Good afternoon,

I am trying to track down a vibration coming from the whole rear end at high way speeds. I will list what's done to the car below the post because it is not stock.

***EDIT: for what it’s worth I bought the car bone stock and replaced and fixed almost everything in one shot with out driving it, so it’s hard to for me to tell which part made a difference etc as If I installed them 1 by 1

When I would get to 60mph I would start to get a vibration from the entire rear end that you could feel in the entire back end and it does not seem to be coming from a specific side. Its not just a noise but you can literally feel it in the entire rear end/body of the car. After 60 it would get progressively stronger until I get to about 80, and which point I don't really feel comfortable pushing it farther. I was thinking/hoping it was my differential so I swapped it out this weekend with one from a gs300 (3.92 gearing vs the 4.27 from my sc300). This is actually nice because the cruising RPMs are better and it doesn't feel sluggish. Unfortunately after getting everything installed I still have the same vibration. The car has the same symptoms now, however the difference is the vibration starts about 70mph now and gets worse towards about 90 where I stopped. I think this is different because of the different ratio of the GS300 differential. I would think that it could be an alignment or tire issue, but since the symptoms start later in the speedo range now, I'm pretty sure its a drive train issue. It shouldn't be the wheels because they are spinning at the same speed going 60 now as before and now I cant feel the vibration starting at 60 like before. The only things that would be moving at different speeds now are the diff, driveshaft, and transmission output at those new speeds. I don't think its the diff now because both do the exact same thing at different speeds. If I get to speed and the vibration starts, If I let off the gas it continues but slows down as the car drops in speed. The drive shaft is a one piece drift motion 3.5 inch which is supposedly balanced when shipped and the transmission is from an aristo. Anyone have any insights on what I should look at or check? Please see my part/mod list below as I'll list anything that could be applicable or related to suspension or drive line.

95 sc300
-2jzgte aristo swap with aristo auto trans.
-Drift Motion 1 piece 3.5" solid drive shaft.
-GS300 3.92 diff with fresh gear oil and poly bushings.
-All subframe bushings are poly.
-BC coil overs
18 inch wheels.
-All arms/rods/links etc. replaced with Battle Version or FIGS
-3" straight pipe stainless exhaust (bolted straight to car, not with rubber hangers.) I thought maybe the exhaust resonance through the car but when I get to 80 and put the car in neutral, the RPMs drop and its still vibrating

 

after watching this video I’m 90% sure it’s a driveshaft balancing issue. Nothing is loose.

If this is the case to a take it to a regular auto shop or a drive shop place to check/fix the balance? Im guessing they would add weights while on the car?

 

Billy, I think you are right in your assessment that it's due to the 1-piece driveshaft and not whichever diff you used. Although you're probably right that a diff with the higher numerical ratio of 4.272 was causing the d/s to spin slightly faster than it did with the SC400 3.92 diff.

1-piece driveshafts are popular and many people use them on all kinds of builds. I am not entirely sure how the vibrations and harmonics are dialed out with them at very high speeds but I did read about this before ultimately deciding to retain the factory two-piece driveshaft assembly with the factory center bearing isolator. Nearly all OEM setups in rear wheel drive or AWD cars cars, even extreme high performance models, have a two-piece driveshaft with a center bearing that uses a rubber isolator bushing.

The one in the SC/Soarer/MKIV is VERY strong and capable for very high horsepower applications.

With my setup I needed my front driveshaft modified for length or I needed a 1-piece d/s. I stayed with the OEM setup and had the front driveshaft professionally modified to the exact length that I needed in order to fit my R154 perfectly. I'd recommend doing this with whatever OEM Aristo, SC/Soarer or MKIV front driveshaft will work as a starting point for a professional driveline shop to modify at the front shaft only to the correct length needed. It must be a shop that has a two-piece driveshaft balancing machine since re-balancing will be needed.

That being said, Driftmotion makes very high quality parts. Did you order yours in steel or carbon fiber? I have heard that high strength CF 1-piece driveshafts tend to do better with mitigating these high speed vibrations but I am not 100% on that either.

I would venture a guess that at minimum a re-balancing of the 1 piece driveshaft should be done but at the same time this may be a characteristic of getting rid of the two-piece OEM approach with a center isolator.

Many very high horsepower SC/Soarer/MKIV/Aristos all do quite well with whatever combination factory 2-piece-with-center-bearing driveshaft works for their chassis and transmission configurations.

....

Whichever route you choose from here you need to go to a professional driveshaft rebalancing and modification shop that deals with this on the regular. Since you're in Miami and only a two-hour drive away I'll recommend you the shop that I used:

Drivetrain Center
3120 SE Dominica Terrace
Stuart, FL 34997
(772) 203-4442
www-dot-drivetraincenter-dot-info

Very good and skilled people who can handle anything driveshaft related be it 1-piece or two-piece OEM setups. It would be a couple of hours from you in Miami though so maybe an equally good shop is located much closer to you.

Wishing you luck in getting this solved! I know it must be very frustrating after all the work you've put into getting your SC built and finished.

 

Appreciate it! I’m going to see if hopefully it’s something that can be fixed with balancing first and I’ll report back in.

 

That's a good plan! Please do let us know if re-balancing the DM driveshaft cures it!

 

No luck with the drive shaft. Shop said it was pretty straight and only had the very slightest bit on the dial. I had them rebalance it anyways to be sure, but the problem still persists. I also checked the transmission flange and ran the motor with the shaft off to see if it appears to have any play. It seemed dead straight to me as it was spinning.

I also think it seems to start around the same speed as before (60 ish) so I’m thinking the diff and shaft had nothing to do with it. Do these issues seem like they could be a symptom of a tire balancing/alignment issue?

 

Generally shops start w/ a basic tire balance & rotation before diving into the more advanced driveshaft, axle or differential diagnosis. Balance is a cheap & easy way to rule things out.
It is possible the tires are flat spotted depending how long the car sat during the build.

 

^^ Seconding this as well. I did notice that the already old tires of my SC having sat in the same spot in my garage while I worked out my engine swap did not roll smoothly once I got the car on the road again. I tried an alignment and re-checked everything but decided to replace the front and rear tires as a last resort. That seemed to be the problem in my case.

I DID have to get my Supra MKIII R154 front driveshaft worked on and rebalanced a few months later but this was mostly due to it not being a perfect fit in the first place in an SC application (front driveshaft length issue since it was originally from an MKIII Supra and *mostly* worked but not perfectly without shortening it approximately 3/4" for an SC) rather than a vibration issue.

Depending on the quality of the road I am on (some are just not maintained well compared to others) the aftermarket linear rate springs I am running do introduce some driveline oscillations in the worst cases. But it goes away on better roads and that is clearly not your specific issue.

Unless those tires are very new and haven't been sitting for a long time before you've driven on them again Supra Dr may be onto something.

 

I'm thinking this may be right. I’ve put maybe 100 miles on the car and I’ve had the wheels and tires for probably 2+ years now. I’m trying to drive it much more now but it would sit for months at a time with not a lot of miles. It was on jacks a lot at least. Does this deform the tire where it can’t be fixed or can a balance remedy a flat spot? I bought the wheels and tires brand new and had them balanced before I installed them.

I have an appointment at a tire shop tomorrow morning To check and rebalance the tires. If I knew it would sit as long as it would, I would have got the tires towards the end of the car being road worthy.

 

So I went today and had the wheels road force balanced, but the problem still persists. It does seem slightly better but it just may be a placebo effect. Still have a vibration coming from the body of the car mainly from 60-70 mph. Seems to simmer down after that until I get up to maybe 85+.

I brought it up to Almost 90 on the turnpike and put the car in neutral with the rpm at idle to let it roll on its own to slow down and it did the same vibration from 70 down to 60 and the seems to just stop vibrating. This leads me to think it’s not drive train related and probably not the tires.

I’m getting stumped to what to look at now. It seems like the vibration comes from the rear but could it be coming from the front? What else could cause this? Could it be something loose on the suspension?
Could it be something I messed up on the rear hub when installing the arp wheel studs?(had to dis assemble the drum brakes)
I know I have everything suspension wise replace and with poly bushings. I know this will cause a harsher ride but is this a side effect from being able to feel every little thing?

 

Swapped wheels with a friend of his Supra today and had the same exact symptoms. I’m thinking maybe the axles or something with the rear hub… still not sure where to go next

 

I had the car jacked up from the rears and had a friend run the car. The right wheel seems to very slightly wobble. It doesn’t seem like the tire or the rim, but more like the aren’t spinning on plane. The body of the car vibrates when I get it up to the same speeds on the speedo as when I drive it. I feel like it’s something other than the wheel and tire it self as it has the same symptoms with my friends wheels on. It also had a noise coming from that side. Does this look like possibly a bad wheel bearing?

 

You definitely have a unique problem. If I understand you have:

• Checked driveshaft balance
• Changed diff
• Tried different wheels/tires

That doesn’t leave much, I am thinking one of three things; drive shaft u joint, Cv axle issue, wheel bearing. One other thought, I am not familiar with the one piece drive shaft so where are the u joints? What is done to replace the factory Guibo (rubber flex joint) at the diff?

U joints can be notchy and cause your issue in the factory drive shafts but with the one piece I assume the carrier bearing is not used as well as the flex disc. Cv axles usually are easy to diagnose if they have an issue, but I would check them closely. Wheel bearing you can usually hear when them above the drive train noise when you have an issue but again they can cause your symptoms. You should have slack or endplay if one of those is bad. Anyway keep us informed.

Edit: This is what a bad wheel bearing sounds like. You have to wait until a turn when there is not so much engine noise but the noise that sounds like a rub is the wheel bearing. Go to about hour 4 and later you can hear it. We ended up finishing this race with no bearing left and the caliper holding the wheel on. This is in a friends sc that he and I trade out driving in each others sc.

 

Turned out to be the 1 piece drift motion drive shaft, I’m assuming because of the solid aluminum adapters. I put a sc400 drive shaft and it’s smooth as butter. Hopefully it will last me for now I’ll think of other drive shaft options as I make more power

 

This is excellent news!!! That SC400 driveshaft will not let you down. It is very strong.

The solid aluminum adapters probably are part of what has been causing your vibrations. The factory driveshaft has rubber isolator donuts and a dampened center bearing for a good reason.

I hope this means you can go back to enjoying the drive with the GTE SC you have worked so hard to build!