When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Took us 9 hours...three of which were just getting the rear diff bushing out. I used the Z1 removal tool and the rubber part of the bushing came out pretty easily, but the steel sleeve took a long time and many, many wrench strokes in the tight space. Got it out finally, though. Replaced all three stock bushings with Z1 solid urethane bushings. I did not need to remove any of the stock exhaust or loosen the anti-sway bar to do the removal or installation; it was tight but with two people holding it and maneuvering it we managed.
I'm still in the break in phase so no stomping on it yet. But after 60 miles so far (in 2 separate trips with cool down in between) I can say cruise control still works! That is, at up to 60 mph, which is as fast as I've gone so far.
One BIG difference I've noticed is from the bushings - I love them! Since the Transgo kit installation I've noticed that sometimes shifts (especially 2-3 and 3-2) are accompanied with a thud from the rear...NOT ANYMORE. All shifts so far have felt very smooth and solid, the drivetrain feels much tighter and slop-free. I like it.
There is a very low gear whine on and off at 55-60 mph when the car is coasting, which I attribute mostly to the solid urethane bushings. Perhaps break in will reduce this, but it's not at all loud. I hear it because I'm listening for it.
That's it so far. I've attached pics of the Z underside with the diff out and also after rear bushing removal.
Update: after 130 break-in miles, 20 or so at a time with cool-down in between, the little bit of gear whine around 50 mph is greatly diminished. It sounds maybe 5-10% louder than the stock 3.3 gears. At all other speeds below 50 it's just like stock. Completely acceptable. Whether it's the gears, the bushings or some combination of the two breaking in, who knows.
Now that I'm past 100 miles I can take it up to 65 to 70 mph. At 500 miles I'll change the gear oil and then it's fun time! Cruise control still working.
71MPH is right at 3000 RPM. The drain plug was cleaned, so whatever is on there was from my gears. At about 280 miles now. Should be at 500 by the end of the week, then I'll change my gear oil and see what's on the plug.
Hmm...seems like I made a mistake in the installation of the new bushings. There is a black metal "tophat" washer on top of the stock front bushings that isn't mentioned in the directions. I put it back on top of the new bushings. I asked Z1 about it and Russ just told me that it should be left out, so I guess I'll pop those out when I change the diff fluid at 500 miles. Hopefully I can just pull one bolt at a time, tilt the diff a little and slide them out. Not a huge disaster.
Hmm...seems like I made a mistake in the installation of the new bushings. There is a black metal "tophat" washer on top of the stock front bushings (about 1/4" thick) that isn't mentioned in the directions. I put it back on top of the new bushings. I asked Z1 about it and Russ just told me that it should be left out, so I guess I'll pop those out when I change the diff fluid at 500 miles. Hopefully I can just pull one bolt at a time, tilt the diff a little and slide them out. Not a huge disaster.
Hey, I had a 50:50 chance with my guess...
If you don't have vibration from the driveline it's probably not an issue but try it and see if it changes anything.
I do notice a little bit of vibration some times, not a huge amount but sometimes I get a low chugging when I'm accelerating, although it is not consistent. Sounds kind of like the engine but out of sync with it. Hoping that removing the plate will eliminate that. Doing it today after work.
That was easy enough. About a 10 minute job to loosen the three diff bolts, remove the front bolts one at a time, and slide the black washers out. No problem. The intermittent minor vibrations are gone, not that they were very noticeable anyway.
Still some increased gear noise at certain speeds (45 and 65 mph, other speeds quiet as stock), but I guess that's the price for having solid poly mounts. I think I'll dynamat the trunk and then it should be pretty quiet..
Changed the gear oil today at about 575 miles. Break-in was done with Pennzoil 80W90 dino oil. Just changed it to Redline 75W90 synthetic. I must say, the Redline significantly reduced the gear noise! I'd say the rear is now just as quiet as stock except for a very slight whine around 45mph - I'm sure a little Dynamat in the trunk will take care of that. At highway speeds of 70-75mph there is no gear noise at all.
Cruise control still works fine, tested up to 75mph.
The drain plug magnet had a coating of fine black particles on it, likely the worn material from the gear teeth breaking in. No big pieces or chunks (see picture).
Performance-wise I love the 3.7 gears. Acceleration feels significantly quicker than stock, and with the poly bushings and Transgo kit the shifts are fast and firm to keep me pushed back in my seat. These three mods go very well together.
Glad to hear you are enjoying your new gears. How is it when you stomp on it from 0mph? DO you get a lot of wheel spin?
My 3.9 rear diff project is put on hold until i can figure out why my oil pressure is low at idle. Cant seem to come up with an answer. Already changed the sensor and dropped pan. Engine sounds fine no ticking. Either pump decided to just randomly give up, or motor is toast after sitting for majority of last 2 yrs.
Fu$king hate idea of spending all the money to get the parts for upgrade and motor is toast.
09-03-2017, 04:11 AM
