Drivetrain Alignment

[Bill75]

I'd like to check the tailshaft/pinion alignment but I'm a little confused on the proper method to do it. I've read several papers and I understand the 3 deg max angle and that the centerline of the pinion and the centerline of the transmission tailshaft should be parallel but I don't understand what to use as a "0" reference point to check the angle of each of the parts. Some papers refer to using the starter housing but it would have the same angle as the tailshaft.
Also, what if the pinion angle is wrong, is there any way to adjust/shim it?

 

[Vettehead Mikey]

This won't answer your question but to save you a lot of trouble- unless you've made some serious mods to the car or are trying to deal with a previously bent frame, it's probably not worth the bother of checking.

There's no practical way of changing the differential angle, and if your engine and transmission are sitting on stock (or stock type) mounts, then you'll be well within the acceptable range.

 

[gmjunkie]

This won't answer your question but to save you a lot of trouble- unless you've made some serious mods to the car or are trying to deal with a previously bent frame, it's probably not worth the bother of checking.

There's no practical way of changing the differential angle, and if your engine and transmission are sitting on stock (or stock type) mounts, then you'll be well within the acceptable range.

You are 100% right!!

 

[Bill75]

This won't answer your question but to save you a lot of trouble- unless you've made some serious mods to the car or are trying to deal with a previously bent frame, it's probably not worth the bother of checking.

There's no practical way of changing the differential angle, and if your engine and transmission are sitting on stock (or stock type) mounts, then you'll be well within the acceptable range.

Yes, everything stock and the car has never been hit but I've had this damn vibration issue that only appears under throttle and just slightly at cruise speed 60-70 mph under throttle. New engine, motor mounts, u-joints on half shafts and drive shafts, had the driveshaft balanced, etc. It's driving me nuts. I'm about to put in a TK0-500 and thought this would be the perfect time to check it out.

 

[gmjunkie]

Did you get the yolk on the drive shaft or one of the ends on the half shafts 180 deg out??

 

[Bill75]

Did you get the yolk on the drive shaft or one of the ends on the half shafts 180 deg out??

I marked the shaft front/rear before I gave it to them for balancing. It is possible that the previous owner might have reversed it though for some reason. The transmission has been out before.

Is there any way to tell which direction it was intended to be installed? If I remember the counterbalance was towards the end that's closest to the transmission.

 

[craig32]

Hey Bill,
Mine does that too, I have a (at least one) bent wheel. Have you had it aligned recently or had your tires balanced?

 

[GerryLP]

....only appears under throttle and just slightly at cruise speed 60-70 mph under throttle....

That is the problem I have been trying to resolve lately. It appears to be some sort of resonance vibration between 60 and 70 miles per hour. I have swapped the drive axle's position in reference to the yoke at tranny and at differential as well.

I am hoping that the 155k miles on the Vette is not the reason for the rear spindle arm assembly bearing going bad on either side or both :W :ugh :cry ad .

GerryLP:cool

 

[Bill75]

Hey Bill,
Mine does that too, I have a (at least one) bent wheel. Have you had it aligned recently or had your tires balanced?
Yes, I've done that also. I've had the bearings replaced in the rear end also. It's really throttlle/power related, no vibration with the clutch in and reving the engine or coasting.

That is the problem I have been trying to resolve lately. It appears to be some sort of resonance vibration between 60 and 70 miles per hour. I have swapped the drive axle's position in reference to the yoke at tranny and at differential as well.
Sounds like the same problem. Do you have a 4 speed or auto?? I'm thinking maybe it's the mainshaft bearings in the transmission or something. It's pretty quiet though with the car in neutral, maybe just a slight bit of sound.

Bill

 

[gmjunkie]

Hey Bill,
Mine does that too, I have a (at least one) bent wheel. Have you had it aligned recently or had your tires balanced?
Yes, I've done that also. I've had the bearings replaced in the rear end also. It's really throttlle/power related, no vibration with the clutch in and reving the engine or coasting.

That is the problem I have been trying to resolve lately. It appears to be some sort of resonance vibration between 60 and 70 miles per hour. I have swapped the drive axle's position in reference to the yoke at tranny and at differential as well.
Sounds like the same problem. Do you have a 4 speed or auto?? I'm thinking maybe it's the mainshaft bearings in the transmission or something. It's pretty quiet though with the car in neutral, maybe just a slight bit of sound.

Bill

If you've done this(I have swapped the drive axle's position in reference to the yoke at tranny and at differential as well.)I would check exhaust system to make absolutely certain it's mounted securely (and not barley rubbing and is mounted in all the hangers properly,tail shaft bushing in transmission and take the car to a Tire shop that has a Hunter 9700 Road Force tire balancer!!!! Road Force Balancing makes a Big,Big difference in vibration at Highway Speeds and Under Power!!! The first thing I do to a Vette or any other vehicle when I buy it to Resale or drive is Road Force Balance!!! It has Saved Me Thousands of $$$ in Time and Part's chasing a Vibration!! All Tires and Wheels have some run out, and a technician that knows what he is doing on a Hunter 9700 will turn the tire on the wheel to Compensate for the run out on tire and wheel,and it usually takes allot less weight to balance the tire!!!!!!!(the Balancers Computer tells him how far,which way,how much and actually puts 750-850 lb of rolling force on tire while balancing!!)

 

[JohnZ]

Go to www.gsp9700.com and you'll find a locator feature that will tell you the nearest shop/dealer to you that has a Hunter GSP-9700 machine; it will spot lateral and radial wheel and tire runout, unloaded and loaded (road force variation), a/k/a "smooth road shake". Ordinary spin-balancing only balances the assembly, which is only half the job - a square wheel can be perfectly spin-balanced, but won't run smoothly on the road. Even a perfectly round tire in the free state can have road force variation under load due to internal construction variations which cause the carcass to be stiffer in one area than another.

Our local Chrysler dealer has a Hunter GSP-9700 (none of the local tire shops do), and that's where I take all my cars for wheel balance.

 

[GerryLP]

...Sounds like the same problem. Do you have a 4 speed or auto??
Bill

Bill,

My Vette has the original TH-350C in it. The tranny underwent one early repair and later one overhaul. For the overhaul, I purchased the Ecklers kit with the whole kit & caboodle. That included an overhaul of the lockable torque converter as well.

The last thing (grasping straws here...:ugh ) I had done on the car was not stock per-se because I was having a hard time locating the proper hanger clamp for the rear "Y" pipe (in the mean time I had used a steel strap with NO rubber hanger to hold it in place), so I though that vibrations were transferring that way, but I finally found the correct hanger clamp together with a new rubber hanger, and it is still doing the same.

So it does it with a 4 speed manual as well....hummm... You said that your trailing arm bearings are new as well?

Gerry:cool

 

[GerryLP]

Go to www.gsp9700.com and you'll find a locator feature that will tell you the nearest shop/dealer to you that has a Hunter GSP-9700 machine; it will spot lateral and radial wheel and tire runout, unloaded and loaded (road force variation), a/k/a "smooth road shake". .

JohnZ,

I for one thank you for the tip. There appears to be several shops here in town with that machine together with the "StraightTrak LFM" feature.

I have 275/60R15's in the rear and 255/60R15's in the front, so maybe this combination requires a sophisticated balancing machine to correct it.

GerryLP:cool

 

[gmjunkie]

Go to www.gsp9700.com and you'll find a locator feature that will tell you the nearest shop/dealer to you that has a Hunter GSP-9700 machine; it will spot lateral and radial wheel and tire runout, unloaded and loaded (road force variation), a/k/a "smooth road shake". Ordinary spin-balancing only balances the assembly, which is only half the job - a square wheel can be perfectly spin-balanced, but won't run smoothly on the road. Even a perfectly round tire in the free state can have road force variation under load due to internal construction variations which cause the carcass to be stiffer in one area than another.

Our local Chrysler dealer has a Hunter GSP-9700 (none of the local tire shops do), and that's where I take all my cars for wheel balance.

That's the Baby there!!!! Makes a Big,Big difference don't it John??

junk!!

 

[Bill75]

You said that your trailing arm bearings are new as well?
Gerry:cool

Trailings Arms are new and all associated bearings, also stub axles and yoke bearing.

John/Junk......thanks for the info and the link on the Hunter equipment. I found several shops here locally that have it. Honestly though, I'm having a hard time relating tire balancing to this problem. At 65 mph with the throttle on, the vibratioin is present. If I remove the throttle it disappears instantly. If I depress the clutch and rev the engine while coasting it's not there, If I put the car in neutral while coasting (still at highway speed)and rev the engine, it's not there. But put the car in gear and apply power and it's there. I don't really feel it in the shifter it's mostly a seat of the pants vibration.

I'll see about balancing the tires this week.

 

[JohnZ]

Trailings Arms are new and all associated bearings, also stub axles and yoke bearing.

John/Junk......thanks for the info and the link on the Hunter equipment. I found several shops here locally that have it. Honestly though, I'm having a hard time relating tire balancing to this problem. At 65 mph with the throttle on, the vibratioin is present. If I remove the throttle it disappears instantly. If I depress the clutch and rev the engine while coasting it's not there, If I put the car in neutral while coasting (still at highway speed)and rev the engine, it's not there. But put the car in gear and apply power and it's there. I don't really feel it in the shifter it's mostly a seat of the pants vibration.

I'll see about balancing the tires this week.

Well, that's a much better description of the symptom - it's torque-related, not speed-related. I'd take a good look at the bushings and through-bolt where the diff nose bracket bolts to the frame; when those bushings deteriorate, it'll cause exactly what you describe. The bracket can go metal-to-metal at the frame, transmitting vibration, and it also allows the nose of the diff to rise enough that the rear driveshaft U-joint can contact the top of the tunnel.

If they're shot, replace them with the OEM rubber ones with the molded-in centering sleeve for the bolt; the "poly" replacements are too thin (raises the nose of the diff) and they don't have the centering sleeve (allows the bolt to touch the edge of the holes).

 

[Bill75]

Sorry about my poor initial description, thanks for the tip on the bushing. I replaced it a little more than a year ago when I did the trailing arms etc. BUT, I don't remember what the center hole construction was and also I remember just tightening the bolt up until I had a little compression on the rubber. Maybe I should have torqued it????????
I'll jack the car up tomorrow after work and check it out.

Thanks

 

[lone73]

Bad Vibe's

I had a similar vibration in my '73 4spd. Never really worried about too much since its an old car and used to be my daily driver. When I rebuilt the halfshafts I did have them dynamically balanced. Tried a few other things like you did, nothing made a difference. Summer of '05 I rebuilt the transmission with all new bearings and few other new parts. Now its smooth as glass, new car smooth in fact and I know I have a slightly bent wheel. When you stab your new transmission in there it could very well solve your problems. My guess is that most of the vibe's were coming from the slop in the tailshaft bearing inside the back end of the transmission. It isn't extremely difficult to replace on a Muncie 4 spd. I also installed a new tailshaft so that all clearances were back to new. I had suspected that was the prob. Heard of it before.
good luck with it
.
.
.

 

[Bill75]

Hi Lone, thanks for the insights. If I find the bushing John mentioned is in good shape and I installed it correctly, then it would seem the transmission might be at fault. There seems to be a lot of folks out there with this nagging situation. I love driving the car but on a long trip I wish I'd left it home, if this problem is still there after I put this transmission in I'm going to check myself into a home somewhere.
I'll post what I found tomorrow. Thanks

Bill

 

[Bill75]

John,

I checked the rubber mount and it looks OK, doesn't appear to have been moving around, you can see some compression in the rubber. Also called the Vette shop wgho sold me the part and verified it was OEM type. I actually have the old one still and can see what you mean about the sleeve inside. How does it look to you?