Lexus IS Forum banner

1 - 20 of 47 Posts

·
Registered
Joined
·
189 Posts
Discussion Starter #1 (Edited)
UPDATE ON LAST PAGE:
Going to a 2-piece driveshaft solved the issue!




Original Post:

I am in need of help figuring out a crazy driveline vibration I am having after doing an AR5 transmission conversion.

It gets noticeable after about 40mph, and starts to violently shake the whole car after about 50. It gradually worsens as speed increases, and does not fade away after a certain speed.

Tires are not the issue. When the rear wheels are lifted off the ground and I run the car through the gears, the vibration heavily resonates through the whole car as if I had subwoofers in the trunk and was doing a frequency test.

The engine and the rear end were not touched, other than clutch and flywheel. Only the driveshaft and the transmission were changed. The transmission itself has about 80k miles, and shifts beautifully. I do not believe it to be the issue.

I am using a 1 piece driveshaft that bolts directly to the differential flange, and bolts to the transmission using the Driftmotion 6 to 4 bolt adapter. I had the outer diameter of the adaptor machined down by a driveshaft shop to eliminate any clearance issues with the JZX110 shifter housing.

I have checked every location where the driveshaft could possibly come close to contacting anything. I even removed the heat shield above the driveshaft. There is no contact anywhere, and the driveshaft has proper clearance throughout its length.

Its a brand new driveshaft, but the symptoms seemed that it could be out of balance. At the driveshaft shop, we removed and inspected the driveshaft thoroughly. There is zero play in the U-joints, and the driveshaft spun true and straight on the balancer. The driveshaft was re-balanced at a higher sensitivity, and balanced perfectly fine. Every nut and bolt was double checked and re torqued.

After putting everything back together, the issue is still present, and the car still violently shakes after 50mph.

Has anyone else ran into this issue? Other than lighting the car on fire, I am out of ideas on what to do next.

Any help greatly appreciated
 

·
Registered
Joined
·
576 Posts
I would say it's your driveshaft too, but you have double checked that.

The next course of action would be the driveline angle, so maybe the transmission is up too high. I don't know the angle that works with our cars, but I had the same kind of issue when I did rear heimed 4 links and traction brackets on a AE86 back in the day.

I would also look at your transmission and differential mounts to see if there's any cracks in the rubber or any extra movement when you shake them back and forth.
 

·
Registered
Joined
·
1,260 Posts
need a magnetic angle gauge, trans output and rear diff input need to be the same angle. my car i had to shim trans mount as high as i could get and had to drop front of rear diff. make sure trans yoke is tight also.


+ figs rear diff mounts are nice to add

if trans gets spaced to high and hits tunnel at all itll be a constant vibration but car can be started in air to double check that
 

·
Registered
Joined
·
5,270 Posts
I had to have my "Drive Shaft Shop" shaft re-balanced locally. Mine didn't vibrate till a higher speed but if you have an automatic diff, your DS will turn more RPM's than mine at the same speed.

The next course of action would be the driveline angle, so maybe the transmission is up too high. I
Typically people seem to install them too low. That's why you need the top-hat on the shifter spot. So the transmission can be high enough to get a good drive line angle.

I'd probably use a dial indicator on the output flange of the transmission and the adapter to measure run-out. I'd probably do the shaft on that end also. Just turn it over by hand and see how much run-out you have.

If I remember properly, the adapter from drift motion didn't seem to have a lip to center the install. Instead it depended on the bolts. The DSS adapter I got had a lip on the transmission and DS end to guarantee that they were centered.

Might be a good idea to check the output bushing on the transmission by moving the output shaft up and down to make sure it's not flopping.
 

·
Registered
Joined
·
189 Posts
Discussion Starter #5
Interesting. I will have to get a magnetic angle gauge and check the flanges. I would have guessed that the U Joints allow for some tolerance in a difference of transmission and driveshaft angle though, no?

I do already have the polyurethane Figs differential mounts, but the transmission mount is worth looking into.

I could not find any crossmember / mount system designed for the swap, so I did what others have done and used the stock transmission crossmember with the stock transmission mount.

The crossmember itself is attatched to the car usimg all 4 bolt holes, but I had to flip the actual transmission mount 180 degrees, and am only using 2 of the 4 bolt holes that connects the mount to the transmission, which had to be widened just a little.

I was a little skeptical at first, but have heard from multiple sources running the AR5 swap that this is the method they utilized, and had no issues with it.

For what it's worth, the transmission does appear to be in there pretty solid when tugging on it, and does not behave funny when hard shifting gears.
 

·
Registered
Joined
·
5,270 Posts
I could not find any crossmember / mount system designed for the swap, so I did what others have done and used the stock transmission crossmember with the stock transmission mount.
Not that I'm suggesting this is wrong but most of the AR-5 people I've seen didn't use the stock cross member. I used a MK2 supra one I modded and many people use the one for sale on Ebay. It's basically a bent piece of 3/16 or so steel.

https://www.ebay.com/itm/Custom-Ar5-To-IS300-Crossmember/153090658115?hash=item23a4ea0f43:g:1foAAOSwRqBbQSnU

 

·
Registered
Joined
·
189 Posts
Discussion Starter #7 (Edited)
I had to have my "Drive Shaft Shop" shaft re-balanced locally. Mine didn't vibrate till a higher speed but if you have an automatic diff, your DS will turn more RPM's than mine at the same speed.

The next course of action would be the driveline angle, so maybe the transmission is up too high. I
Typically people seem to install them too low. That's why you need the top-hat on the shifter spot. So the transmission can be high enough to get a good drive line angle.

I'd probably use a dial indicator on the output flange of the transmission and the adapter to measure run-out. I'd probably do the shaft on that end also. Just turn it over by hand and see how much run-out you have.

Might be a good idea to check the output bushing on the transmission by moving the output shaft up and down to make sure it's not flopping.
The differential is the standard 3.7 M85 that came with the car, but there were no issues found when re-balancing the driveshaft.

What top hat on the shifter are you referring to? The only thing I can see that would affect the angle is the transmission mount.

I'll see if i can source a dial indicator to check the trans for runout. The driveshaft may be tough, unless this will work while leaving it attatched to the trans? I am not familiar with using this tool

Regarding the output shaft on the trans, I can't grab the splined shaft itself, only the flange. It doesn't really seem to move, maybe a very small amount, but I believe that is considered normal?
 

·
Registered
Joined
·
189 Posts
Discussion Starter #8
I could not find any crossmember / mount system designed for the swap, so I did what others have done and used the stock transmission crossmember with the stock transmission mount.
Not that I'm suggesting this is wrong but most of the AR-5 people I've seen didn't use the stock cross member. I used a MK2 supra one I modded and many people use the one for sale on Ebay. It's basically a bent piece of 3/16 or so steel.

https://www.ebay.com/itm/Custom-Ar5-To-IS300-Crossmember/153090658115?hash=item23a4ea0f43:g:1foAAOSwRqBbQSnU

Thank you! For some reason when typing in IS300 AR5 crossmember on ebay, I was unable to find this. It's a little pricey, but worth it if it will fix my issues.

I do not have that rubber mount as shown in the picture, I am guessing I will also need to purchase the factory 06 Solstice transmission mount in addition to the custom crossmember?
 

·
Registered
Joined
·
754 Posts
i follow someone on IG who is having the same problem as you with the same trans. he wasnt sure if his output shaft was bent. i think he is still diagnoing it. PM me if you want his handle.
 

·
Registered
Joined
·
5,270 Posts
The differential is the standard 3.7 M85 that came with the car, but there were no issues found when re-balancing the driveshaft.
If you started as an automatic then stock was 3.93 I believe. The 3.70's were in the manual cars.

What top hat on the shifter are you referring to? The only thing I can see that would affect the angle is the transmission mount.


The sheet metal for the manual and automatic transmission tunnels are different. I'm not clear if you started with a manual or an automatic chassis. Automatic chassis, the transmission tunnel needs to be cut to permit the transmission to sit high enough. The manual car sheet metal for the tunnel has this hump for the shifter. This picture was my car which started out as automatic. I cut out the tunnel and mounted this "hat" to make it like a manual chassis.
 

·
Registered
Joined
·
189 Posts
Discussion Starter #11
If you started as an automatic then stock was 3.93 I believe. The 3.70's were in the manual cars.

The sheet metal for the manual and automatic transmission tunnels are different. I'm not clear if you started with a manual or an automatic chassis. Automatic chassis, the transmission tunnel needs to be cut to permit the transmission to sit high enough. The manual car sheet metal for the tunnel has this hump for the shifter. This picture was my car which started out as automatic. I cut out the tunnel and mounted this "hat" to make it like a manual chassis.
Ah okay. To clear things up, the car was an original W55 manual prior to the AR5 conversion, so no modification to the transmission tunnel was needed. There does not seem to be any contact with the transmission and the tunnel up there.

Another thing I should mention is that I changed my engine mounts, and my stock ones came out broken in two pieces. Its possible that the new mounts make the engine sit slightly higher up, and it appears that the custom crossmember allows the transmission to angle down slightly.

I am guesing my transmission is mounted too high since I am using the stock crossmember, and I can add some washers between the crossmember and the body of the car to correct the angle for the time being.

I am also guessing I will need to purchase the Solstice rubber transmission mount if I purchase the crossmember?
 

·
Registered
Joined
·
505 Posts
Can’t comment on your driveline vibration, except to say that sucks and I hope you get it sorted. My ar5 swap went without issue. I too replaced the stock motor mounts with some Megan’s because the original were broken in half. However I used Curran’s tranny mount. His build thread shows how he measures the driveline angles to arrive at how to properly bend his mount. You will need the rubber isolator from a solstice, think it was like 25$ or so. I figured his way was mathematically proven vs the upside down/flipped w55 x-member, so it was worth the 125$ custom mount. The violent vibration you’re describing sounds like there’s some slop somewhere in the driveline. Loose driveshaft-to-diff flange, or the tranny is bucking in its mount. I’ve been in a car where the ds had lost a couple bolts to the diff and the other two bolts were loose and it had a “clunk” when it made each elliptical rotation at slow speed and had a pretty good reverb at medium speed.
Good luck with it!
 

·
Registered
Joined
·
5,270 Posts
The violent vibration you’re describing sounds like there’s some slop somewhere in the driveline. Loose driveshaft-to-diff flange, or the tranny is bucking in its mount. I’ve been in a car where the ds had lost a couple bolts to the diff and the other two bolts were loose and it had a “clunk” when it made each elliptical rotation at slow speed and had a pretty good reverb at medium speed.
Good luck with it!
From a trouble-shooting perspective. All was good before the swap, then it went to shit after the swap. That suggests the problem is in the new parts and not the existing ones.

One thing I might consider in your shoes is to mod the stock two piece DS and use it instead of a one piece.
 

·
Registered
Joined
·
1,260 Posts
If you go with the curran mount be sure you have the bracket that bolts to the trans before the solstice rubber mount as its discontinued. Wouldve had to remove it to get the w55 mount on there
 

·
Registered
Joined
·
189 Posts
Discussion Starter #16 (Edited)
Update: I purchased and Installed the proper Curran crossmember, as well as a brand new mount.

I installed it yesterday, and noticed it seemed to change the height that the rear of the transmission sits it. I assumed this corrected the angle, or at least is a step in the right direction.

Unfortunately, I drove the car through the gears in the air, and the vibration still starts at 45mph and did not seem to change

My next step will be to remove the driveshaft and measure the angles, and start adding some washers to raise or lower it some more.



Regarding the above posts^

I have checked to make sure nothing is loose, and I agree that the problem is likely with the new parts, since it did not exist before.

If it comes down to it, I may actually consider getting that 2 piece driveshaft made, if that's what it takes to drive the car without the vibration.

Which figs bushings did you install?
Both of those are installed

If you go with the curran mount be sure you have the bracket that bolts to the trans before the solstice rubber mount as its discontinued. Wouldve had to remove it to get the w55 mount on there
I have that bracket, but theres some bad news. I did the original install with friends help. After taking off that bracket, the w55 mount was slightly too narrow to fit.

While I was working on something else, without me knowing, one of them shaved down the actual transmission housing in order for the mount to fit.

I was pissed when I saw that he shaved the actual transmission, instead of the mount, but now there is nothing that can be done.

With the w55 on, it sat snug and did not make the trans jump around when shifting. Now when trying to mount the original bracket, it does not sit snug against the transmission, as there is a decent gap where they should be touching. I will try get a picture when I am down under the car again.

When shifting gears in the air, it seemed like the transmission jumped up and down a good bit, and I'm guessing that's the reason.

I will likely have to shave the trans a little more and add a washer, possibly a rubber washer. Aside from replacing the whole tailshaft housing on the trans, I am not sure what else I can do
 

Attachments

·
Registered
Joined
·
1,260 Posts
thats how i did my trans mount didnt like the look of half the mount being used so made a bracket to cross top. Stock cross member slotted mounting holes a touch, aftermarket w55 mount




[/URL][/IMG]
 

·
Registered
Joined
·
189 Posts
Discussion Starter #18
thats how i did my trans mount didnt like the look of half the mount being used so made a bracket to cross top. Stock cross member slotted mounting holes a touch, aftermarket w55 mount




[/URL][/IMG]
Sounds interesting, can you upload a different picture? That one is saying its a broken image
 

·
Registered
Joined
·
393 Posts
Had this exact same issue. My issue wasn't abated until I purchased a CV driveshaft from DSS. The solstice used a CV driveshaft too. DSS basically said they had too much trouble with a fixed transmission and fixed diff that they no longer would produce the type of shaft you're struggling with. The CV is smooth as butter..

I must have put on and taken off my 1 piece double u-joint with sliding joint about 50 times and even purchased a driveline analyzer machine off ebay. Check out my thread on the issue..
 

·
Registered
Joined
·
189 Posts
Discussion Starter #20
Here is my transmission with the new crossmember



You can see the gap I am referring to, between the transmission housing itself, and the bracket for the trans mount.

They arent shaved perfectly flat, so i might try to shave them enough to fit some 3/8" washers in there. Hopefully this can bring that part of the tailhousing to its original shape.


Had this exact same issue. My issue wasn't abated until I purchased a CV driveshaft from DSS. The solstice used a CV driveshaft too. DSS basically said they had too much trouble with a fixed transmission and fixed diff that they no longer would produce the type of shaft you're struggling with. The CV is smooth as butter..

I must have put on and taken off my 1 piece double u-joint with sliding joint about 50 times and even purchased a driveline analyzer machine off ebay. Check out my thread on the issue..
Interesting. I wonder why this is only an issue with some people's IS300s, but other people with the AR5 conversion have never had the problem.

Good to know that's another option. Does your diveshaft use a carrier bearing? Or is it still a 1 piece driveshaft?
 

Attachments

1 - 20 of 47 Posts
Top