[SOCAL.M6.ZLE]

Originally Posted by cdb95z28

Check alignment and obvious failed components. These cars are sensitive to alignment changes. Find a shop who will strive for perfection. As far as suspension arms, if you care about cornering and handling, don't swap arms with poly bushings. It's a downgrade vs the OE arms. The poly can bind and create an increase in wheel rate (suspension stiffness) which upsets the balance of the chassis. SPL and their superior spherical rod ends FTW if you really want to upgrade.

Similar experience here. A proper alignment helped alot, But that was after I ordered everything from the BMR catalog month 1 of owning the car, so the rear end has been locked down since day one. Not only do I remember that sloppy feeling in the rear end, I also remember the latency and disconnected feeling from the engine to the chassis... hard to explain, but the BMR motor mounts really helped with that also.

[ZLRob]

I've got that fishtail issue as well when I hit it hard. I have never checked the alignment and the I have not checked the shocks for seepage or anything the likes, but at some point I am definitely going to have to address it. Whether the issue be alignment or shocks issue or what have you. As SoCal mentioned the BMR motor mounts have really added a connected feeling back to the driving experience without a doubt.

[PowerDemon]

Do the BMR motor mounts improve shifting feel too? Any NVH in the cabin?

[ZLRob]

Originally Posted by PowerDemon

Do the BMR motor mounts improve shifting feel too? Any NVH in the cabin?

They do improve shift feel and I feel virtually no difference in the cabin but because we are muscle cars I like feeling the shakes in the cabin of the motor so regardless of whether or not it amplified the engine I don't mind it at all.

[PowerDemon]

Originally Posted by ZLRob

They do improve shift feel and I feel virtually no difference in the cabin but because we are muscle cars I like feeling the shakes in the cabin of the motor so regardless of whether or not it amplified the engine I don't mind it at all.

Actually I was hoping it increased NVH lol. Sometimes I think these cars are too soft for what they are.

[ZLRob]

Originally Posted by PowerDemon

Actually I was hoping it increased NVH lol. Sometimes I think these cars are too soft for what they are.

I agree. Lol. This was a nice change up to the OEM hydraulic motor mounts which always fail quick anyways.

[PowerDemon]

Originally Posted by ZLRob

I agree. Lol. This was a nice change up to the OEM hydraulic motor mounts which always fail quick anyways.

How involved is the process to install them yourself? Or did you have them professionally installed?

[radz28]

Originally Posted by ZLRob

I've got that fishtail issue as well when I hit it hard. I have never checked the alignment and the I have not checked the shocks for seepage or anything the likes, but at some point I am definitely going to have to address it. Whether the issue be alignment or shocks issue or what have you. As SoCal mentioned the BMR motor mounts have really added a connected feeling back to the driving experience without a doubt.

This will, probably, sound obvious to most, but didn't occur to me, so I only want to add this because it might be relevant.

I've found that TOURING MODE might cause some of this (and there are previous posts from others that seem to support this). If you're in TOURING, you might try a different mode, too, and see if it's still there. I spent money on the whole catalog of rod-end arms for the rear, including ZLE bushings and wheel alignment. Even on new DRs, the problem was still there. I could induce a dart'iness at low speed, too, by dragging on the brakes (hard) and putting a high-load on the engine (I was tuning), and in TOURING, the car would dart all over the place, even at speeds less than 50-MPH. The car would push right-and-left (nearly uncontrollably) even though the tires weren't spinning. I had a kungfu grip on the steering wheel, but it was enough to dart back-and-forth into adjacent lanes. As soon as I changed into SPORT or TRACK, the darting, seemed, to all but disappear. It was VERY strange, and was unnerving. It was worse the faster I went, even if I wasn't dragging on the brakes. I'm surprised I didn't crash many times when this would happen (great chassis engineering probably helped, lol), but high-speed was VERY disconcerting. In SPORT or TRACK, though, not a big deal.

I'll admit that, probably, no one would put their car into that kind of configuration, but I wonder if it was the ELSD that was the culprit. I don't know that for sure, but I just wanted to drop that here, in case it needed to be said again.

[ZLRob]

Originally Posted by PowerDemon

How involved is the process to install them yourself? Or did you have them professionally installed?

It was not hard at all but I had the engine out doing the build on it at the time so everything was insanely accessible for obvious reasons. If you're doing it on the vehicle you would just need to remove the shielding at the bottom, use a jack with a block of wood on it to support the oil pan and do one side at a time. The supports for the mounts themselves are very cumbersome and overly large so that may restrict some access to the bolts needed to remove them from the block.

Originally Posted by radz28

This will, probably, sound obvious to most, but didn't occur to me, so I only want to add this because it might be relevant.

I've found that TOURING MODE might cause some of this (and there are previous posts from others that seem to support this). If you're in TOURING, you might try a different mode, too, and see if it's still there. I spent money on the whole catalog of rod-end arms for the rear, including ZLE bushings and wheel alignment. Even on new DRs, the problem was still there. I could induce a dart'iness at low speed, too, by dragging on the brakes (hard) and putting a high-load on the engine (I was tuning), and in TOURING, the car would dart all over the place, even at speeds less than 50-MPH. The car would push right-and-left (nearly uncontrollably) even though the tires weren't spinning. I had a kungfu grip on the steering wheel, but it was enough to dart back-and-forth into adjacent lanes. As soon as I changed into SPORT or TRACK, the darting, seemed, to all but disappear. It was VERY strange, and was unnerving. It was worse the faster I went, even if I wasn't dragging on the brakes. I'm surprised I didn't crash many times when this would happen (great chassis engineering probably helped, lol), but high-speed was VERY disconcerting. In SPORT or TRACK, though, not a big deal.

I'll admit that, probably, no one would put their car into that kind of configuration, but I wonder if it was the ELSD that was the culprit. I don't know that for sure, but I just wanted to drop that here, in case it needed to be said again.

I actually experience the issue regardless of what mode it's in. Now that you mention it though I do wonder if it is an eLSD interference issue. Like it's trying to overcompensate for what you are trying to do. I also wonder if it's a mode based thing that if the Driver Demand tables may have an influencing factor in it.

[ICE_MODE]

I posted this elsewhere, but check your toe link bushings. Both of mine (SS1LE so the sphericals) were worn out at 40k miles. Lower trim cars have rubber bushing toe links.

I could jack up a rear tire, and get it to clink-clink in the toe axis with a little bit of force. Both sides. Result is car would feel like the back end was following invisible ruts in the road, which was felt mostly as a head wiggle by the driver. Got worse over time.

85550692 is the current part number, supersedes 23117751. ~$85/ea online.

If you want the ultimate in OEM bling, you can get the Cadillac CT5-V Blackwing Precision Package ones for $1000/ea, p/n 85016345

Checking this takes a touch of effort and but at least it's free. Alignment check might not find it as the problem is passively variable alignment.

[WhiteMale]

I just put BMR toe rods on my car last night, headed to the alignment shop now. Wanted to say that when I had the stock toe arms on my bench those rubber bushings were ungodly level of soft with 23K miles on them.

Ive got most all the other BMR goodies back there...rear sway bar, cradle lockout, front braces, upper control arm, and both trailing arms.

[cdb95z28]

Originally Posted by WhiteMale

I just put BMR toe rods on my car last night, headed to the alignment shop now. Wanted to say that when I had the stock toe arms on my bench those rubber bushings were ungodly level of soft with 23K miles on them.

Ive got most all the other BMR goodies back there...rear sway bar, cradle lockout, front braces, upper control arm, and both trailing arms.

Are you talking about the arm pointed out in the pic below? That is the toe rod.

The OE toe rod "bushings" on all ZL1s and SS 1LEs are actually spherical balls. It wasn't soft, it is bind free precision movement. Just like aftermarket rod ends, but no noise and sealed. These joints are excellent joints. The biggest reason most guys change them out is because the 12mm eccentric adjuster torque to yield bolt is undersized and per GM one time use only. And it doesn't tend to hold an alignment under certain loads. The arm structure itself is very good, at least for the handling crowd. I had the SPL toe rod and eccentric lockout on mine but went back to the OE arm with a larger 14mm eccentric bolt that I made. I can understand the drag racer guys wanting to stiffen them up, but going to poly is a step backwards IMO. Stay with rod ends. Poly on any of the joints is not good, it will bind when loaded and eventually deform. And they periodically need lubed. Only place worthy of poly is on aftermarket anti roll bar mounts. But even BMR's own mounts suck.

[radz28]

Originally Posted by ZLRob

It was not hard at all but I had the engine out doing the build on it at the time so everything was insanely accessible for obvious reasons. If you're doing it on the vehicle you would just need to remove the shielding at the bottom, use a jack with a block of wood on it to support the oil pan and do one side at a time. The supports for the mounts themselves are very cumbersome and overly large so that may restrict some access to the bolts needed to remove them from the block.

I actually experience the issue regardless of what mode it's in. Now that you mention it though I do wonder if it is an eLSD interference issue. Like it's trying to overcompensate for what you are trying to do. I also wonder if it's a mode based thing that if the Driver Demand tables may have an influencing factor in it.

That might, also, explain a little inconsistency. I get varying levels of how bad it does this - sometimes it's pretty bad, and other times it's there, but doesn't seem as bad as before.

I will admit that my DD tables are slightly modified, but that's higher in throttle mapping - not around the middle to lower parts. I, basically, kept the OEM mapping (on all three modes) OEM except for WOT, and blended into the 70/80% range. My VTT and VVE models are also a little massaged, so that might be other possibilities.

Originally Posted by cdb95z28

Are you talking about the arm pointed out in the pic below? That is the toe rod.

The OE toe rod "bushings" on all ZL1s and SS 1LEs are actually spherical balls. It wasn't soft, it is bind free precision movement. Just like aftermarket rod ends, but no noise and sealed. These joints are excellent joints. The biggest reason most guys change them out is because the 12mm eccentric adjuster torque to yield bolt is undersized and per GM one time use only. And it doesn't tend to hold an alignment under certain loads. The arm structure itself is very good, at least for the handling crowd. I had the SPL toe rod and eccentric lockout on mine but went back to the OE arm with a larger 14mm eccentric bolt that I made. I can understand the drag racer guys wanting to stiffen them up, but going to poly is a step backwards IMO. Stay with rod ends. Poly on any of the joints is not good, it will bind when loaded and eventually deform. And they periodically need lubed. Only place worthy of poly is on aftermarket anti roll bar mounts. But even BMR's own mounts suck.

Attachment 1162181

I can confirm that my car had rod ends for that bar, too.

[DeuceCam]

The issue is present on non eLSD cars. I have an LT1 with bmr subframe lockout and SPL toe links. Still happens. I'm guessing it's either the alignment and/or tires. Could also be slop from other rubber rear arm bushings, or possibly inherent to the chassis.

Edit: Could also be related to TCS/ESC/stabiltrack etc.