Hello Group, Truck is running really well. It is a daily driver that runs like a top. Current issue is this: there is a vibration that occurs while driving that only happens at about 45 MPH then stops when you hit about 50. Very narrow MPH range where it occurs. Otherwise there are no vibrations to speak of. Tranny was rebuilt about 50 miles ago and clutch is new. Let me know your thoughts. WHat types of issues would exhibit vibration at only certain speeds?? ALso seems to do it in 2nd gear if I rev it up to get speed to 45 MPH. Motor is 235 and runs pretty strong.
Could Be A Couple Of Things, Ujoints, Carrier Bearing, Drivelines Out Of Balance, Flat Spot In A Tire. Put The Truck Up In The Air And Have A Friend Run Up The Mphs And Use A Stethascope Or Srew Driver And Listen To The Differental, The Carrier Bearing And The Tail House Of The Tranny To See If You Can Narrow It Down To One Part Of The Drive Line. Thats A Good Place To Start.
Try getting it to the vibration point then let off throttle and dump the clutch IN. May help isolate a driveline vibration, to a wheel/wheel bearing problem. DVal
THanks Kustom, I am not familiar with the carrier bearing. I thought this was only with two piece driveshafts. Please advise. My truck is as light duty as it gets: C10 1/2 ton with 235 and light-duty 3 speed on column. ALso dont think its tires. Just had all tires replaced and it still does it. Thinking maybe u-joints. Hoping not the rear end itself.
"Thinking maybe u-joints. Hoping not the rear end itself." The rear would be making noise if it were going south. Check the mounting bolts, that should be the only thing to look at for a vibration problem.
DValentine, thanks. Now if the vibration clears up when I clutch in at 45 MPH, how would you diagnose further to determine cause? How do you determine if wheel bearings are bad, etc. THanks so much!!!
If it clears when you clutch, wouldn't that mean a drive line? I think your drive shaft may simply be out of balance, or hooked up improperly. Did you rebuild your tranny or did someone else? If someone else did, check and make sure he put the driveshaft on correctly. I had a guy rebuild mine. 500 miles later, it burned up because he had his "temp" help install the tranny, and this uneducated fool put the drive shaft on without noticing it was WAY too long. Bottom line is, mistakes get made, even by "professionals." I agree with DV about the rear end, it would make noise. Mine rear end went out and howled like a dog at the moon. It would howl louder at 45 than any other speed, but it never actually vibrated the truck. I believe u-joints make noise too before they go out, but I'm not totally sure. Good luck!
BTW, wheel bearing start throwing grease if they go bad, I believe. Are your front wheels dirty, do you have grease in your center caps, etc?
Aimless and group, Here's an update regarding the vibration. Last night I took her out for a nice ride. Vibration is there at 45 MPH. WHen the vibration starts, I pressed teh clutch in slightly and I felt the vibration through the pedal. Above 45, no vibration smooth as silk. Below 45, no vibration smooth as silk. At 45, definite vibration that is clearly felt in clutch pedal. NOthing crazy, but definitely there. Tranny was rebuilt about 100 miles ago by a reputable guy. Clutch was also replaced at the same time with all new parts. Of course, people can make mistakes. COuld this still be a driveshaft issue (out of balance or U-joint?). What are some things to look for. I'm gonna have an old gearhead friend of mine drive it and see what he thinks. ANy advice is welcome and thanks in advance.
I'd say your driveshaft may just be out of balance then. I believe u-joints make noise before they go. Call the guy that rebuild your tranny and ask if that's "typical." See what he says. Maybe he know something, or something happened and he forgot to mention it . . .
With the truck OFF, and In Gear, crawl under and grab the driveshaft. Try moving it both around, like it normally moves, and front to back. If it moves excessively, ( trust me, you will know how much is too much), then it's probably the U-joints. DVal
DVal, Aimless, everyone else, Youve all been great and given great advice. That's what this board should be all about. I contacted a driveshaft specialist in my area and he strongly recommended having each tire checked for balance before doing anything. He said that in most cases, its a wheel issue rather than driveshaft when it comes to these types of vibrations. I will check driveshaft for looseness tonight. I hope this is not tranny/clutch related. ALthough, the guy who rebuilt the tranny guaranteed it for as long as I own the truck. He is an old school builder who actually used to build 283's back in the 60's and GUARANTEE them never to blow. And they never did. He spends hours deburring and polishing rings and other parts before he even begins assembly. So he knows what he's doing, but I guess you never know. I will let him know the issue and see what he says. He's away on vacationow so I have to wait a week or so. Incidentally, here's something else. THe tranny is the standard 3-speed light duty model. Dude who rebuilt it says it's a Muncie. Anywhoo, I find that 1st and 2nd gears are fairly "low feeling", but when I shift to third, it feels very "high". In other words, it feels like, with a four speed, if you go directly from 2nd to 4th. 3rd feels very high this way, but then recovers after she gets up to 45 or so, and you can tell the motor is revving pretty good once you get to 50-55. This is kinda weird to me. Perhaps since it is only a 3 speed, you need to have third be a bit higher since there is no fourth gear to go to. Anyone else have this three speed and if so, is this normal????
Haha, yes, do make sure its off first. Have the guy check it, but in my short time on this earth, it seems to always be the old feller in his shop that can outbuild anything the college man puts out. As far as you gearing goes, I have never personally owned a 3-speed manual tranny and I've only driven one one time. My old set up in my truck had a 250ci I6 with an SM420 - a four speed manual but 1st was a "granny gear" so you'd never use it - you start in second. Second and third were pretty low, fourth was higher (and acted just as you describe your third gear) but the truck topped out and ran very hard at about 60-65 because my rear-end gears were 4.10. My grandpa's '63 has a 283ci V8 with an SM420, and his truck would run 100mph fairly easy . . . his rear-end ratio is 2.73. Bottom line is you can get a three speed running closer to highway speed, but you need the right rear-end ratio that corrisponds to the tranny. You are right, because you have three gears, you will always run a little harder than if you had four or five. But you can make it a little better.
Aimless, Thanks again for the comments. I believe the truck came stock with 3.90's in the rear, which is pretty low and yes, at about 55-60, the motor is revving pretty good, well over 3K RPM's I'm sure by the sound of it. My feeling is that these trucks werent meant to go much faster than that anyway. I had a 66 Fleetside with a I6 and the SM420. God I loved that tranny. Great for moderate hauling. Wish I had one in the 62. THanks for the help. I'll be working on her over the weekend to find the source of vibration. Mark
ANd yes, youre right about the old feller in the shop. This guy was a fairly well-known racing dude in the 60's. Ran 66 Chevelles with 283's. He's a major believer in the 283. He could build a 283 to pull the front tires off teh ground (I've seen the footage) and his 283's routinely blew away big blocks. Like I said, he used to build em in the 60's and guarantee them for life. He taught me alot about motor assembly and some of his tricks are interesting. He always told me if you build it right, it should never blow, even if it's beat on. ANyway, he built my tranny and is also a Muncie M-21/22 specialist. He's about 70 now and sharp as a tack. I would trust him over any college boy builder any day of the week.
Too bad you didn't live closer. I'd have you run over to my place, put some money in my coffee can, and leave with my old SM420. I still have it and the 250ci, and I talk myself into keeping them sometimes because I just "know" one day I'll rebuild a '50 pickup . . . which will probably never happen.
