Hi guys,

I've had no luck on the Transmission board and am posting this here in case it might be torque arm or pinion angle related. I have a Spohn Torque arm and all Spohn chassis/suspension pieces. The pinion angle was set correctly when the parts were installed less than a few thousand miles ago.

We've just fitted a ZZ4 Crate Engine into my 1989 TransAm GTA and need some advice. This problem was there before the new engine so is definitely not related to it.

There is a pulsing rhythmic vibration which begins quitely from 3000rpm, building with increasing revs and speed. After 4000rpm it becomes much more violent and loud. It sounds as though it is coming up through the centre/front of the transmission tunnel.

It is rev related rather than speed so I don't think wheel/tyre balancing is an issue. I can easily check this though, even though it was only done a few thousand miles ago.

I think the same vibration might be there to a tiny extent when revs are applied in neutral, but am not certain. When you change into neutral on the highway when the vibration is happenning it goes away, but I think that is due to the revs dropping down.

Could this be driveshaft imbalance? Worn UJ's? Wheel imbalance? Automatic transmission problem? Torque convertor problem? Are there shafts/bearings related to the box that could wear or become loose to cause this symptom? Torque arm pinion angle incorrect? Rear end issue? What do you guys think seems the most likely cause for the problem?

We are planning to get the car up on axle stands next week and get a look around.

I've bought new front and rear UJ's to fit and also plan to send the driveshaft off for dynamic balancing.

Any comments or suggestions would be welcome.

Dr G

 

89's had a problem with driveshaft imbalance. My 89 IROC has a similiar vibration. Most guys on here replace their driveshaft with an aluminum one. I have seen them here in the Parts meesage board frequently. Hope this helps.

 

The car has the factory aluminum driveshaft, which looks in good condition. As I said above though I have new UJ's which I'll try, and also plan to sent the shaft away to check the balancing.

 

Sounds all to familiar to this thread........... https://www.thirdgen.org/forums/tran...vibration.html

 

If it goes away in neutral on the highway it probably isn't your driveshaft or u-joints because those are still spinning on the highway. I had a shaft imbalnce on my car and and bad u-joints and it remained when I disengaged the clutch on the highway.

But then it would vibrate when reving the engine without driving.

Seems to me it may be a load only thing. Get the new u-joints and then get the shaft balanced anyway since you bought them to eliminate that area.

You have to narrow it down to engine or tranny or driveline.

 

if its a stick shift then it is probably your pilot bushing, between the motor and trans... mine went twice well just got a little worn and let the input shaft get sloppy if im goin down the highway and rip to 70 mph it would be there but if i let out the clutch and then let go it would usually line up agagin and stop...

 

Drex, it is an auto TH700R4.

 

I'd lean more towards DS imbalance or u-joints.
You have a factory AL shaft? Does that come with a small vibration dampener like the LS1's? I have a 2000 TA DS on mine with a small harmonics balancer. That thing has been quiet up to 142mph.

 

I too would say that it's not ds balance if it goes away when in neutral. A shaft vibration wouldn't vary with engine rpm, only with speed. It could still be a u-joint, as they may only vibrate under load. Another check would be the pinion bearing. It could also spin freely when spun from the gear side, but vibrate when under load.

Have you check everything under the car? Recheck/tighten all nuts and bolts? Check for ds slack in the tailhousing of the trans? Pinion bearing slack?

If the pinion angle is not excessive, then it shouldn't be the problem. The spohn tq arm may be causing this vibration to transfer into the car worse, but it would not be the cause of the vibration.

 

Can you guys explain why it would not be the U-joints if the car is in neutral on the HWY? I dont see how this would make a difference since the driveshaft is still spinning. Not trying to be an a**, just asking as I dont understand.

 

Viprklr:- Yep, stock aluminium driveshaft. I don't think it has any fancy balancer, just the factory stick on balance weights.

Only had time to get the car on stands, change the oil and check the convertor balance weights yesterday. I'll get back under and check everything else as soon as I can. I'll update the thread to let you guys know how I get on.

 

Okay, heres the update!

The vibration does NOT occur at all in neutral or park.

I removed the driveshaft, checked the balance weights were still there. Fitted new properly lubricated U-joints.

I reset the pinion angle to -1 degrees. Tightened up my adjustable LCA's, one nut was slightly loose.

Went for a drive and the vibration is still there but has changed slightly as regards when it occurs. Now under full throttle the vibrastion doesn't really appear until AFTER 4000rpm and by 5000rpm gets as violent and loud as it used to be at 4000rpm. It seems more prominent on part throttle loads and on part throttle is noticeable after 3000rpm.

Could I be dealing with more than one cause here? I'm encouraged that changing the pinion angle has changed/improved it. Perhaps I've set the pinion angle better than before but still not correctly so I'll check that again in a few days. I haven't had the driveshaft balanced yet, so I can still do that. I may be able to source a loan of a stock torque convertor to try, but it's a lot of work to swap it in and out and it might not help.

Any ideas or comments are much appreciated.

 

this is interesting. im experiencing the same vibration. i also have a spohn torque arm. i figured it was just because i had a set of older tires that probably went out of balance. its like a rythmic throbing, i think our settings on the pinion angle may be wrong. causing a slight binding. if you have your installation instructions, it warns you to go no farther than what they recomend, i wonder if their estimates are just a little off......

 

This linked thread and pics describes the exact way to set the pinion angle, and I have followed these instructions exactly.

Spohn TA pinion angle verification
https://www.thirdgen.org/forums/susp...ion-angle.html

Angle Pic 1
https://www.thirdgen.org/forums/atta...nion-angle.jpg

Angle Pic 2
https://www.thirdgen.org/forums/atta...on-angle-2.jpg

I also used this guide:-
http://www.wolferacecraft.com/pinionangle.aspx

 

What are the angles you measured?

Between the trans and d/s and

between the d/s and rear?

I would get your d/s balanced just to rule it

 

FWIW: Well I am not really good at this, but a did I a burn out one day on rough concrete, and bent the aluminum driveshaft. My driveline vibration would come in nearing 70mph on the xway.

Or it could be something simply like tire/wheel balance. If I have a tire/wheel assembly out-of-balance by 3/4 oz., I can feel it.

 

If it were tire or ds balance it would be very odd if it went away when in neutral, and it would come and go with tire speed, not engine rpm.
Since you have also changed engines and still have the same issue, I would assume something trans/converter related.

As for not being the u-joints in neutral on the highway, depending on how they're worn, they may only vibrate when under load. There's no load in neutral. - He has ruled this out, and again, it would usually come as related to speed, not engine rpm.

 

Hello again,

Here's the update.

I've checked the pinion angle again, adjusted it with the appropriate instructions. Went for a drive. No change.

Checked the adjustable panhard rod location, properly centered. Went for a drive. No change.

Turned the driveshaft 180 degrees in terms of location at the rear end. Went for a drive. No change.

Checked the tranny fluid level. Found it to be a little high. Drained it down to the max level. Went for a drive. No change.

I ran the engine up to 4500 revs with the driveshaft disconnected and there was no vibration. However, I don't think that helps at all as the engine is not under load, neither are the driveline angles etc.

The driveshaft is now off and being delivered to the engineering shop tomorrow. That allows me to rule it out 100%.

After that I'm looking at going to a local Auto Transmission specialist to see what they say. Pay them for the (suggested) diagnosis, then order the parts from the States myself. I'm now pessimistically thinking that it's definitely the torque convertor or transmission that's gone.

I'll keep the thread updated as to how I get on. As always, any comments, suggestions or ideas are very welcome.

 

Just remembered a wacky one a mechanic created that caused a vibration. He changed my rearend fluid without adding the proper additive for the limited slip. I went a week with it before I figured it out. Just thinking outside the box a bit...Also, is the car lowered? A vibration can be caused by the pinion and the driveshaft not being parallel to each other but too much in line. Sometimes a spacer at the tranny mount can raise it enough to create a parallel situation.

 

How about a bad or lose touque arm mount at the tranny ???


If it's rubber it might be too worn out. If the "connecting" bolt is not tight you will feel a vibration. If you swapped to a Poly Bushing than you probably drilled out the rivets holding the rubber bushing in place so you could install the POLY,........ be sure the new hardware doesn't allow the new bushing ANY play or slack.

Vibration problems SUCK !!! Usually, All you can do is start at the rear wheels and work your way back towards the motor till you find it !

 

Crimson, many thanks for the reply! I haven't changed the rear end fluid in a few years, so that's another job on my to-do list.

The car is lowered with Eibach springs. The pinion and driveshaft angles have been adjusted to spec with my Spohn adjustable torque arm.

 

John, thanks for the reply! The tranny mount is poly, installed 2 years ago along with new Spohn crossmember, torque arm, LCA's, LCARB's, panhard rod, Koni Yellows, Eiback springs, adjustable top mounts etc. The mount looks in good condition and theres no slack in the bolts.

Vibration problems are truely awful aren't they?

 

I took the driveshaft to a local engineering shop last week for balancing, complete with the trans output shaft and both UJ's. They said they couldn't balance it as there was 'no yoke at the rear'. I explained that the other end is bolted onto the rear end and to give them anything else would mean taking the rear end apart or giving that to them as well. They said all they could do was check the shaft for trueness - so they did that and said it was only 0.001" out at the rear and 0.002" off at the front. They felt this was within tolerance levels and unlikely to be causing the vibration.

I went to the best auto transmission rebuilders in my area yesterday to get their advice/help regaring the problem. They went for a drive with me and then put the car up on their ramps and say they feel that it is unlikely to be related to the transmission or convertor.

They pointed out 2 points where my true dual exhaust system is too close to the body. Also, they noted the Spohn crossmember sits virtually against the transmission oil pan.

The next thing for me is to address these areas and take things from there.

 

Well I've modifed the passenger side exhaust system now. Several areas have been massaged with a ball peen hammer and the whole thing has been mounted more sercurely and isn't touching the body/chassis now. But.... the vibration is entirely unchanged.

 

Dont know if this has been mentioned. Dont over tighten the bolts on the u-joint. They only need 15-20 ft. lbs. of torque. Any more and you will bind the caps and the bearings wont spin. Wont take long to eat the shaft on the u-joint. This will cause you some drivability problems.

 

We just got our IROC back on the road after sitting for three years and now I have some vibrations at about 70. I pumped up my tires during storage to about 40-50 pounds to eliminate the flat spots, but it feels like the driveshaft is out of balance. I am going to add an aluminum driveshaft to my Christmas list. Keep us posted on what finally solves yours.

 

your ds shop sucks. There's no reason a shop can't spin balance a shaft w/o the rear yoke, how would places like inland do it? The run-out doesn't sound bad to me though.
The part that's really throwing me is that it seems to be rpm related, not speed. The ds, axles, etc all continually spin faster as speed increases, and they all keep spinning even when in neutral.
I got one for ya, any engine accessory mounts loose? Maybe a left out brace bar for the a/c compressor? - I had the alternator/pwr steering bracket come loose once and I thought I had munched something in the trans. Pretty decent vibration.

 

Shagwell, I'm still worried that the rpm related nature might be pointing towards transmission/convertor.

The engine accessory mounts are all solid. The problem was there before the old engine went, and has been there since despite te engine swap.

I removed the AC when the engine was out and am using a delete pulley. I'm also running a delete/idler pulley where the smog pump used to be.

I will double check the torque/tightness of the brackets and bolts when I'm next working on the car. Thanks!

 

Hey let me know if you get it fixed. i've had the same exact problem since i bought my 87.

the motor, trans and rear have been changed so has the entire rear suspension and trans mount.

i've been reading on this subject on the board and see that it's pretty common problem that i dont think anyone has fixed.

i was thinking maybe wheel bearing or motor mounts but who knows

 

Dr.G,

When you replaced the old engine with the ZZ4, did you use the same harmoinic balancer on the new motor? or did the ZZ4 come with its own balancer.

I have had the same type of vibration several times in the past and it is commonly mistaken for a u-joint and such when in accuallity it is engine related problem with the harmonic balancer.

Signed,And old V6 friend.

 

BobbyZ: - The motor mounts are new poly ones, the vibration was there with the old rubber ones also. I haven't changed the wheel bearings but may try it.

Duracell Bunny: - The ZZ4 came with it's own new harmonic balancer. The vibe was there with the old engine and old balancer in the same way. Old V6 friend - I tried to send you an email on the account you used a few years back. Any chance of emailing or PM'ing me?
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Heres the latest.

I loosened the Spohn transmission crossmember and the torque arm, and was able to adjust it so that there is no interference between the transmission oil pan and the crossmember - it's all been straightened up. I then checked and reset the pinion angle.

I took the car out and the problem is still there, but I now think I can feel/hear it in neutral when I rev the engine up.

I think I will try to find a different set of engine pulleys to 100% rull them out, and then go back to the transmission shop.

As always, all comments and suggestions are welcome.

 

Gordon (I think it's Gordon, if not then my appologies),
First off its Sakeed123@aol.com . You can always reach me there.

Above you have stated it is rpm related and comes on about 3K and get violant at 4K. That would not be anything after the trans to be rpm related. Anything after the trans would be speed related just to rule out the obvious.

Potential causes: (Now I know some of these do not make sense because you stated it occured befor the motor swap also- but some could have been overlooked-
Cracked flexplate
Loose or missing bolts from the flexplate
Wrong flexplate (ie internal balance unit on an external balance motor)
Too small of a balancer/ or bad balancer
Motor and trans not properly seated
if the tranny is going out- unfortunately you will find out very soon

I hate to say it, but it is definately something up front. You are not running solid mounts or a motorplate are you. Because if you are then that could be tranfering massive motor vibration.

 

'I hate to say it, but it is definately something up front. You are not running solid mounts or a motorplate are you. Because if you are then that could be tranfering massive motor vibration.'

Nope, polyurethane engine mounts. Was happenning with the old stock rubber engine mounts before the swap.

I'm very suspicious also about trans and TC. I will check the engine pulleys and swap them back to standard to see if that helps, and then get back to the trans shop for them to take a look at it.

Many thanks for evryones helps and suggestions. I will keep the thread updated as things are tried and when this is all sorted.

 

Is the trans centered on the crank?

I know how to check it with a stick, but not with an auto. I think I have been fighting the same problem as you, but have not gotten of my *** to pull the trans and see if the bellhousing is centered on the crank centerline. I have no clue as how to do it with an auto but it is a possibility.....

 

Well guys I replaced the torque convertor and the major vibration/harmonic is now cured. Their are still numerous trim rattles but they will be dealt with in due course.

The problem now is the lack of traction and the car kicking sideways at highway speeds when you go past half throttle. The increase in low down torque with the higher multiplication/higher stall convertor is phenomenal. God it feels good to be driving a healthy V8 again.

Thanks to all of you for your help, suggestions and encouragement!

 

That's good news. At least you have the option of driving your healthy V8 right now. I'm currently in the process of getting 4-8 MORE inches of snow.