Drive-line noises

[amccomb]

sm 420 has straight cut 3rd and 4th gear this will cause gear whine. If you look at a modern tranny they have gears that are cut at a steep angle.

[66Submarine]

SM420 has helical gears, they are just not quite as helical as other lighter duty trans. Same thing with the M22 Muncie. 4th "gear" is not a gear at all; it's just the input shaft locked with the output--1:1. No gear noise from that, and the same goes for high gear in every 1:1 manual trans I know of.

[66Submarine]

Before someone calls me out, I will note that first gear in the SM420 is in fact a straight cut sliding gear, and not helical constant mesh. All the others are, though.

[old cool]

Dear 66 Sub,
I wish I knew how to video and such. It would be a lot easier. Before I attempt to describe again, let me tell you what model and components I have. Truck is a model 1000, swb. Trans is a synchronized 3 speed stick that shifts very well. I believe its a Saginaw trans as I saw one with same numbers on ebay. I was told the differential is a model 44 Dana (it has 10 bolts around cover and I see no tags for posi.
To answer your last question, yes, I hear the whine more when I push the clutch in between 1st and 2nd. The sound is higher level pitch and steady. When I accelerate in 1st and 2nd the sound is less noticeable as it is overpowered by the sound of the engine rev. In high (3rd) the sound is steady unless I step on it then it's overpowered again by sound of engine.
I forgot to mention in earlier posts that the sound is much less and more tolerable between 35 and 40 mph. That's probably a huge variable. Just thought about it.
In your 2nd video, (someone driving), I noticed that my truck sounds almost exactly the same through 1st and 2nd. However, I did not notice a noise in yours while cruising in 3rd. I definately have a whine.
Lastly, I do now notice a vibration in steering wheel around 30mph as I'm rolling to stop. That is what has also drawn me to threads on drive shaft and u joints.
Let me know if I'm posting too much info at once. I tend to read several threads and that gets the wheels turning (no pun intended).

[66Submarine]

Does the whine happen with the clutch in and the truck stopped and not moving? When the truck is stopped, only the throwout bearing (and pilot bushing, if you want to be technical) is spinning when you have the clutch pushed in, so that will tell you if the throwout bearing is also loud. (BTW, you should have about 1" of clutch pedal travel before you feel it touch the throwout bearing and become more firm.)

In my video of my truck, when I'm not in high gear you are hearing the transmission gear whine--pretty normal for that trans (light duty trans are quieter). BTW, here are some pictures of the Muncie SM318 that most of these trucks came with: http://67-72chevytrucks.com/vboard/s...d.php?t=574428 The later Saginaw will be much larger and have seven side cover bolts.

If you were actually in the truck with me, you could also hear a slight whine from the worn ring and pinion when cruising in high gear. Not a lot, but enough to hear over the (fairly loud) exhaust at times (I do have decent hearing). So, I'd say at least part of your problem is ring and pinion damage/wear. One possibility is that the guy working on it before might not have really known how to set one up, and left the pinion slightly loose when he changed the seal. If he did, the pinion bearing/pinion will also be slightly loose as a result, which would make it whine.

So, I think at least some of what you are hearing is the ring and pinion. It may or may not really be a problem, depending on how loud it is, and why it's loud to begin with.

If you have one of the new phones with the built-in cameras (or know someone who does--they pretty much all do now), just set it on the dash or something and have it recording for a minute or so while you are driving (preferably while you also work the throttle to see how the sound changes)--all that's important is the sound.

Youtube/Photobucket/etc. is pretty easy to figure out, but you could also text me the clip to my phone if you don't want to do that. Just let me know and I'll send you my number via the private messages.

Hope this helps,
Chaz

[old cool]

Been tied up so haven't been getting back lately. Sorry, I know you guys have a busy life, yet, you took time out to respond. Much appreciated. I'm not too great at using technology, but maybe I can get someone to help me post the drive train sound in a video.
For the purpose of throwing out a new idea, has anyone ever experienced noise coming from older style radials. I have Firestone FR380 narrow whitewall probably from the 90's. They only have about 1000 miles on them.

[old cool]

Hello
I sent in a question regarding the possibility of radials from the 90's adding to drive line noise. (the tires are still like new) It didn't get posted. Am I doing something wrong? My post was moved up but my latest question did not get included. Oh well, here it is again:
Just wondering if anyone has had experience with narrow type radials (from 90's) causing a whining noise through the cab? Thanks

[66Submarine]

Your message shows up fine for me.

Tire noise is generally pretty much totally dependent on speed, and normal "highway tread" passenger car tires shouldn't really be too loud (IMO/IME).

I'd get some new tires, though! I have a lot of blown up radials laying around my compound, and most were only eight or so years old when they let go. Vibration in the wheel could certainly be tires with bulges in them, too.

[old cool]

Hello my friend,
My brand and tires (380's) were recalled in late 90's but in the 235/75 size. I have 225/75. No mention of recall for my size but it makes me wonder. I believe there was a belt, bulging, and tread problem. That's why I brought up tires in my most recent post. I'd hate to go through a dozen mechanical possibilities only to discover it's tires.
FYI, the tires are perfect looking from the outside - sidewalls and between treads.
Thnks Chaz,
Ted

[Sharps40]

Sumthin jes hit me...ya got tires on yer truck from the 90s? They's prolly gonna be noisy, recall or not just from shear rotting and separation/movement of the belts in weak rubber.

[padresag]

there are a few things to think about first. 1 you can't get grease in the ujoints- remedy that and that will eliminate that. there is no such thing as a tight pinion seal either they fit or they don't and if they don't fit then they are not the right one. no one on here can really tell you what the noise is; they can only guess. the easiest solution is either get it up on a hoist or stands where you can run it in gear and listen to the trans and or rear axle with a stethoscope and pinpoint where the noises are coming from as there is more than likely more than one source
ron

[old cool]

Thank you for suggestions re testing Padresag.
Sharps40- the tires are about 5 years old. I meant 09 not 90. Sorry.

[old cool]

I think I got started with this thread. lol. Anyway, I moved on to timing problems, alternator alignment issues, popping noises, drilling muffler hole, etc. Still dealing with some issues; others fixed. So, I'm back on the drive-line issue because I found a thread that was more definitive than mine. (Humming while coasting; hence, clutch in and in 3rd gear with little load. Hope this helps others seeking a description. See thread 386889.
My sincere thanks to all that tried to help me.
I've been posting a little less as I have been taking advantage of the Q&A section.
God Bless. Hope everyone had an enjoyable 4th.