Front Axle Drag

Issues pertaining to the TGB/C30X series engine and driveline issues
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AppleTech
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Front Axle Drag

Post by AppleTech » Sun Mar 21, 2021 8:07 pm

I get the feeling my front axle is causing driveline drag. There is a noticeable vibration when starting off which goes away under power. Intermittent clunking when starting and stopping. Very noticeable deceleration when letting off gas. Don’t think the front is locked on as i can steer just fine. Gonna get it up off the ground this week and feel around - any thoughts? Oil good on all portals and diffs and looked clean.

Jim Molloy
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Re: Front Axle Drag

Post by Jim Molloy » Mon Mar 22, 2021 12:27 am

Check the temperature of your brake drums.

Shortly after the arrival of my brother's AluZn TGB 11 from Texas, we drive it to the DMV for the VIN inspection. While en route, I noted a lot less brake action need to slow down for stops. No unussual noises. Once at the DMV office, I checked drum temp and both front were quite warm comaped to rear and the right side are more hot that the left. After letting thing cool for an hour I started back home and used brakes only when absolutley necessary. My first thought was a phenomenon I have seen previously in Unimogs, Volvos and Haflingers. Lamination of the layers in the brake hose oover time.

ALL eight of the flex hoses showed evidence of lamination. The right front ones were the worst. This will cause a temporary one way valve effect for the slave cylinders downstream that tends to resolve spontaneously if the pedal is not actuated for a period on time. We decided to replace all slave cylinders, shoes, springs as well as the flex hoses. Only the flex hoses truly needed the swap.

Hope this helps.

Jim Molloy

AppleTech
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Re: Front Axle Drag

Post by AppleTech » Mon Mar 22, 2021 7:51 am

How would you describe what the lamination looks like? I initially inspected brake lines and they looked just fine to my naked eye...

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rmel
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Re: Front Axle Drag

Post by rmel » Mon Mar 22, 2021 9:36 am

I believe Jim meant de-lamination. See here: http://www.spridgetguru.com/TA0083.html
Puller: 71' 710K 2.7L EFI aka Mozo
Follower: Sankey MK 3, 3/4 Tonne
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Jim Molloy
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Re: Front Axle Drag

Post by Jim Molloy » Mon Mar 22, 2021 6:20 pm

Rmel, Thank you! Yes! DElamination. I was a bit distracted at the time I wrote the note. Thanks for posting that article. It is very well done.

AppleTech, Externally, you will see nothing. The damage is all on the inside.

Take care...and I will be more mindful of my correct vocabulary.
Jim

AppleTech
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Re: Front Axle Drag

Post by AppleTech » Fri Mar 26, 2021 7:22 am

The axle to portal lines on the front appear to be braided steel. Axle to frame are rubber. I'm presuming the braided steel are not original and thus likely not the culprit? Still haven't had a chance to test the theory yet but just thinking ahead - are the brake lines on these trucks fairly standard auto parts store replacements or are they special order?

AppleTech
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Re: Front Axle Drag

Post by AppleTech » Fri Mar 26, 2021 8:41 am

OK took it on a drive this morning for 15 minutes, 50º or so this morning. After drive, all brake drums at ~99º other than passenger front which was ~150º. Need to determine if its dragging due to adjustment or if there is brake line degradation.

Jim Molloy
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Re: Front Axle Drag

Post by Jim Molloy » Fri Mar 26, 2021 12:06 pm

AppleTech,
Many years ago, I took some old lines into our local NAPA and they were able to match with some new production braided steel-wrapped lines. Prefect fit. More recently, I tried the same thing and what came back were NOT correct. I now purchase all my brake components from Tatanka Parts.

The braided lines on your truck are certainly not OEM but they can still age internally. They also may have been made with lower quality materials hidden under a shiny coat. With the dirrential in temperatures in the hubs after driving 15 minutes, I believe you have located your source of the drag.

If you do decide the replace a faulty brake system flex hose, I would highly recomment you make the investment of replacing ALL the flex lines simultaneously. Peace of mind and confidence in your vehicle are priceless.

Take care.
Jim Molloy

AppleTech
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Re: Front Axle Drag

Post by AppleTech » Fri Mar 26, 2021 1:04 pm

Thanks Jim - appreciate it!

AppleTech
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Re: Front Axle Drag

Post by AppleTech » Sun Apr 04, 2021 8:37 pm

Well,

I figured out my drag issue. FWD was stuck on! Fuse #2 blew, which takes out the heater and the FWD control, which fails ON - makes sense.

Has anyone modified the FWD engagement to a cable pull or perhaps vacuum only - no electronics involved? I mean its smart that it fails locked on but I had no real indication other than the driveline drag.

Jim Molloy
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Re: Front Axle Drag

Post by Jim Molloy » Mon Apr 05, 2021 12:07 pm

Great find! Did that resolve the temperature differential between the driver's and passenger side front hubs?
Jim

AppleTech
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Re: Front Axle Drag

Post by AppleTech » Mon Apr 05, 2021 12:24 pm

One brake needed to be backed off - it was creating drag while turning by hand. Doesn’t seem to be any oneway lockup so that’s good. However, now that I backed them off slightly the pedal travels further before the power engages. So I guess I’ll have to adjust all brakes to bring back the good pedal feel.

Jim Molloy
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Re: Front Axle Drag

Post by Jim Molloy » Mon Apr 05, 2021 12:51 pm

Congratulations!!!
Jim Molloy
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http://www.northwestmogfest.com

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