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5Th Gear Locknut


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hey guys and gals, im sure this topic has been beaten to death on here but i have been debating on this 5th gear nut fix for some time that fithgearrepair.com offers. I have right around 286,xxx on my nv4500 and i installed a new clutch at 160,xxx only cause the release bearing was shot, my fault really, i catch myself rollin down the road with my foot resting on the clutch pedal :duh: . With that said, i pull my 21ft nash bumper pull all over the western states and rarely pull in 5th unless i'm on a nice straight stretch going across nevada. There are a lot of claims that if your retaining nut hasn't slipped off yet, it will. ultimatly loosing 5th gear. Would it be wise as a preventative maintenance to drop the tranny and perform the fix or wait till i loose it to repair it? just wanted to gather some feedback and if any of you out there have dealt with loosing 5th or have performed this repair

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224k miles on my Dodge and never touched the transmission yet other than a clutch. I tow all the time in 5th gear. Never had a failure yet and going to continue to tow in 5th gear. I think majority of this issue stems from oversized tires. I got a buddy in New Meadows with 37" tires on his 97 and had 3rd gear syncro fail, 5th gear nut issues, and clutch failed premature. Stock sized tires don't seem to have this issue as much since you not trapping torque against the transmission as much.

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well,   2  thoughts here:     it's made it this far,   and  with your style of  operation,   loosing  5th gear   hasn't been a problem!     I have to think  most  of  the problems   came  from lugging  too much   in  5th,  and   the  harmonics     loosened  the nut. (after  the  splines  are  slightly  worn)     Your  style of  driving  apparently  works!

 

But  then again,        It  might  be  on the verge of    parting ways tomorrow.      Sounds like   that  site you found    has  a pretty good   retainer,  and    you  could have it   installed  without  dropping the  trans.      Did  I read  it  correctly  when they said their  retainer costs  about the same as  a new nut??         If   it were me,  and  getting  thousands of miles  from  home,    I'd probably do it.   Just for  peace of mind.

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good point on both, I don't plan on running oversize tires ever. you are correct on the install, i read it wrong at first. the only thing you have to tear out is drivelines, t-case and cross member from what it seems. It seems like a guy that wanted to check and see if he was having a problem could spend the half hour or 45 minutes it takes to tear it all down that far and remove the extension housing could check the torque spec. on the locknut which is 280 ft.lbs. :think:  or better yet! torque that sucker down to 280 ftlbs and weld ya acouple beads on that locknut, PROBLEM SOLVED  :lmao:   

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I worked at a gear shop for a few years and if you do have a locknut issue there is no amount of weld that holds long term, the only true fix I have seen is to update the mainshaft, if the one the company sells is truely a fix without a main shaft replacement as they calim I would research it heavily before i would spend money on it.

It is easy to remove the t-case and inspect it without tampering with it. If it is still tight then I wouldn't worry about it, you can peen the threads behind the nut to keep it from working off as fast if it were to come loose.

Key sentence taken from their site.........

"If installing this retainer because of 5th gear failure, be sure to inspect the main shaft splines to make sure that no damage has been done by the break down. If damage has occurred be sure the transmission is repaired properly first."

This is the problem with all aftermarket solutions other than mainshaft update, if the nut has been loose most likeley the shaft splines are worn and will not hold any nut even with a helper fix.

Edited by Wild and Free
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agree  with  WF.    I've  seen my neighbor  weld up  that   nut,  not just  tacked,  but  full  circumference  weldment.    

shoot,  it  didn't make it   a year.       But  he did it after  3 or 4 attempts.   (lock tite,  double nutting,   drilled  and   pinned,  then  total welding)  each   attempt  would last  maybe   10 k   miles... lord only knows  how much   slop  he was  dealing with!

 

 

I am surprised  he  didn't  bust the  shaft after all that   drilling,  welding.....      

I wouldn't  back off the  nut to retorque... just    make sure it's   still  @   280,   then  go just enough more to index  the   retainer.

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Welding the nut doesn't work.  The "fifth gear repair"

 

http://fifthgearrepair.com/nv4500repair.html

 

May work.  Dude says he's never seen a failure.  If you look at the way the part is made, it seems pretty obvious how it works.  However, I doubt I'd perform this fix preemptively unless I already had the transmission out.  In most cases, when the nut goes, there's little damage other than a loss of fifth gear and maybe damage to the mainshaft which is a $120 part.

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  • 2 weeks later...

Welding the nut doesn't work.  The "fifth gear repair"

 

http://fifthgearrepair.com/nv4500repair.html

 

May work.  Dude says he's never seen a failure.  If you look at the way the part is made, it seems pretty obvious how it works.  However, I doubt I'd perform this fix preemptively unless I already had the transmission out. 

 

I used this repair on mine......for $150 and my labor, I figured even if it failed I was only out a little, compared to the cost of disassembling the trans to put in a new main shaft (which is in fact the best fix for the problem). I did pull the trans out for the repair......but I had a new clutch waiting on the shelf anyway. They do say that you can install the sleeve with the trans in the truck though.

It's been in there for probably 40k+ miles now, daily driving and towing 8k-12k (and I do tow in 5th) with no issues at all, so I have to say it seems to be a good repair option.........

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