) to allow the gears to mesh properly.

You have changed the moment of inertia of this input shaft.  So the timing is going to be a bit different.  (you have added more load.)

You may need to work on speed matching a bit better.  You are asking older synchros to do more work now.

 

Have a great day!

Hag

Explanations like this are why this forum is the best.????
It works “ok” if I really granny shift it. Only then. It will go into third on a downshift IF I’m going at a speed where I’d go to second.

Now I’m curious if I made a mistake opting for the 13” clutch. You nailed that one!

Its frustrating because it NEVER had a problem with downshifting before.

Sooooo, with this new found knowledge, replacing the transmission isn’t gonna fix this either? Fourth gear makes a lot of high pitched noise now too. All this because of the flywheel??

wish I’da known this going in.

On 5/19/2020 at 1:35 AM, Mopar1973Man said:

Most likely a syncro issue maybe or pilot bearing issue. Pilot bearing fell out of my South Bend Clutch and ruined the input shaft but it made shifting down troublesome. Syncro wise you could have the same issues too.

 

I just lost 2 sets of brass syncros (defective). The first set 3rd and 4th gear were just hard both up or down. Second set I lost 2nd gear syncro now that's a pain in traffic to struggle with launch again. I'm now running brass syncros and doing good. 

 

Still running Mobil 50 SAE GL-4 fluid Synthetic. 412k miles and rolling again.

NV4500 with dual disc Valair Clutch

Thanks for your response. I’m running Amsoil 75-90 MTL. I’ve been using this since I’ve owned the truck. Amsoil ships to me where I’m at. The truck has around 285k miles. It was used to Schlepp a small backhoe around the German Alps for 15 years. I don’t think it ever saw fifth gear use.

These little faux paus make me miss the old NP435’s.

How hard is it to rebuild an NV? Do you need any special tools? Are brass synchros a better choice for normal driving/ light towing?

It rakes hard on up and downshifts if I drive it “normal”. 1800 rpm upshifts sound like shrapnel. But it will go in. Could that be a throwout bearing?

Thank you all again for your help!
 

[Haggar]

DWB,

 

You may want to pop the tranny out and see what is going on.

 

Mike (moparman) had made a good point on the pilot bearing...  If that is damaged or dragging, similar issues will happen.   No I think the 13" is a good replacement.  Where we usually start seeing inertia problems is on the dual disc setups.  That has a significantly different inertia load.

 

I am spooked by you saying it is noisy in 4th gear.  Fourth should be the quietest gear.  power is direct from input shaft to tail shaft.  that is the least amount of gears and bearings in operation.

 

The NV4500 is not as complicated (apparently) as the NV5600 is.  (as far as special tools go.)    I just did a quick check and kits seem to be pretty available and there are a couple videos out.  It seems straight forward.

 

GL

HTH
Hag

[Mopar1973Man]

7 hours ago, dirtywhiteboy40219 said:

Now I’m curious if I made a mistake opting for the 13” clutch. You nailed that one!

 

No. I'm also using 13" clutch but a dual disc. Valair Dual Disc Organic.