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Idler arm problem - nut spins freely way before proper torque was reached

86-95 Trucks & 4Runners 2nd/3rd gen pickups, and 1st/2nd gen 4Runners with IFS

Idler arm problem - nut spins freely way before proper torque was reached

Old 03-16-2019, 09:29 AM
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Idler arm problem - nut spins freely way before proper torque was reached

The nut is obviously fubared at that point...
I'm stumped. I thought all the idler arms are the same dimension: at the ball joint where it enters the steering relay rod, it's obviously too thin and enters the rod too deep - or the nylon locking nut is a POS.

Proper part number (from toyodiy) 45490-39245

The one I ordered:

https://www.ebay.com/itm/HERTH-BUSS-JAKOPARTS-Lenkzwischenhebel-Lenkstockhebel-TOYOTA-4-RUNNER-HILUX-II/183006078909?epid=2008777700&hash=item2a9c0327bd:g :Q2kAAOSw9NhbFtcK

Supposedly a good brand too

Anyone experience this? Are there different ones?

​​​​​​What aftermarket brand should I go with? Moog?
Is the oem part really needed?
https://www.toyotapartsdeal.com/oem/toyota~arm~assy~steering~idler~45490-39245.html?Make=Toyota&Model=4Runner&Year=1986&Sub model=&Filter=(d=USA;1=22REC;3=T1;4=SR5;5=MTM;6=5F ;7=RCB;8=W;9=HLF;10=ST;12=EFI;13=CBU;0=RN61L-MSEA)

Last edited by ev13wt; 03-16-2019 at 10:30 AM.
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Old 03-16-2019, 10:07 AM
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This is the current booty fab, so I could get it home.
How high are my chances of dying?

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Old 03-18-2019, 03:14 AM
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I haven't taken it apart again, but I think I just got some really bad brand.

I've decided to loctite it and order one of the recommended arms from RB, or the one he has in stock: https://www.4crawler.com/4x4/ForSale/IdlerArm.shtmlWhy just support those idler arms?

Good question! There are two main reasons but before getting into them it is important to point out that 1st and 2nd gen idler arms are interchangeable. The second gen arms are typically stronger though. Therefore, if you have a 1st gen truck, it make sense to install a 2nd gen arm for the added strength.

First, for the most strength, the largest shaft diameter is the key factor. Initially we assumed that we would want to at the very least produce idler arm bushings for the high-end Napa arm as well as the OEM arm because we assumed they would be the best. After an idler arm spending spree we found some interesting things we'll discuss below. ***CHART OMITTED, see original source*** *As you can see, the arms with the largest shaft diameter are at the top of the chart. And that larger diameter equates to almost 11% increase in stiffness over the OEM part, since the torsional stiffness increases by the 4th power of the diameter. Another interesting note is that the Napa 1032403 which has a diameter similar to a 2WD OEM arm is also sold for 4WD trucks even though from a strength standpoint, this arm is below spec., in fact it is about 25% weaker than the FA5040 arm.

We also wanted to support shafts with high manufacturing quaility, such factors as fully machined surfaces. Some of the shafts are only partially machined. A stretchy plastic bushing can be jammed in place with no problem, but this makes fitting a rigid bronze bushing impossible. The part of the shaft closest to the arm itself wears more than the rest. This means that a bushing that fits snuggly over the lower part of the shaft will not fit at all over the rest of the shaft. Assuming one was to verify that the shaft has a uniform diameter, there is the issue of calibration. My calipers might not measure out like yours. As a result it is difficult to machine the parts to order due to the tight tolerances in this application. To reduce part cost it is necessary to produce many at once and supporting one arm helps us accomplish this goal.

Given these issues we have decided to support the most affordable yet strongest idler arms.


(*) One thing to beware of is that sometimes, you'll get an arm in a box marked "FA5040". But be sure to check for a genuine FA5040 arm before taking the box out of the store. The genuine item is marked with a single "L", as noted below. The genuine arm is also in a nice shiny black clean finish. The imitation "iak9424" arms are in a rough dark gray finish, like they were taken directly out of the sand mold and into the box.

If you see a "555" stamped on the idle arm itself (click here for a picture of the stamping), that is likely a Sankei 555 arm, which is actually a smaller 2WD arm. If you find a "555" stamp, take that arm back and swap it for a genuine FA5040 arm. And you might want to be wary of on-line sellers, like on eBay, as you'll not be able to inspect the arm until it is shipped to you. If it is the incorrect part. you may be stuck with shipping it back for an exchange.

Also, some Duralast FA5040 arms have a casting mark of "iak9424 L (click for picture of stamping)" instead of the plain "L" on the genuine FA5040 arm (click for picture of genuine FA5040 arm). The Pro-Forged arm also has "YN130" stamped onto the top of the forged arm section. This "iak9424 L" arm has an undersized shaft, comparable in diameter to the 2WD arm and appears to be a lower quality part. So be sure to check for that when you get the arm. Best bet is to pick one up at your local FLAPS where you can open the box at the counter and verify you are getting the genuine article before leaving the store. Note that some parts catalogs list a Duralast FA1739 arm for certain model years. This arm while the same overall mounting dimensions as the FA5040 arm, has a lower quality casting and the arm shaft diameter is poorly machined meaning that it is difficult to get the bronze bushings onto it. So ignore the parts catalog recommendation and go with the FA5040 part. And this also applies to the Napa-ATM-103-2403 idler arm, if it has just the "L" casting mark, then it is likely the "good" version, otherwise, it is likely a version with a different diameter shaft. THe only way to know for sure is to remove the shaft and measure the diameter.

(**) The Pro-Forged idler arm has the larger 20mm dia. shaft, this is a good thing. However, the inner diameter (ID) of the bushing seats in the "L" cast housing is a bit smaller than the FA5040 arm. Two options are to use a Dremel with a sanding drum or grinder wheel to remove a few thousandths of an inch from inside the housing until you can fit the bushing in place. Or we can custom machine the bronze bushings to fit that housing for an additional cost. See below for ordering options on bushings and idler arm kits. Now there also appears to be a new model of this arm that lacks the "L" in the casting, but instead has a threaded hole for a grease fitting where the "L" used to be. This arm housing has the same bushing seat ID at the original FA5040 arm and thus will accept the regular bronze bushings, although you may need to do a little touch up sanding on the ID of the arm housing to clean up any burrs. So you can order those or you can order our "Pro-Forged" bushing kit and specify you want the full size bushings and we'll add in a grease fitting that fits the hole in the arm housing. Or if you order one of our Pro-Forged arm kits, we'll throw in the grease fitting, which Pro-Forged sometimes omits. Unfortunately we can't guarantee which arm you'll get as they both have identical part numbers and what shows up in our order is what we have to work with. So if ordering a Pro-Forged arm from another supplier, best advice is to wait until you have it in hand then see if you have the "L" casting or the grease fitting hole befre ordering bronze bushings. We are simply reporting the findings of our product research and trying to pass that on to our customers. Pro-Forged also lists a 102-0052 model arm for some model year trucks. If anyone has had a chance to measure that one, let us know the arm diameter. The listing has the same photo as the 102-0045 arm, so it may be an identical unit, if so, it will likely work with the bronze bushings.

So the bushings are built with an inside diameter (ID) of approx. 0.787" (20mm) and an outside diameter (OD) of 0.941" (~23.9mm) to fit over the idler arm shaft and inside the idler arm housing. So the acid test is to measure the diameter of the shaft inside the idler arm, and you need to take it apart to do that. If you lack a micrometer or calipers to do that, wrap a piece of paper or masking tape around the shaft then slice that where it overlaps. Take that paper or tape off and measure the length, a 20mm shaft will measure just short of 63mm long, a 19.5mm shaft will measure just over 61mm long.

Now if you are stuck with an idler arm with the smaller 19.5mm diameter shaft and want to use the idler arm bushings, there is an option. You can obtain some brass shim stock of the appropriate thickness to make up the different in diameter between the shaft and bushing. We can supply such shim stock if desired. It can also be ordered with the bushings if you are unable to check the size of your idler arm shaft prior to ordering. The piece of bushing stock will be cut to ~60mm wide to roll into a ~20mm dia. circle and will be approx. 6" / 150mm wide to allow it to be trimmed down (with scissors) to just fit from the top to the bottom of the idler arm housing. This way the coiled up shim stock will sit inside the housing and bushings and the shaft will fit down inside that shim stock. This should allow most of the 0.767" / 19.5mm idler arm shafts to fit. You may need to do some light filing/sanding of the housing to fit the OD of the bushings if needed. We can supply either 0.009" or 0.004" shim material. The 0.009" shim will make up the 0.5mm difference in one layer, the 0.004" will include enough material for 2 layers, giving flexibility to handle shafts slightly over 19.5mm. Either piece of shim stock is US$10.00 plus postage or $9.00 additonal when ordered with the bushings, specify your thickness preference in the Special Instructions to Seller section of the order form.

Last edited by ev13wt; 03-18-2019 at 03:16 AM.
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