Longfield turning radius

TNFJ40

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Hello, several years ago I upgraded to Longfield 30 spline axles and birfs on my ‘77 40. We ground out the ends of the axle housing as needed for clearance. A few years ago the DS birf started clicking when in full turn. I thought maybe it was just a product issue and replaced it. Recently, the same thing has happened. I don’t put many miles on this truck so now I’m trying to figure out what is causing this.

I have Saginaw PS with a 7” Pittman arm. On the trail I’ve always thought the turning radius was still less than ideal (compared to my 80 series). However, after reseaching some I’m now wondering if my steering travel (turning radius) is exceeding what the Longfields can handle. I dont like the thought of having even less turning radius on the trail but can’t keep replacing birfs.

I ran my steering from lock to lock as limited by the steering stops on the knuckles and it measured 50 degrees. The Longfield literature claims they have 40 degrees of turning travel. I just put my replacement Longfield back on the axle and moved it from one side to the other on the workbench. It measured 72 degrees of travel. I assume that although the birf can physically rotate that far it’s not designed to handle the load when extended that far, correct? My thought is that I need to adjust my steering stops until I only have 40 degrees of travel. Before I do this I wanted to see if anyone has some knowledge on this in case I’m missing something. Thanks for any help.
 

1911

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Hello, several years ago I upgraded to Longfield 30 spline axles and birfs on my ‘77 40. We ground out the ends of the axle housing as needed for clearance. A few years ago the DS birf started clicking when in full turn. I thought maybe it was just a product issue and replaced it. Recently, the same thing has happened. I don’t put many miles on this truck so now I’m trying to figure out what is causing this.

I have Saginaw PS with a 7” Pittman arm. On the trail I’ve always thought the turning radius was still less than ideal (compared to my 80 series). However, after reseaching some I’m now wondering if my steering travel (turning radius) is exceeding what the Longfields can handle. I dont like the thought of having even less turning radius on the trail but can’t keep replacing birfs.

I ran my steering from lock to lock as limited by the steering stops on the knuckles and it measured 50 degrees. The Longfield literature claims they have 40 degrees of turning travel. I just put my replacement Longfield back on the axle and moved it from one side to the other on the workbench. It measured 72 degrees of travel. I assume that although the birf can physically rotate that far it’s not designed to handle the load when extended that far, correct? My thought is that I need to adjust my steering stops until I only have 40 degrees of travel. Before I do this I wanted to see if anyone has some knowledge on this in case I’m missing something. Thanks for any help.

I have had Longfields in mine for 12-13 years, but never measured my steering or turning radius - will be curious to see what you find out.
 
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I would jack up the front end and have someone turn the steering wheel while you rotate the tire to see if you could duplicate the noise. That might give you a better idea of where your stops need to be set.
 
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Looking at travel angle on the workbench does not tell the whole story. Once it is in the vehicle, there is a lot going on with forces from all movements of the vehicle. If longfield says 40 degrees, perhaps they know that those forces at a higher angle can destroy their design. Look at the manual.





knuckle.png
 
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TNFJ40

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Thanks for the excerpt from the manual. I don’t understand what it means when it says 30 deg for inner wheel and 23 for outer. I measured using the face of the knuckle with the hub removed.
 

TNFJ40

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Thinking more about that, I believe they mean the inside wheel of a turn vs outside wheel. So, when making full right turn the right wheel rotates 30 deg and left only 23 due to Ackerman principle. If so, the birf needs to rotate 30 degree in either direction to accomodate. Guess I need to call Longfield and understand what they say their birf will accommodate and how they are measuring it.
 
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Thinking more about that, I believe they mean the inside wheel of a turn vs outside wheel. So, when making full right turn the right wheel rotates 30 deg and left only 23 due to Ackerman principle. If so, the birf needs to rotate 30 degree in either direction to accomodate. Guess I need to call Longfield and understand what they say their birf will accommodate and how they are measuring it.

You are correct. I have not heard that since right after high school. So, even though there is adjustment for the stops, following the manual is probably the safest.


 
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After a while , long fields start to click from wear. I use Moly slip grease and it helps the issue a lot. You are not over steering your axle or pushing the axles beyond their limit with stock knuckles, even if you remove the stops. I believe long fields will turn 37 degrees in either direction.
 
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After a while , long fields start to click from wear. I use Moly slip grease and it helps the issue a lot. You are not over steering your axle or pushing the axles beyond their limit with stock knuckles, even if you remove the stops. I believe long fields will turn 37 degrees in either direction.

First post says longfield allows 40 degrees. So, you are right there with 37 degrees.
 
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cruisermatt

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You’re not oversteering them with the stock knuckles/housing.
How are you measuring 50-degrees of steering ? The housing should only be capable of 41-degrees max and that’s with crushing the felts and retainers.

C3B7AB36-3CB7-4DDA-B1C4-2C3C232F77BC.png
 

TNFJ40

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The 52 degrees was total, so about 26 degrees in either direction. I measured it on the outside face of the knuckle like in your picture. If the numbers that are being talked about are in either direction, I’m nowhere close to damaging the birfs because of turning radius. Correct? That would tell me I should be able to run the stops in and gain some turning radius?? The question is how much can I safely go. As I said earlier, when I rotated the new birf from lock to lock on the workbench it measured 72 deg total (36 in either direction). I just called Trail Gear and asked their tech guy what the 40 deg of quoted range meant. He thought it was 40 in either direction. I told him I was only getting 36 in either direction so he is going to ask the engineer how that is measured.
Something doesnt seem to add up.

The other question is why do these things keep going bad if Im not over steering them? There was still grease inside them when I pulled them out.
 

TNFJ40

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I just spoke with Trail Gear again. The guy said that the Longfield is designed to turn 40 degrees in either direction. I told him that when I rotated it on the workbench it would only go 36 degrees in either direction before it stopped. He said the balls and the cage inside will actually go further but you can't apply enough force the way I was doing it. Based on some past posts that supposedly referenced Bobby Long, etc. I think I will set my stops so the inside wheel in each direction can turn 36 degrees and call it good. On the bright side this will be better than the roughly 26 degrees I've had in the past.

I then asked what would cause me to have three of these units start clicking over the years. He said the clicking noise doesn't necessarily mean the birf is bad, just that the balls have taken a set. When I pulled the units out they also felt very rough. So, I guess I still don't have an answer as to what has caused the failures. If anyone has more info on this topic please let me know. Thanks.
 

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