510 Z20e engine position and vibration

[brodster]

If your going from the stock L series / 4spd to a Z series / 5spd, you need a different trans mount.

As for the pan, I wouldn't use the stock L series pan on there unless you go with a L series trans.

 

Put a jack under the trans and unbolt the X member. I bet it will move by itself.

 

I did just that last night to see what was going on.

 

Actually the first thing I did was lift the passenger side of the motor with another modified engine mount. It did fix the oil pan issue; however, I think it worsened one of the true culprits. I also went under the car with my handy Harbor Freight angle finder and started making measurments. It seems that the differential to driveshaft angle has a difference of 5.8 deg. The tranny and driveshaft have a difference of about 2 degrees. Unnacceptable. The engine and tranny both need to be lowered and flattened to get the pinion angle into a more acceptable range.

 

After that I unbolted the tranny crossmember to space it down somemore. During the process it definitely relaxed the rubber mounts on both sides. The driver side one is still a bit twisted due to the motor mount not being modified correctly, but it seems that the tranny crossmember is forcing the whole motor about 1/4"+ forward.

 

Currently the plan is to drill two new holes, 1/4" back from the originals, where the tranny isolator mounts to the tranny crossmember. This also means I have to cut down the back of the crossmember to allow the isolator to shift back. Not ideal, but it should work.

 

This brings up a couple of questions:

 

1. Jester you said I need a new tranny cross-member. I haven't measured, but I assumed that the Z dogleg and L dogleg are dimensionally identical except for the difference in bell-housing angle. If that is the case, shouldn't the old method of modifying the stock 510 crossmember for the L-dogleg work for the Z-dogleg?

 

2. Have other people had to do any other mods to their stock tranny cross-member besides slotting it and spacing it down? There always seem to be a range of different opinions on how to install the dogleg, from straight bolt-in to lots of shimming and hacking. It seems to position it correctly, with the stock cross member, the procedure is somewhere in the middle.

[Sealik]

1. Jester you said I need a new tranny cross-member. I haven't measured, but I assumed that the Z dogleg and L dogleg are dimensionally identical except for the difference in bell-housing angle. If that is the case, shouldn't the old method of modifying the stock 510 crossmember for the L-dogleg work for the Z-dogleg?

 

2. Have other people had to do any other mods to their stock tranny cross-member besides slotting it and spacing it down? There always seem to be a range of different opinions on how to install the dogleg, from straight bolt-in to lots of shimming and hacking. It seems to position it correctly, with the stock cross member, the procedure is somewhere in the middle.

 

https://docs.google....jQ4MjMzZWE0MjRh

 

http://community.rat...on/#entry708173

[brodster]

https://docs.google....jQ4MjMzZWE0MjRh

 

http://community.rat...on/#entry708173

 

Good info. I don't have time right away to make the mounts, but it shows me where everything needs to be. Thanks

[brodster]

So here's an update on the vibration issue, etc: I ended up putting back in the modified motor mount on the passenger side and I modified the stock transmission cross-member further. Thanks to Sealik's post, I did some rough calculations and figured to meet the specifications of the transmissions adapters discussed in the linked articles, I needed to shift back the transmission about 3/8". As a temporary measure, I hacked the back off the transmission crossmember where the isolator bolts in. I ground it flush, and drilled two new holes 3/8" back. (When I get a chance, I will re-enforce the back section with some weld work). I also spaced the transmission with 1 1/8" worth of washers. (Again when I get a chance, I will use something like box tubing to fill the space). If you don't want to read all that: I spun the crossmember 180 deg, spaced it down about 1" and shifted back the rubber isolator hole 3/8".

 

This definitely relieved a bunch of stress on the driver side mount. It is still a bit twisted, but I will fab something up later that is a better fit. The passenger side rubber motor isolator is now actually pulling back bit. That one will have to be modified a bit. Good news is that the oil pan has about 1/4" clearance from crossmember.

 

I need to do a better measure on pinion angle when I get a chance, but things look better as far as alignment.

 

Currently, the vibration still exists around 40 mph.

 

I also noticed something else. When I accelerate hard, climb hills, our compression brake down a hill, there is a squeaking sound sometimes. It only seems to occur under heavy driveline load. Given that the U-joints have never been replaced in 200000 miles, the driveline hasn't been worked in 6 years and there has been some harsh angles on it since the swap, I am guessing the u-joints should be replaced couldn't hurt.

 

Here is another key point (I failed to mention that before :rolleyes: [face palm]), the entire front suspension has been completely rebuilt. We now have coilovers on 280z struts, GC camber plates, all new bushings, etc. Tires are new, wheels are balanced, bearings are new. ALIGNMENT is rough at best. I did a quick toe-in measure in the garage, and eye-balled the camber. I haven't had a chance to get it dialed in yet.

 

So in about 1 to 2 months, I will get the motor mounts dialed in, replace U-joints and get the alignment done. At that point if the vibration still exists, further troubleshooting will be necessary.

 

So

[ggzilla]

I doubt if you need to replace the U-joints. When you checked them by hand if they were fine then, they still are. You can easily tell if they are going bad when you have the driveshaft out. They can last 500,000 miles, but sometimes less.

 

A 40mph vibration is more often due to the front end alignmnet (or lack of alignment), unless it only occurs only acceleration, but not under slight de-celeration.

[brodster]

I doubt if you need to replace the U-joints. When you checked them by hand if they were fine then, they still are. You can easily tell if they are going bad when you have the driveshaft out. They can last 500,000 miles, but sometimes less.

 

A 40mph vibration is more often due to the front end alignmnet (or lack of alignment), unless it only occurs only acceleration, but not under slight de-celeration.

 

So far it seems like it only vibrates during acceleration. Whether it is heavy acceleration or light acceleration, once the car gets to about 40mph, a vibration starts occurring. However, I usually don’t take the speed above that, so it is possible that the vibration is not acceleration related. Perhaps if I take the speed up higher and coast down it will still vibrate.

 

Also, it doesn’t feel like the vibrations are emanating from the drive train. The shifter doesn’t really vibrate, nor does the output shaft of the transmission (currently there is no shifter boot on the car). It feels like the entire car, including steering wheel is vibrating.

 

I will update this thread when I make the aforementioned adjustments/repairs.

[datzenmike]

Throw a spare on and swap it around all four corners... see if the vibration goes away.

 

Squeak could simply be the exhaust pipe moving against something under torque load.

[DatWifey]

We don't have any spares that fit with the brake swap :huh: And, we're having to leave it as-is for at least a month while we're in between places to live, so we're going to just have to address it at a later point, maybe slight tinkering here and there, but nothing major for a while :(