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odd shaking problem
https://slantsix.org/forum/viewtopic.php?t=20452		 Page 1 of 2
Author:  pushitonme [ Mon Oct 23, 2006 6:51 pm ]
Post subject:  odd shaking problem
Sorry guys, I'm a newbie and I know I'm asking a lot of sporadic questions in a short amount of time, but seeing as you are all so nice and seem to have a plethora of information, I figured I'd start unloading some of my lingering concerns.

So...my '83 d150 has an a833 four-speed with an 8 3/8" rear end. When I bought the truck, it had obviously been taken out in the swamps and water got in everything. I have completely redone the entire rear brakes, and I replaced the input shaft bearing, axle bearings, and all appropriate seals. When I had the rear end apart I inspected the gears for pitting, scratching or wear, and suprisingly enough they were in excellent condition. So I put it all back together. Oh yeah, u-joints were replaced as well.

For some reason, when I am going between 35-45mph and I take the load off of the engine, i.e. press in the clutch or put it in neutral to slow down, my truck starts shaking fairly violently, but once I go below 35, it smooths out. Does anybody know what could be causing this? The tires are in pretty rough shape, so that's a possibility. Also, I noticed a small dent on the driveshaft while replacing the u-joints, could this be the problem? Other than this one issue, the truck rides smooth, no grinding, scraping or anything else. I'm pretty well stumped...any ideas? Thanks.
Author:  SlantSixDan [ Mon Oct 23, 2006 7:11 pm ]
Post subject: 
H'mm. Could be a driveline balance issue, a rear axle pinion angle issue, an engine/trans mount issue...
Author:  66aCUDA [ Mon Oct 23, 2006 7:13 pm ]
Post subject: 
Certainly could be the tires. I bought a truck and couldnt go more than 35 or it would rattle you to death.
Try them first and then if it doesnt fix ask the Forum again :)
frank
Author:  SlantSixDan [ Mon Oct 23, 2006 7:23 pm ]
Post subject: 
Quote:
Certainly could be the tires.
Usually a tire-centred vibration is simply speed-sensitive, and won't respond to engagement/disengagement of drive. In this case, the original poster has stated that this vibration is sensitive to whether he's driving or coasting.
Author:  pushitonme [ Mon Oct 23, 2006 7:29 pm ]
Post subject: 
Quote:
Certainly could be the tires. I bought a truck and couldnt go more than 35 or it would rattle you to death.
Try them first and then if it doesnt fix ask the Forum again :)
frank

The tires need replaced, so there's no arguing that....but the only thing that leads me to believe it's not the tires, is that I don't get the shaking as long as there is a load present. I got up to 55mph no problem, it's just that 10mph range, and only when there isn't a load. Crazy! I will definately replace the tires, and I hope that will correct it. Thanks for your input!
Author:  pushitonme [ Mon Oct 23, 2006 7:36 pm ]
Post subject: 
Quote:
H'mm. Could be a driveline balance issue, a rear axle pinion angle issue, an engine/trans mount issue...

Well, since I'll be swapping out the blown engine soon, that should take care of any engine/trans mount issues. I'm thinking it's probably that small dent in the driveshaft, which would cause a driveline balance issue...right? I was just kind of hoping I wouldn't have to replace the driveshaft over such a small ding. Oh well, such is life huh? If you guys only knew what I've been going through with this truck, ever since it came to me. Then again, most everyone here has been doing this far longer than I, so I'm sure you can imagine. Thanks again Dan, let me know if you think of anything else.
Author:  SlantSixDan [ Mon Oct 23, 2006 8:11 pm ]
Post subject: 
Oh, I doubt you'll have to replace the driveshaft. You may want to try putting a screw-type hose clamp over the driveshaft, with the screw and retainer assembly (the heavy part of the clamp) directly atop the dent, and see if this changes the vibration. It probably won't fix it, but if you experience a marked change, you know you're on the right track.
Author:  Ron Parker [ Tue Oct 24, 2006 3:46 pm ]
Post subject: 
What input shaft bearing are you talking about rearend or transmision. Also did you check the trans output bearing. Thanks Ron Parker :D












It Aint Over Until I Win
Author:  pushitonme [ Tue Oct 24, 2006 4:18 pm ]
Post subject: 
Quote:
What input shaft bearing are you talking about rearend or transmision. Also did you check the trans output bearing. Thanks Ron Parker :D


I replaced the one at the rear end. I didn't even think about checking the trans output. Thanks! I'll definately check that out. I guess I just didn't think it would be a bearing, 'cause there's no grinding, but you're right, I guess it could be. When I find an engine and do my swap I'll check it out and post the results. In the meantime, any other ideas are always welcome. Thanks!
Author:  pushitonme [ Tue Oct 24, 2006 4:20 pm ]
Post subject: 
Quote:
Oh, I doubt you'll have to replace the driveshaft. You may want to try putting a screw-type hose clamp over the driveshaft, with the screw and retainer assembly (the heavy part of the clamp) directly atop the dent, and see if this changes the vibration. It probably won't fix it, but if you experience a marked change, you know you're on the right track.

Another good idea! Thanks!
Author:  Ron Parker [ Tue Oct 24, 2006 5:55 pm ]
Post subject: 
I have a question for you why do you put your transmision in neutral to slow down. This come up on another post. I have driven several different straight shift cars and trucks in my life and have never done this. The last Dodge i had was a 79 Ramcharger I bought new 4wd with a 4 speed. It Was a sweet ride kept it for 13 years and never replaced clutch or drive train parts. In 35 to 45 mile trafic slowing down i would push the clutch in and slow down and when i got stop put it in first. Sold the Ramcharger in 92 with 89 thousand miles on it with the same clutch presure plate. The person i sold it to put another 15 thousand miles on before he had to put a clutch in it. Am i missing something Thanks Ron Parker :D



It Aint Over Until I Win
Author:  pushitonme [ Wed Oct 25, 2006 4:43 am ]
Post subject: 
Quote:
I have a question for you why do you put your transmision in neutral to slow down.

I don't. Usually when I'm coming up to a stop, I either downshift, or hold the clutch in and slide it in to first while I'm still moving as I get closer to stopping. My foot keeps the clutch in the whole time I'm stopped, unless I'm at a super long red light, in which case, yes the tranny goes to neutral and my foot comes off the clutch.

I just used the phrasing to get my point across that the shaking occurs when drive is disengaged. In my mind, holding the clutch in is just like having it neutral, it's the same outcome anyway.

Thanks!
Author:  Jeb [ Wed Oct 25, 2006 8:06 pm ]
Post subject: 
I wouldn't downshift to first at anything above walking speed. That is rough as hell on the synchros unless you double clutch. Also I would pratice rev-matching on downshifting instead of pushing in the clutch and coasting to a stop. Try to keep the transmission engaged most of the time so you can react quickly if you need to take off and get out of the way.

I rev-match and downshift in my Miata whenever I come to a stop. It saved my but one time. I was slowing down for a stop light and had just shifted down to second and was about to stop. I looked behind me and saw a woman in a SUV yapping on a cell phone. I noticed she wasn't slowing down and was going to hit me. I floored it and blew through the red light and turned out of the way. The woman slammed on brakes at the redlight and slid right into the space where I was previously sitting.

Of course, a pickup with a stock slant is not going to be as snappy as a Miata but always being ready never hurts.
Author:  pushitonme [ Thu Oct 26, 2006 4:49 am ]
Post subject: 
Quote:
I wouldn't downshift to first at anything above walking speed. That is rough as hell on the synchros unless you double clutch...

It never goes into first until I'm almost completely stopped. It's just always felt smoother to me to slide it in to first when the vehicle has a slight roll. Usually I hold the clutch in and move the stick through 3rd, then 2nd, sometimes I engage the gears to slow down, and sometimes I just use the brakes. But I'm always in position so that if anything happens, all I have to do is lift one foot up and slam the other on the accelerator.


As far as rev matching goes, I used to do this in my '81 Datsun Pickup all the time. It wasn't as easy in my '90 S-10, so I didn't use the technique as much. I haven't really tried it in the mazda protege I drive, or my fiance's '95 saturn sc2. And I definately haven't tried it in the Puterd, for obvious reasons. I have never really had clutch problems before, granted, I've never really owned any of my vehicles for more than three or four years, but obviously I'm not tearing through clutches with the way I drive. I've known people who were so hard on their cars that they had to replace the clutch just about every 1 to 2 years. Crazy!

So is rev matching supposed to be easier on the tranny? Or is it just something to help prolong the life of your clutch? Always interested in learning new things. Thanks!
Author:  Ron Parker [ Thu Oct 26, 2006 5:11 pm ]
Post subject: 
Guys i did not mean to open up a can of worms just i seam to remember this came up on another post. Getting to the viberation problem is what we want to fix. Thanks Ron Parker :D










It Aint Over Until I Win
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