Weird Trans Noise help!

[Doug F]

Hey guys, I got my 67 on the road and drove it home last night without issue, it needs an alignment and such, but the issue I am inquiring about is a weird noise when in 4th gear and coasting down hill. It sounds kind-of like a mix between a can of coins rolling on the floor and a screw driver rolling off a wooden table. However, when coasting (in 4th gear) on flat roads, it is pretty quiet; also when coasting in Neutral it is quiet too.

The trans is an NP435, the odo reads 98,098 miles, I don't believe it is 198k.

Any ideas? Throw-out bearing? I know the name, but not what it does...

Thanks.

[BRUTUS_T_HOG]

will the noise change if you pull the shifter into 4th harder? does the harshness transfer up to the shifter?

sounds like worn gears or shift collar.

the throw out bearing is for releasing the clutch and should not be related to drivetrain load

[Doug F]

Hey Brutus,

I will check that later... I know the shifter is quite sloppy, like it has the full 98k miles on it, I am waiting to swap in my "new" 1978 NP435/NP205 combo, until I can get a couple drive shafts.

Someone suggested input bearings could be an issue as well. I now just pop it out of gear when coasting down-grade. Might a heavier 75w 140 oil work to quiet things down?

[BRUTUS_T_HOG]

heavier oil might barely quiet things down.. but will also just bog the engine down more

and the input shaft bearing would make noise in every other gear except 4th.

[70_F100]

and the input shaft bearing would make noise in every other gear except 4th.

Incorrect info, my friend!!

The input shaft bearing should make noise in ALL gears, even neutral, as it spins whenever the clutch is engaged with the engine running.

Now, the pocket bearing inside of the input shaft (where the mainshaft pilots) would be subject to make noise in all except 4th, as that is the only time both shafts are spinning at the same speed and locked together.

[BRUTUS_T_HOG]

thats correct, but in 4th gear there is no load on the counter shaft that would normally be trying to push the input shaft away and putting load on its beaing

both of those bearings can make similar noises.

[Donnie]

The noise that he is describing does not sound like a bearing. A bearing would growl or at least sound like what he has described. To eliminate the input shaft bearing. engine idleing in neutral, press in the clutch this will bring the input to a stop & the noise if it is the input will stop.....Donnie

[Donnie]

I meant NOT sound.......................Donnie

[BRUTUS_T_HOG]

The noise that he is describing does not sound like a bearing. A bearing would growl or at least sound like what he has described. To eliminate the input shaft bearing. engine idleing in neutral, press in the clutch this will bring the input to a stop & the noise if it is the input will stop.....Donnie

we know that. OP asked about the input bearing

[Donnie]

Excuse me ASE, but the large input shaft bearing makes a TOTALLY dif. growl than does the small front output shaft bearing.. I have retipped many output shaft's on other units that were bad on teardown & there was very little sound that you can detect from this small bearing..
From all I have read on this thread, you may be right with you comment about the shift lever/ spring/ tower.......It is just that I don't quite understand the original posters description.
He didn't answer your original question about shifter shake / or holding the shifter???????/Donnie

[BRUTUS_T_HOG]

OP said he would try it and never answered... and asked if the input bearing was a possibility and i said it didn't sound related

[Doug F]

Hey guys,

I drove it to work today, no the shifter doesn't shake and the noise doesn't go away by holding the shifter in gear.
Growling is the term I couldn't think of...
The noise is in 2nd and 4th, not so much in 3rd. There is no noise in Neutral and no noise when depressing the clutch, just coasting in gear WITHOUT load. Coasting up hill or on flat, there is no noise. Also there were a few times where it wouldn't shift into 4th, it felt like I was being blocked and it would lightly growl and still not let me get into 4th... UGH! I put it back into 3rd and then drove a bit more and then it would slide in effortlessly!
The whole half hour trip I listened to all the noises from everything! There were some tap tap taps while driving along, which sounded like it came from the front.
All this sounds like, from your diagnosis, like it is an inside the case type of noise... So putting the newer (78) shift tower on, probably wouldn't do anything?

I appreciate everyone's input, I am still learning!

Doug.

[averagef250]

Sure it's the tranny? How's the rear axle? transfer case?

growling in 4th gear decel is not a normal bad trans symptom.

Usually, you get a different sound between direct gear and all others when there's a bearing issue with a stick. countershaft bearings growl in R-1-2-3, but quiet in 4th. a Bad input bearing and you'll have major noise on acceleration in 1-2-3. Bad pocket bearings aren't usually noisy. Bad output bearing totally dpends on the tranny design, but you can usually spot one by the leaks at the back of the trans and excess noise under load in the rearmost gearset in the trans.

[Doug F]

Hey Dustin,

I can never be sure, except that when I slide it into neutral, the noise goes away. My D21 T/C is brand-new and the rear seems pretty good... I know the only odd thing in the drivetrain is that the rear is 3.70 and the front is 3.50, so I don't use the 4wd in it until I get my newer front axle built. This is probably why it has a new T/C because someone blew-up the old one due to the mis-matched gearing. It is a head-scratcher for sure!

[averagef250]

Take the rear driveshaft out and drive it on the front axle, see if the noise goes away. You might find a whole new set of noises if your front axle is a bit loose, but it might help narrow down the issue.

Growling on decel is a typical bad rear end symptom. Often it won't do it in nuetral, just when the load from the engine braking is going through the gears.