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Eliminating the rubber bushings on the IFS compression rods


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I just finished modifying my Pathy to completely eliminate the squishy rubber crap on the compression rods (rear pivot of the LCA). I did this by replacing them with a spherical bearing in a machined steel housing welded to the frame. My goal is to eliminate all the rubber bushings in the IFS so the front wheels will point the same direction under high torque loads off road. After installing my Nismo front LSD and Swampers I discovered that with real traction up front the toe can change by a ton when climbing rock ledges and such. The biggest culprit is the rubber donuts at the back of the LCAs. My compression rod bushings and their retainer deals on the frame were in pretty good shape until I put the front LSD in. Five miles of trail and three of the retainer deals had sheared off the frame and the compression rods were trying to beat their way out of the hole in the frame mount!

 

I thought of doing this mod several years ago but the junk I had worked fine and why fix it if it ain't broke?! When I worked at Joes Racing Products I did a bunch of design work for the Alta/Perrin Group. One of the things I designed for them was their PSRS assemblies that replace a giant rubber bushing at the back of a LCA with a spherical bearing or similar. They do it to eliminate bushing deflection and improve the handling while also re-locating the pivot point to add caster. I didn't want to change the geometry, I was after eliminating all deflection. So I drew up an assembly in CAD and this is a cross-sectional view of it:

 

CompressionRodBearingAssemblyCAD.jpg

 

Red: Center line

Blue: Pathy frame (steel)

Green: Bearing housing (steel)

Cyan: Spherical bearing (all steel)

Grey: Spiralock bearing retainer (steel)

Yellow: Adapter bushings (303 stainless steel)

Purple: Lip seals (steel washer with rubber lip)

 

The spherical bearings I used are 1" bore, greasable, and rated for 82,800 pounds of radial load. I used these large bearings as they have more than three times the surface area that a bearing the stock compression rod will slip through does so they will last much longer. Also, I won't have to re-do this assembly when I fabricate heavy duty, high-clearance LCAs at some point down the road. I'll be able to shove a 1" grade 8 bolt through the bearing and into a boss on my fabricated LCA. I like bomb proof. :aok:

 

Here's the first housing on the lathe:

 

2012-07-07_20-49-20_583.jpg

 

This is the hammered dogschplit that was on the truck:

 

2012-07-10_21-44-20_261.jpg

 

I ground the face of the mount flat as there was rolled up material around the hammered-out hole:

 

2012-07-10_22-01-22_435.jpg

 

Made a template and marked the mount to open it up for clearance:

 

2012-07-10_22-03-12_927.jpg

 

Five minutes with a die grinder:

 

2012-07-10_22-24-37_156.jpg

 

And I had a 1-3/4" hole through the mount:

 

2012-07-10_22-25-09_515.jpg

 

There's no easy way to go back now so this better freaking work! LOL

 

There were some remains of the spot welds inside the back of the mount so I cleaned it up with my little pneumatic belt sander:

 

2012-07-10_22-28-42_975.jpg

 

A lip seal runs on this surface so it had to be relatively smooth, at least smooth enough to not tear or shred the seal.

 

Next up I through-bolted the housing with bearing installed to hold it securely in place for welding. When I made the housings I milled flats on two sides that act as indexing surfaces. When they're in the correct spot the bottom and inner edge line up with the edges of the factory mount on the frame:

 

2012-07-10_22-55-58_945.jpg

 

I'm posting pics of the 2nd housing as I actually did the passenger's side first. I learned a few things on that side. :headwall: The most important being that it's nearly impossible to press, pull, or pound the bearing into the housing after it's welded on without removing the LCA as there just isn't enough room to work. Removing the LCA is a major PITA so I decided to flush all the lube out of the bearing with carb cleaner, press it in, install the spiralock, and weld it with the bearing in place. Since all these parts are steel welding heat will not hurt them as long as they are allowed to air cool.

 

I TIG welded these on because... well... because I can! :sly: The weather has been hot and I was not in the mood to put on full leather gear and a Carbon-X balaclava (I have MUCH hair) under my welding helmet to protect against MIG splatter when welding overhead lying on a creeper. This was the first time I've tried TIG welding without a foot pedal. My torch has an amperage wheel and on/off arc button but I'd never used it. I'd say I did rather well:

 

2012-07-10_23-53-52_640.jpg

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A little baked on paint since the housing was 400F when I sprayed it (love that trick, paint dries in two minutes and is almost as tough as powder coat!) Screwed the Zerk fitting in, and it's ready to bolt in the compression rod:

 

2012-07-11_00-15-00_171.jpg

 

I guess I neglected to take a pic of the adapter bushings and stuff before I installed them. :(

 

Here's a bottom view of the completed assembly. Note that I also welded the two pieces of sheet that Nissan sandwitched together to make the frame mount. This side had been over some rocks really hard and was a bit tweaked at the bottom too:

 

2012-07-11_01-13-18_360.jpg

 

A bottom view from the rear, so you can see the rear lip seal and the spacer required because the threads don't go far enough on the stock compression rod:

 

2012-07-11_01-12-53_69.jpg

 

The large flat washer only retains the lip seal.

 

Looks like I didn't shoot a top-view pic of the driver's side so here's one of the passenger's side:

 

2012-07-10_17-28-33_702.jpg

 

You can see the lip seal runs on the face of the bearing housing. A stock Pathy compression rod washer retains the seal onto the adapter bushing inside and will also help to protect it from rocks and such thrown up by the front tire.

 

The truck handles and steers 700% better than it did prior to this mod... but the crap I was running was just about as destroyed as it can get and still drive. The driver's side compression rod was worn more than halfway through from rubbing on the frame! I used the rods from my parts truck as they were nice and minty. Now that this is done I really need TO GO WHEELING!

:lol:

 

If this modification proves to work as well as it should and be as durable as I think it will be I will offer a kit so others can do this. If this does go into production rather than using adapter bushings and stock compression rods I may include heavy duty, heat treated 4140 compression rods. They would be easier to install, several times stronger than stock, and my thinking is that most people that do this mod are going to need new compression rods anyway.

 

Oh yeah, if the mods think this should be in a different section please move it.

Edited by Mr.510
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Yeah I was asking him about this earlier. Seems to work really well but needs more testing. I'm debating if I should get a bearing race cup thing now or wait out for this. I'm leaning toward this method first unless he finds something wrong with it during testing. Other than that it looks like a fine product. :aok:

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This is sweet. When I first heard the bearing race cup mod, I was thinking to myself, What if you could replace the rubber bushings with a full bearing. If this is tested and in production before I get a chance to put mine back together, you might have one more buyer to add to your list.

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This sounds like a serious solution. Sure would be great to have something out there that effectively deals with a known issue. If its too hash with impact forces, what about a small skinny style isolator behind the front washer to possibly soak up a little of the force? If that would even work.... I don't know.. Just throwing it out there although I'm sure you've already thought of everything acceptable since you have WAY more knowledge then this dude. I'd be interested myself since I think my machined cups are burly, and probably provide less front end movement then what was there from stock.

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You might be onto something here. Maybe something like a rubber plug sandwiched in there? Also would be nice for the assembly to not required having to be welded in.

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Nice mod! I need to start with just taking mine apart to see how bad they are. I'm afraid I'll get it apart and it'll just all turn into a rusted pile of dust.

 

Thanks man. I would not take yours apart until you're ready to deal with fixing it. You don't really want to know what lurks in there! :lol:

 

The only thing that I am concerned about is how will these absorb full frontal impact on the frame. I guess I will see what happens in testing.

 

The bearing is going to transfer all rearward force directly into the frame. The factory frame mount is a pretty beefy part, fully boxed and welded into both sides of the frame rail. I cannot see damaging that with impact loads carried through that flimsy sheetmetal LCA!

 

This sounds like a serious solution. Sure would be great to have something out there that effectively deals with a known issue. If its too hash with impact forces, what about a small skinny style isolator behind the front washer to possibly soak up a little of the force? If that would even work.... I don't know.. Just throwing it out there although I'm sure you've already thought of everything acceptable since you have WAY more knowledge then this dude. I'd be interested myself since I think my machined cups are burly, and probably provide less front end movement then what was there from stock.

 

Hopefully the bearing proves to be durable in this application, that and NVH are the only things I don't have answers too. There's really no way to add a bumper or something to this, as that would involve parts sliding together that would wear out rapidly, especially when run in mud. The one upside that I didn't mention above is that there is almost zero friction in this arrangement so the suspension will move more freely. You can literally pivot the compression rod any direction and rotate it with your little finger when it's not bolted to the LCA. There isn't enough friction to even hold up the end of the compression rod.

 

Also would be nice for the assembly to not required having to be welded in.

 

It would be nice but there is no way to do it. I looked at it from every angle I could think of and there's just no way. I thought about doing something like the T/C Kits I produce for cars with a ball and socket but we have to deal with fore-aft forces since our trucks drive the front wheels. In RWD only applications the tension compression rods are only loaded rearward while driving so it's a non-issue. A 'one-way' solution with the stock rubber bushing behind the chassis mount just holding tension on it works great. I've produced somewhere waaaaay past 1000 of these T/C Kits.

 

Here's an "exploded view" of one of my T/C Kit pivots:

 

TCKitPivotAssy.jpg

 

Please ignore the white thread, I learned this trick from George Lucas! :lol:

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Please ignore the white thread, I learned this trick from George Lucas! :lol:

:lol:

 

beautiful lookign product though man, let us know how it holds together under your abuse!

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The one upside that I didn't mention above is that there is almost zero friction in this arrangement so the suspension will move more freely. You can literally pivot the compression rod any direction and rotate it with your little finger when it's not bolted to the LCA. There isn't enough friction to even hold up the end of the compression rod.

 

 

Next will be to put a bearing in place of the FWD LCA bushing. Those ones are REALLY spongy when the t-bars are off.

 

 

Please ignore the white thread, I learned this trick from George Lucas! :lol:

if you focus your energy and wave your hand like a Jedi while saying "there is no white thread" ...

Edited by MY1PATH
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Loving this one mr. 510... seriously. this is how it should have been from the factory. I highly doubt there would be any negative effects, seems like the truck should ride smoother and more controlled if anything...

 

I have poly in mine and I noticed a HUGE difference over stock (i also had one compression rod that was worn half way through before i went poly), this would seem like it would be another step above again and to me (in my brain, lol) seems it would help front end articulation...

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If you notice on the WD22 Xterra, they completely eliminated the tension rod. I don't have the slightest idea why Nissan even put these things there in the first place.

Edited by Tungsten
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Next will be to put a bearing in place of the FWD LCA bushing. Those ones are REALLY spongy when the t-bars are off.

 

I think because of how the LCA pivot works that one will have to be Delrin bushings, but I'm not sure yet. I haven't had that portion of a Pathy apart in a couple of years and I wasn't thinking in terms of eliminating all the rubber crap when I was in there. I'm getting ready to scrap my parts Pathy but I'm going to keep the front frame clip as it'll be handy for test-fitting and mocking up LCAs, my planned spindle mods, and stuff like that.

 

if you focus your energy and wave your hand like a Jedi while saying "there is no white thread" ...

 

starwars023.gif

 

 

Loving this one mr. 510... seriously. this is how it should have been from the factory. I highly doubt there would be any negative effects, seems like the truck should ride smoother and more controlled if anything...

 

I have poly in mine and I noticed a HUGE difference over stock (i also had one compression rod that was worn half way through before i went poly), this would seem like it would be another step above again and to me (in my brain, lol) seems it would help front end articulation...

 

Stuff like this was rubber mounted stock primarily to reduce NVH. (Noise, Vibration, and Harshness for anyone reading this that doesn't know.) Also, the stock rubber was likely much more durable than any bearing will ever be. My truck had 375k miles on it's original rubber bushings before they even looked bad. I will guess the maximum these spherical bearings could last is 100k miles. With the previously noted improvements I think $50 and a couple hours to replace the bearings every however often isn't going to be that big of a deal.

 

This being a spherical bearing will definitely help front articulation and compliance of the front suspension. It moves more freely and that is always a good thing. Whether it will be enough to feel or measure I don't know.

 

If you notice on the WD22 Xterra, they completely eliminated the tension rod. I don't have the slightest idea why Nissan even put these things there in the first place.

 

Virtually all of Nissan's independent front suspensions used "tension compression rods" (aka strut rods) and separate lower control arms. The two parts form a triangle to locate the lower ball joint and triangles are not easily bent or flexed. This is a very simple, cheap and easy to produce lower control arm setup that is quite strong and light weight. (Remember that unsprung weight *severely* effects vehicle ride and is the number one downside to a solid front axle.) The vast majority of T/C rods go from approximately the lower ball joint forward to the chassis as this makes the most sense, having the skinny rod loaded primarily so impact forces generated at the tire are trying to stretch it rather than push on it. The first IFS 4x4s Nissan sold here where the 720 trucks. They had long T/C rods going forward the way all the passenger cars (except early Zs) do. 720s also had torsion bars that plug into the LCA pivots so having the T/C rods go forward made all the sense in the world... until you ventured off road where they were very easily bent. Also, their mounting point on the bottom of the frame severely reduced approach angle. I wheeled an '81 720 on 32s for a few years and carried two spare sets of T/C rods and both bent and broke them on a regular basis. This was never from the tires hitting stuff, it was from running the rods themselves into stuff.

 

My guess is that when they designed the WD21 chassis the engineers had "tension compression rod on the brain" and didn't think outside that box. it was a proven design that worked well in everything else so it made a whole lot of sense to use it. If these trucks had all been thrown away at 150k miles very few people would have any complaints at all about the compression rod pivot bushings. Just like with the stock automatic transmissions: Nissan didn't make crappy parts, they built a truck that lasts too damned long! :aok:

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The bearing is going to transfer all rearward force directly into the frame. The factory frame mount is a pretty beefy part, fully boxed and welded into both sides of the frame rail. I cannot see damaging that with impact loads carried through That flimsy sheetmetal LCA!

 

Found some rock on the trail

 

b1dcf263.jpg

 

436e22f2.jpg

 

Granted that's a different load case but they can be bent...and would highly doubt the rod load would do this to that brkt

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  • 2 weeks later...

Found some rock on the trail

 

436e22f2.jpg

 

Granted that's a different load case but they can be bent...and would highly doubt the rod load would do this to that brkt

 

Damn, you must have hit that HARD! That's more than twice as bad as my driver's side was before I took the sledge hammer to it prior to welding the bearing housing on. I don't think there's any way the stock LCA/compression rod could bend that bracket unless the vehicle was in a major accident. I've seen lots of trucks in wrecking yards that were in head-on collisions where the frame is bent, the body is buckled, and the suspension is totally destroyed... but that mount is usually still intact and straight, at least to the naked eye.

 

This looks awesome!! Do you take orders so I could also do this to my Terrano??smile.png

 

Right now the only set of parts that exist are the prototypes that I'm testing on my Pathy. I need to run them for a while and abuse the truck more than usual to make sure the parts are going to live. Once I feel confident in the longevity of the bearing I will put these into production and offer them for sale. I'm going to say worst-case that would be around the end of the year. It's just a matter of me getting enough off-road miles on the truck. That takes a whole lot of money and time... but sacrifices must be made! :lol:

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I can see his point on testing out the bearings before selling them. He really doesn't want any damage to his reputation from people complaining about wrecked tension rods. It's not like you can go back to the factory set-up after you have gone this route. It's a one way street and there is no going back once you expanded out the hole.

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That's fair enough, from what I've seen on this thread I would buy them right now smile.png

 

Thanks, I appreciate the vote of confidence. I *think* they are going to work great and last a long time.

 

I can see his point on testing out the bearings before selling them. He really doesn't want any damage to his reputation from people complaining about wrecked tension rods.

 

Exactly, sort of. :lol: I'm actually more concerned about selling what turns out to be junk than hurting my reputation. As far as I'm aware nobody has done this to a wheeler before so this is new territory. I know it works and lives on high powered 4wd street and rally cars, based on the Perrin parts that have been in production for... six or eight years? But we're dealing with a whole lot more unsprung and vehicle weight. Also we tend to generate low-speed, high-load impacts where they are mostly dealing with high-speed, lower-load (pothole) impacts.

 

It's not like you can go back to the factory set-up after you have gone this route. It's a one way street and there is no going back once you expanded out the hole.

 

You could go back to stock but it would not be a whole lot of fun. After cutting the bearing housing off you'd have to cut a disc out of 1/4" plate with a hole in the middle that fits in the enlarged hole and weld it in from both sides. Then weld on bearing cups or whatever. It would work fine, and would be virtually as strong as it was originally, but what a PITA that would be! This is why I'm testing before making more....

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Just to chime in here. Ther eare methods to going back to factory options as well if things are completely buggered up. This is the answer I got from Rob when I was dealing with my issues and it put my mind at ease to just try whatever the hell I felt like.

 

Nissan does show to still have the tension rod brackets available for both sides from the master warehouse. (I was surprised)

Part Number: 50260-31G01 bracket, tension, RH

Part Number: 50261-31G01 bracket, tension, LH

 

I can get them for you at 46.91 each. (Nissan List is 64.08 each)

$9.95 to ship both insured ground.

 

These are the 'cups' plus the bracket they are mounted to (which welds to the frame).

 

So if everything goes to hell, simple enought to just reweld a whole new bracket on.

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on my 87 hardbody when the tension rod holes got all wallowed ( is that a word?) out, I had plates cut and new holes punched thru them and than a friend just welded them over the stock bracket, even with out the cup for the bushing they worked fine.

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