Ok, I found all the write up's on how to install it. I just need to get the part.

I found this part by Energy Suspension: ENS-9-9103G

here is a link to it from Summit Racing:

http://store.summitracing.com/defaul...=egnsearch.asp

Is this what you guys are using? It is 1 9/16" tall. I already tried the help sections at all the part stores and couldn't find anything. I'd feel better using an ES one anyway.

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91 FC Coupe - 00 LS1/4L60E
9.94 @ 134.7 1.41 60ft - N20
10.5x @ 129.x 1.4x 60ft - Motor
NHRA Legal to 10.00
California BAR Certified
http://s78.photobucket.com/albums/j1...iK/1991%20RX7/
2003 Suzuki SV650 - Does what the car won't do.. pulls the front up!

This is by NO means definitive, BTW:

But its just a nub thats meant to keep the diffy from rotating on the axis of the rear axle *pinion angle, hence the name* and you want one thats ideally going to be mounted on the nose of it (towards the engine) with just a LITTLE clearance between it and the floor (or whatever youre bracing it against) so that it wont rattle during daily driving, but it will keep everything as it should be if it does load up and rotate... I think!

So, uh, just get down there and measure it off and trim one down? lol.

Again, I COULD BE VERY WRONG! Dont take my advice and destroy your floorboard :P

I've never heard of an IRS that needed a pinion "snubber" or bump stop.
They are pretty much exclusively for cars with solid axles, where the entire housing moves up and down. Not so with an IRS. The whole point is that each wheel moves independently while the carrier remians fixed.
So you won't need anything to soften the collision of the carrier with the chassis since the carrier doesn't move.

I'm not sure I understand why it is that you want a pinion snubber in the first place.......

What is the problem that you are having? We can help with the diagnosis if you give us the symptoms.........................

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Why a V8?

It just feels right........

Target weight: 2800 with 1/2 tank fuel
Target power: 417/417 Flywheel HP/Tq

From what I've read it seems that the snubber is being used as a crutch to assist the crappy stock diff mount. The FC chassis has a ton of reinforcement just forward from the differential flange, where the subframe connects. Using a pinion snubber moves the load off that reinforcement, which is not the greatest idea, IMHO. I'm going to fab something up to assist the stock mount but keep the load on the subframe where it belongs. I don't like the idea of a solid front mount because then I would have to use solid mounts on the rear as well (unpleasant), plus I'm a cheap bastard.

-Jeff

I just want to go drag racing next week and avoid the wheelhop I have been getting. Right now I'm not doing any road racing or auto-x.. I mean it has a 4000 stall in it.

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91 FC Coupe - 00 LS1/4L60E
9.94 @ 134.7 1.41 60ft - N20
10.5x @ 129.x 1.4x 60ft - Motor
NHRA Legal to 10.00
California BAR Certified
http://s78.photobucket.com/albums/j1...iK/1991%20RX7/
2003 Suzuki SV650 - Does what the car won't do.. pulls the front up!

Some of us use a pinion snubber to take the strain off the front diff mount and avoid breaking it.

Andrew

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"you were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets."

It's from Auto Zone in the "Help" section. (That's the packaging that's RED..) Is do this on any swap I'm into at the time.

Here's a few pics....

(Yes, there's a typo. Should read "Mazda".)

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Revving an old thread in response to a question.

A pinion snubber is one of the best mods you can do in a v8 rx7, particularly for FCs that have a known weakness with the front diff mount. In terms of what they do and why, I believe there's some misinformation above. However, Ls1_Powered has the best pics of the install and I didn't have my camera on me when I installed mine so I choose this thread to bump up anyways. Let’s talk forces!

The differential in an IRS has two key forces coming into it.

1) Twist in roll from the driveshaft.
2) The reacting force of the tires on the ground which in turn create twist up the two axles in pitch.

In engineering, any rotating force is called a moment and is measured via the force multiplied by the distance at which the force is applied. Force times distance (ft-lbs anyone?). The bigger the moment arm (sometimes called lever arm) the bigger the moment that can be applied (or reacted). So why should you care?

The diff is compliantly mounted to isolate vibration, but this compliance means the diff can move somewhat as it reacts the two forces above. Motion of the diff can create wheel hop which creates a hammering force that helps you snap axles. You can also fail the FC's front mount by exceeding the sheer strength of the rubber. Everyone wants to better control the forces but there’s been some poor suggestions floating around on how to do so.

We’ll start with the driveshaft: For a t56 the ~400 ft-lbs coming off the crank get multiplied by the 2.66 ratio of first gear to make for a peak of 1064 ft-lbs going into the diff. Call it 1000 ft-lbs to use round numbers. The diff is restrained and must react this force by transmitting it both into the chassis and out the axles. The two big wings coming off the diff cover are designed to carry the moment from the driveshaft. They’re spread apart by give or take 2.5 ft so each one only sees a couple hundred pounds of force (it's multiplicative right?). Note, this is a moment we’re reacting so one wing wants to rise and the other to drop. If you’ve ever heard a slow speed hammering on the bottom on your car from the rear end you might be the diff wing down coming in and out of contact. I tried to solve that with a home brew solution here, but it wasn’t enough so I just ordered the Mazda comp rear diff mounts.

Now the reacting force of the friction of tires with road also creates a twisting moment. This moment is in pitch and is reacted by the cover wings (which both want to drop) and the front mount which wants to rise. Because the front mount is just rubber glued between two vertical plates the big torque number from a v8 tends to tear the rubber loose or in half over time.

BAD IDEA WARNING: If I had one axe to grind on this forum it’s the idea of welding the front diff mount solid. Sure you can prevent the nose of the diff from rising but what happened to the other forces? Remember that 1000 ft-lbs coming in from the driveshaft? The front is now locked solid in both pitch and in roll. Suddenly instead of the wings carrying the driveshaft moment the front diff mount is trying to carry the torque. It’s only about 4 inches from the axis of rotation (1000 ft-lb = 1/3 ft X reacting force) so suddenly it’s seeing 3000 lbs instead of the couple hundred the diff wings would see in order to react the same torque. The reality is that the mounting point on the subframe can’t take it and the metal flexes until the diff wings actually start to coming into play. Flex metal back and forth with sufficient force and it cracks. It’s the definition of failure via metal fatigue. DO NOT WELD YOUR FRONT DIFF MOUNT SOLID. GIVEN ENOUGH STRESS CYCLES IT WILL BREAK.

OK I'm done...

Sooooo, wasn’t this thread supposed to be about pinion snubbers?!? Well, a pinion snubber is just an assist to help control the tendency of the nose of the diff to rise. It’s basically a block of rubber that installs between the chassis and the diff and has the advantage that it helps react the vertical load in compression rather than in shear. Some folks have even used a big bolt as a snubber but I don’t recommend it as the floorboard will yield from the hammering over time. Again LS1-powered has great pics of where this thing goes. The dimple in his pics is probably a spot weld. I tried to take relative measurements and had to install my snubber twice because I didn’t trust the dimple. It really is in the prefect spot.

By the way if you don’t run a snubber the bottom of the car may end up being a snubber for you. I had a mark where the diff housing had moved ~5/8” vertically and touched the e-brake dual cable bracket. Just picture how far the front mount has to offset to have that happen and you’ll better understand the forces at work here.

By the way a Mazda comp front diff mount would also help control the motion of the front of the diff. However, even with a Mazda comp front mount you’ll still want to run a snubber because you’re still limited by the shear strength of the rubber and it’ll tear in half eventually. The normal mounts should work fine so there’s no reason to upgrade unless you’ve already failed a stock piece. That said, the Mazda comp front mount is cheaper than the OEM part so if you fail one you might as well go that way assuming you don't grab one used.

A final point where I differ with some folk above is that I believe the snubber should be touching the diff housing, no 1/8" clearance required. There's no reason not to and I want my snubber assisting sooner rather than later. This is especially true of the Mazda comp front mount where the spring rate is higher.

So where do you get one? I bought mine from Charlie (Bowtie7) who had a two pack so unfortunately I don’t have the part number. Sucks huh? All that build up and I can't follow through with the goods... Can anyone jump in and post up the part number? The stepped style bump stop I used was the perfect length and I know it’s different from those in the other snubber threads I read through in preparing this. I already browsed through summit and didn't see it. I’ll add the P/N to this write-up if we can figure that out. If not I'll take some pics and measure mine next time I have the rear end out (not long given I have mounts to install and an axle to replace).

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LS1 FC: breaking it in, working out the bugs...
Link to my swap (HEY NEWBIE I wrote this for you)

Great stuff! Thanks Joel!
Damon

its help #31052
if autozone doesnt have it, they can order it for you. baxter auto parts also sells it, if you have that in your area.
the enrgy one is entirely too short. it should be like 4" long or so.
and yah- all it does is help prevent the front of the diff from moving up under load. thats it! we would just use solid front mounts to achieve the same goal, but unfortunately, subframes are prone to breaking at v8 power levels.

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