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Hello everyone reading this,


I'm new on this forum so first I would like to introduce myself and my Dodge.
My name is Jaron and I'm from the Netherlands (so sorry if my English isn't perfect). I work at a classic car dealer as a mechanic and salesman (so I'm not unfamiliar with car technics). I'm 23 years old and beside the Dodge I own a 1950 Nash for a nice sunny day in the weekend and a BMW race car.

I have a 1969 Dodge D100 318 with the np435 gearbox. I use it as a daily driver and drive about 70 miles a day.
It has the original 318 v8, but equipped with headers, edelbrock intake and camshaft and an msd electronic ignition. It runs on gasoline and lpg (not at the same time of course).

It is a very nice driving and reliable car, but there is one thing I'm not fully confident about and that is the gearbox.
It shifts very nice, upshift and downshifting goes nice an smooth with no weird sounds what so ever.

But when accelerating or at constant speed the gearbox makes quite a loud low sounding noise. A bit like a worn wheel bearing, but louder. It is defenitly the gearbox making that sound. It is quite an irritating noise, especially because the rest of the car is actually nice and quiet (for an old pick up).

I was wondering if that was a normal sound to make for the gearbox (and if not what it could be), or that it needs a rebuild. I've driven a few old Ford pick ups that should have the same gearbox as far as I know but they don't seem to make that noise. It is quite a rare car in the Netherlands so I can't just ask someone if I can try their Dodge d100.


Already thank you for the comments.

Welcome!
Is the lubricant (oil) level correct? Does it look dirty?

Bucky

712edf wrote:Welcome!
Is the lubricant (oil) level correct? Does it look dirty?

Bucky

And does it have the correct lubricant. No ATF. No 30 wght. 80/90 gear oil minimum only.

Oil level is correct. It doesn't leak or anything. I use 80w90 mineral gear oil in the Dodge. Replaced the oil a few months ago because of the noise, but didn't make a difference.

It is a dirty and old looking transmission. Doesn't seem to have been rebuild before.

When I replaced the oil I've checked the old oil for dirt or metal flakes or anything, but it was actually quite nice an clean and smelled like normal gear oil.

Check the u-joints.

I've checked the u-joint's, but they seem to be fine. No play or anything.

I wanted to make it drive with the rear wheels of the ground while standing on a bridge (do you call it that way in english?) in the workshop. But I was alone there today so wasn't able to do it. I will try again when I've got some help, mayble I'm able to locate the sound more precise then.

Thanks for the comments so far.

I would suspect either the throw-out bearing or that large bearing that supports the transmission input shaft.

Does it get quieter in 4th gear? If so, in or output bearing. If you put it in neutral is it noisy? When driving, if you push the clutch, does it get quieter?

It keeps making noise when you put it in 4th, but it seems to be louder in 2th an 3th. When you put it in neutral the noise is gone in a few seconds. Operating the clutch makes no difference.

I've noticed one thing yesterday. I was a bit in a hurry so I drove it quite a bit faster (80+ mph) than I normally do and it actually seemed to make less noise than it does at a little bit lower speed. But it could be misleading because there was quite a lot more engine and wind noise. And I'm not going to do it again because it drives terrible at that speed It was still rock solid on the road, but the noise from everywhere

I'm still not really certain where the noise is coming from and still haven't been able to lift the car up and listen to the gearbox when the car is driving in the air.

I'm curious to see if a bad pinion bearing isn't transmitting the sound through the drive shaft. When you get the tires off the ground if the noise goes away that's where I'd look.

I'm hoping to be able to find out tomorrow, but I need some help doing it so hopefully I would get some help tomorrow.

I deal with the same issue. It's just me and if it requires more than one I have to wait until someone can fit me into their schedule.

Check your midship bearing. The support bearing for the two piece drive shaft.

If it gets quieter in 4th, it is either the input bearing or a countergear bearing. It is best to get it on a lift and pinpoint it with a stethoscope.

I'm planning on doing that, but still haven't been able to. One of the mechanics is sick and the other one is on a vacation, so I'm alone in the workshop at the moment and need some help doing it. I will put it on a lift as soon as I have the possibility.