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83 T/A with the original 305 and 5 speed.
Get a vibration right at about 60mph, kind feels like running over the rumble strips at the edge of the highway, but maybe half as intense. From 60-80 its there, but doesnt increase in intensity with speed, didnt push it over 80. Not violent or anything, could drive with it if you had to, but very annoying. If i had to guess, feels like under my feet, closer to the trans than the rearend, but again, thats just guessing. Varying RPMs doesnt change it, neither does putting the clutch in or dropping it into neutral.
It has new rims and tires, and 1.25 drop springs all around. It kind of always vibrated at this speed, but has gotten worse lately.
Replaced the original UJoints, and had the driveshaft balanced. Driveshaft shop said it was way out, and added weights, didnt seem to help.
New wheels and tires mean nothing.
You should first move everything front to rear and rear to front and see if there are any changes.
if you have a buddy with a similar vehicle, swap and see if anything changes.
Take the car to a tire shop, have them put the wheels and tires on the machine, and see if you have an out of round condition or wobble. If not, have them "road force balanced."
All that being said, you could still have internal tread separation, even if the tires are new.
New wheels and tires mean nothing.
You should first move everything front to rear and rear to front and see if there are any changes.
if you have a buddy with a similar vehicle, swap and see if anything changes.
Take the car to a tire shop, have them put the wheels and tires on the machine, and see if you have an out of round condition or wobble. If not, have them "road force balanced."
All that being said, you could still have internal tread separation, even if the tires are new.
Fair point. Cant swap front to back, but im gonna get it up to the tire shop and have them check and rebalance the wheels. At least mark that off the list as well.
First question, that nobody ever seems to think about answering, even when asked:
Is it at drive shaft speed? As in, hmmmmmmmmmmmmmm no matter what the engine is doing
Or is it at engine speed? as in, hmmmmmmmmmmmmm until you take it out of gear and let the engine idle, at which point it shuts up
Or is it at wheel speed? wubba-wubba-wubba-wubba-wubba
If it's at wheel speed, have you tried swapping wheels around and see if it moves? If it's at drive shaft speed, what transmission is in it?
In a word, be LOGICAL about it. Don't just talk about how you busted out the parts cannon and blasted a broadside at the car.
First question, that nobody ever sems to think about answering:
Is it at drive shaft speed? As in, hmmmmmmmmmmmmmm
Or is it at engine speed? as in, hmmmmmmmmmmmmm until you take it out of gear and let the engine idle, at which point it shuts up
Or is it at wheel speed? wubba-wubba-wubba-wubba-wubba
If it's at wheel speed, have you tried swapping wheels around and see if it moves? If it's at drive shaft speed, what transmission is in it?
In a word, be LOGICAL about it. Don't just talk about busting out the parts cannon and blasting a broadside at the car.
Thanks for the questions to get me thinking.
Its definitely not engine speed. When its happening at speed, taking the trans out of gear, idling the engine, racing the engine, makes no difference to the vibration.
Its the stock T5 5speed manual.
Hard to say driveshaft speed vs wheel speed. It sounds exactly like running over rumble strips at the edge of the highway lanes at 70mph. A fast Br-Br-Br-Br-Br noise.
Drive shaft speed = the same as engine speed in 4th gear
Wheel speed = about 1/3 to 1/4 of that
"Hmmmmmmmmmm" vs "wubba-wubba-wubba-wubba-wubba" (both kinds often not constant, but rather sort of pulsating)
Brrrrrrrrrr sounds more like drive shaft speed
How tight is the drive shaft in the trans ext housing bushing?
You DO know of course, that the factory drive shaft yokes - BOTH ends - are not equipped with ANY method for centering the U-joint trunnion, right? Meaning, there's no guarantee that the U-joint is centered in the yoke ears at all. The factory originally used a groove in the yoke and a groove in the U-joint cap, filled with plastic, to retain the caps; there is NO PROVISION WHATSOEVER for seating the inside clip retainer in the proper place. That "feature" of the yokes, ALL 4 of them, is not machined. The ones going into the trans and the one on the rear are usually the worst.
Last edited by sofakingdom; Nov 7, 2023 at 05:24 PM.
Drive shaft speed = the same as engine speed in 4th gear
Wheel speed = about 1/3 to 1/4 of that
"Hmmmmmmmmmm" vs "wubba-wubba-wubba-wubba-wubba" (both kinds often not constant, but rather sort of pulsating)
Brrrrrrrrrr sounds more like drive shaft speed
How tight is the drive shaft in the trans ext housing bushing?
You DO know of course, that the factory drive shaft yokes - BOTH ends - are not equipped with ANY method for centering the U-joint trunnion, right? Meaning, there's no guarantee that the U-joint is centered in the yoke ears at all. The factory originally used a groove in the yoke and a groove in the U-joint cap, filled with plastic, to retain the caps; there is NO PROVISION WHATSOEVER for seating the inside clip retainer in the proper place. That "feature" of the yokes, ALL 4 of them, is not machined. The ones going into the trans and the one on the rear are usually the worst.
I would definitely say more hmmm than wubba.
Yea, i took my time to make sure the ujoints into the rear were nice and even centered. The fronts as well, plus the fronts were spun up at the driveshaft shop, so they should be in spec. The shaft into the trans housing bushing feels tight, no play there.
make sure the ujoints into the rear were nice and even centered
How?
It's not possible. The places where the C-clips end up sitting against, are not machined. They're the raw forging. Half the time, they're not even the right distance apart. Usually too far apart. As an example, on my truck, I had to use a giant C-clamp to gently press the caps together onto the trunnion at the rear end so that the trunnion was secure in the caps, and then it took SEVERAL test drives of gently adjusting the centering of the whole thing (re-applying the C-clamp each time) until it quit humming. The trans end of that particular drive shaft "just happened" to go together reasonably centered but I've had more than my share of vehicles that it didn't.
In my 83 (L69 Z28, T-5 obviously) I also had to have the extension housing bushing replaced with the trans still installed one time... the shop I used had a sort of a puller with thin teeth turned outwards to yank the old one, and a piece of pipe kind of thing to bonk the new one in, to enable doing it without disassembling the trans. Would have been much easier if the trans had been out and apart, butt although I had already done that once when I had it torn down, it wore out again, and needed changed out.
It's not possible. The places where the C-clips end up sitting against, are not machined. They're the raw forging. Half the time, they're not even the right distance apart. Usually too far apart. As an example, on my truck, I had to use a giant C-clamp to gently press the caps together onto the trunnion at the rear end so that the trunnion was secure in the caps, and then it took SEVERAL test drives of gently adjusting the centering of the whole thing (re-applying the C-clamp each time) until it quit humming. The trans end of that particular drive shaft "just happened" to go together reasonably centered but I've had more than my share of vehicles that it didn't.
Factory yokes are CRAP.
This is an interesting thought. I also used a C Clamp to press the caps together and center the works into the rear end and tighten the clamps. Tried to get it centered by eyeball. Maybe instead of that, i need to move it around, drive it and move it until i find the sweet spot.
Maybe instead of that, i need to move it around, drive it and move it until i find the sweet spot.
That's the idea. Mark stuff so you know EXACTLY what you're moving and how much, so you don't end up tail-chasing. It's tedious and kinda dirty, unless you have a pit or a lift (I don't...), but not too "difficult" overall.
That's the idea. Mark stuff so you know EXACTLY what you're moving and how much, so you don't end up tail-chasing. It's tedious and kinda dirty, unless you have a pit or a lift (I don't...), but not too "difficult" overall.
Thats my POA, ill report back with results. Thanks for taking the time to talk this one out.
Just a little update for anyone interested. Spent a few hours yesterday making small changes and driving at speed and noting what helped and what made it worse. Specifically focused on the rear end, since i suspected maybe this was where the issue was. Marking, measuring, writing everything down, then driving and trying again. I got it to a point where the vibration starts at around 65mph, its there but its very mild, went from loud like running over rumble strips when i started this, to now a slight hum. Im gonna leave it there for now, maybe revisit in the future. Its very tedious and time consuming. I wish there was a quicker way. I love this car, but sometimes it fights me.
Too bad the factory yoke isn't built to be serviced... it's the product of a "one way" mind. Put it together once, don't even bother to consider what might happen if it ever has to be serviced. Definitely the mindset of the US automakers during the Malaise years. Replacement ones have machine work to accept the clips.
BTW no endorsement for that source or its products in any way; it just had a good clear photo of what a properly made one should look like. Pretty sure Dorman, Motive, Omix-Ada, etc. are similar in that regard.
