Installed Jim's unobtanium diff bushings and here is the story so far:

First, I used the directions that Jim wrote in a realted thread about how to remove the dif mount without having to take apart your entire car.

It wast to bad, not much space there but it worked out ok:

Pic of diff dropped down:


Basically you just remove the underpanels and catback for room, then support the diff with a jack, remove the bolts holding the diff mount to the car frame, drop the jack and the diff will drop (remove the cross bar that goes through the PPF!!!), the axels will hit rubber stoppers on the car frame and then you have enough room to get tools up on top of the diff (not easy though) and remove the 4 nuts that hold the brace on. It took a lot of 'persuading' for a lot of things, like getting the dif to drop enough, i had to pry it down, and i had to hammer (gently) the dif mount to get it to seperate from the diff/car frame, et, et.

Then I got the diff bushings pressed in:


Not a big deal, had a local auto shop do it since my press had not arrived yet and I need the car together for this weekend (road america track event).

Then I greeeessed up the pins and tapped them in, they are easier to go in from the inside rather than outside because the flange on the out side compreeses the hole just a tiny bit more, mine slid in part way from the inside, then i tapped them flush.



Then re-installed in reverse of teh removal, HOWEVER, it is very tricky to get it back in right and I had to do an extra step here, I first put the diff mount above the diff and pmounted it to the car frame points but did not tighten it down, then I raised the diff with the jack to get the studs to match up with the mount , took some prying and gettin-giggy-wit-it to get all the studs to pop in the mount, then I tightened the nuts on the mount studs hand tight, at this point he diff is pp high so you cant get tools in there, so I removed the bolts that hold the mount to the carframe and dropped the diff...again (hehhehe), then I had room to properly tighten the mount nuts on the studs and then jacked the diff up ...again (heheh)... this time the trick was lining up the care frame holes with the mount bushing pin holes, more prying and gettin-giggy-wit-it and finaly got the bolts in and torqed it all down...and ....

Boooya, unobtanium diff bushings now in the rear.

 

hey damian,

nice post as usual...

i am finishing my rear end project. new rear wheel bearings, pillowball bushings in the lower lateral link and a nylon bushing in the front of the latitudinal lower link and rear gears.

of course i used the opportunity to lose the rear rotor dust shields... anything for weight reduction.

since i had the axles out i decided to yank the rear gear assembly. all of a sudden no problems getting the diff mounting bracket off and on and properly torqued. as a bonus i had the opportunity to clean the diff and the underbody. it would have been a great time to swap fuel filters but i have about an hour on my filter...

i think going to nylon diff bushings is one of the better mods for the car. notice the slop in the bushings when you jack up the rear of the fd using the third member, there is at least an inch of slop! it is no wonder that you get wheel hop and blown rear gears w the rear bouncing up and down.

plus the car feels really good w the nylon bushings.

when will you be at elkhart? i am around until sunday when i leave for new jersey to pick up my Ito motor and would love to stop by. i'll bring my pyrometer...

howard coleman

 

Just what I needed to know, thanks Damian.

 

Damian,

once again, archivable write up! However I don't know if it was up to par with your other posts! Where is all of your multimedia and photoshopped inserts and diagrams!! Definitely of poorer quality when compared to your other posts!
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just kidding GREAT WRITE UP!

 

hey howard, good to hear from you. ill be in elkart lake this entire weekend (16th-18th), the event is with speedseekers (in conjunction with the f-body club) and I'll drive up friday and run on the track sat and sun. stop by if you can, I'll be up there with another 3rd gen guy and a bunch of other f-body car guys that I dont know (hehehe)

 

glad to help :-)

 

hahahah, i know i know, i was too lazy to do 3d rendering of the diff mount and animations of the bushing being pressed in (hahaha)

I actually had planned to take a series of pictures showing the exact steps visually, but my biz partner's wife had a baby recently so they got the camera for a while (hehehe)

 

did you tap a grease fitting? It took my about 6 hour by myself to do all to rear bushing.
-andrew

 

nope, I will do zerk fitting on the suspention once i get to installing those bushings, but the diff dosnt really move so I didnt zerk it, i just loaded the pins up with greese to help eliminate any sqeeking.

the suspention bushings actuallyt get rotaion during suspention movement, the dif dostn, it really just gets 'compression' forces on it, the pins dont 'rotate' in the bushing as the other suspention

if i had more time i would have zerked them just for fun :-) but I had to get the car back together for road america this weekend....so i ran out of time.

 

Another great write-up. It needs to become a sticky, or go into the archives in the suspension category. Thanks.

You need to do a write-up on a complete engine overhaul!!

 

thanks guys, I already PMed rxrotary2_7 and asked him about archiving it.

>>You need to do a write-up on a complete engine overhaul!!

hahaha, ... ahh yes, probably the only thing I have left to tackle on a 3rd gen rx7... an engine rebuild :-)

but lets hope I dont have to do that writeup for a looong time ;-)

 

The one tool that will make your life a 1000 times easier for this job are those "GearDrive" ratchet kits they sell at Sears. They're basically a low profile ratchet and with the space you have to work with, make a world of difference.

I used standard craftsman ratchets when I removed my differential mount bracket (Damian does kind of rush from diff still mounted to bracket off of diff stages ) and there was always something in the way - you will hate it, trust me. Unbolting the charcoal canister and temporarily removing it also helps provide more space.

Installed solid ones in mine:



Something odd I noticed but cannot really gauge (as I also replaced 6 rear pillow ***** at the same time) is that my ride height went *up* after doing the diff bushings and pillowballs.

Anyone else notice this? My car is rancho-spec now.

 

hey clayne,

>>(and Damian does kind of rush from diff still mounted to bracket off of diff stages ) and there was always something in the way - you will hate it, trust me.

yes, sooo true, it is a long and drawn out proccess of finding space to move tools/stuff in and out of there.

so those are diff bushings in the picture above? they look more like solid motor mounts.

 

That's because I pasted the wrong URL.



They're Kazama mounts.

In my case, I left the exhaust on. You don't have to take the muffler off, in fact, by leaving it on it tends to mute the "piece of ****" 's and "come the **** on already" 's eminating from under the car much better.

 

going to the archives... as alaways Damian, nice post.

 

Just did mine today, took me about an hour. Damian, instead of relowering it and all that jazz, I just tightened the top 4 bolts on the diff mount where it mounts to the top of the diff first. Then used the jack to push the diff up and it slid right in place. I believe that once you tighten the top 4, the mount *should* just slide right up into where the bushings mount to. At least thats what mine did. I was surprised at how easy this method was.

 

i also did mine recently and would like to point out a few things.

first you have to get the differential low enough. when u first start it the diff and wheels look like this ^ . but you want it to look like this V. i had to raise the wheels and place books underneat the wheels to get the diff low.


now to get the bolts off, was real easy if you look at the underneath of the car. you need a long bendable ratchet and a long thin bar. i used the removable jack handle for my bar.

place the the ratchet on the nuts holding the carrier to the differential. you can then adjust the ratchet so it is slightly bent, sticking out on the passenger side of the car. then use the rear sub frame to hold your bar in place and use it as leverage to push the ratchet. basically its a min pry bar. now you have to have one hand on the ratchet to keep it from sliding up or down against your 'pry bar'. all 4 bolts can be reached from this side, so no removing the charcoal canister or what not.

now when replacing the diff. dont use those little spacers that are on the OEM bushings. (per daminan, lol) they look like circles with crosses in the middle. just throw those away with the old busings.

bolt down the diff to the carrier. now if you have a problem getting the diff to line up, you can raise and lower the suspension knuckle right under the rear brake calipers. this will 'slightly' tilt the suspension and get it to line up. you may have to raise and lower the diff a few times, and raise and lower the wheels a bit also. after you get one bolt to slide in, raise and lower the other side wheel so it also lines up. you may have to remove the books now, dont forget. hooray, all done!

one note, these bushings add very noticeable whine at certain RPMs. its not bad, but it will be noticeable the first week. if you can deal with an AM exhaust and DP whistle, you might like the sound. overall feel is excellent. HUGE inprovement in launchs.
very very pleased.

 

good additions guys

 

Some things to add:

1. DO NOT try to drop the rear without a driveshaft and Torque Arm. The diff is almost impossible to get in and out as the bolts bind on the frame under the weight of the diff, and a jack is very difficult to get the perfect unloading. Took me 2 f-ing hours to get 2 bolts undone and out.

2. Unbolt the evap canister for a few extra inches to get the mount out.

3. Get the car as high in the air as possible. I did it with the wheels only 2" in the air, and that blew ***.

 

Great write up guys! I'm going to tackle this job next week..

 

I didn't have to remove my canister. I was easily able to access all 4 bolts from the exhaust side of the diff with my wrench. I also pulled the mount out from the exhaust side fairly easily.


Yes yes the higher the better.

 

Oh yea my impressions. I just installed the Jim lab diff bushings and I can easily say that this was the best mod I've done so far. I expected to hear lots of rear end noise but that wasn't the case. Under normal driving, everything is nice and quiet however, once you get on it you can hear a low rumble from the rear(almost like the exhaust opened up). I still have my stock cat-back so the little rumble sounds really cool. For those of you with aftermarket exhaust, you probably wont hear it at all. The car feels alot more solid and stable now.

Lastly, this mod by itself has damn near elliminated my wheel hop. Now don't go thinking that you can just install these and elliminate wheel hop. All the other rear bushings will need to be in good shape. My other stock bushings are still in perfect shape. My advice....Everyone needs to get a set of these you wont regret it.

 

hey guys
anyone know where i can get rear diff mount bushings?