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NV 4500 transmission


Wes806
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Also found this in the shop.

Guess that's two votes for the 75w85 synthetic? 

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Amsoil makes an oil for it as well. Last time I bought some it was a little bit cheaper than from GM or Mopar. 

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I have had good luck with the Napa synthetic 80/90 or whatever the number is. As long as it’s a synthetic and that weight range. The fiber synchro discs can’t take regular gear oil. I honestly think hytran or  hygard would work well in them also. The oil wont ruin the bearings or shafts but wears the synchro fibers. There is a olde ihc truck trans model that needs 30 weight motor oil or it will seize the low reverse gears, and old cast iron  Chevy transfer cases if you put gear oil instead of 10/30 would stretch , wear the chain. Pics of the synchro and other of main shaft or rebuild kit. I bet between my truck buddy and just everyday rebuilding has to be almost a 1000 4 speed,5 speed, 9 and 13 speed plus auto trans I have been into

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9 hours ago, Wes806 said:

Mader I like the looks of your truck.  Nice to hear about how good your  and others older trucks have held up.  I'll be the first to admit that my old Dodge has beaten it's way though many snow drifts where I should of went got tractor and loader.   It has done good by me.

It's quite the upgrade...i can talk on the cab while towing. Load all my crap and still have 8 feet of bed...

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19 hours ago, dale560 said:

You have to use synthetic oil in them or it will burn the synchro fibers up. You can smell a trans with gear lube in it when you pull them hard. A Chevy used the same transmission with different input and a balancer on output drive. Chevy didn’t have enough power to loosen 5th gear. Again whatever you do synthetic gear oil is a must.

I think I always used Mobil 1 synthetic in my NV4500. The 1992 Chevy used the NV4500 trans and it did not use a nut on the countershaft, it used a snap ring, and the 454 didn't have enough power to hurt it, but a turned up 6.5TD will. I lost fifth gear towing when the snap ring broke, I had to disassemble it to get all the pieces of the snap ring out. Dodge used the NV4500HD which had the nut holding fifth gear on. I was told the Chevy NV4500 and the Dodge NV4500HD used different gear ratios also. I wish the NV5600 six speed would have been available in that 1992 Chevy 6.5TD, really like that transmission in the Cummins powered Dodges.

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7 hours ago, ThirdGenRed said:

I think I always used Mobil 1 synthetic in my NV4500. The 1992 Chevy used the NV4500 trans and it did not use a nut on the countershaft, it used a snap ring, and the 454 didn't have enough power to hurt it, but a turned up 6.5TD will. I lost fifth gear towing when the snap ring broke, I had to disassemble it to get all the pieces of the snap ring out. Dodge used the NV4500HD which had the nut holding fifth gear on. I was told the Chevy NV4500 and the Dodge NV4500HD used different gear ratios also. I wish the NV5600 six speed would have been available in that 1992 Chevy 6.5TD, really like that transmission in the Cummins powered Dodges.

The problem with the dodges was with the main shaft-  not the counter shaft.  Having had both transmissions apart I don’t remember either of them having a nut on the counter shaft. As far as my memory serves me the only thing heavier in the dodge trans was the input shaft. 

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On 7/11/2021 at 3:07 AM, sandhiller said:

Problem wasn't the fifth gear nut.

It was the shaft under fifth gear was only splined for half the length of the gear allowing it to rock back and forth slightly causing the nut to back off. And as @Gearclash said towing heavy in 5th magnified the problem.

I tried the set screw nut (worth about 5K miles) then tack welding the nut (worth @15k miles) before failure again.

Finally bought a fully splined main shaft which cured the problem. About 200K with no failure so far.

I use Castrol synthetic.

I have dealt with other machines with the same spline-and-nut arrangement.  If there is any mount of lash in the splines, plus a reversal of the torque through the assembly, it is impossible to keep the assembly tight.  

When I fixed the 5th gear behind my Dodge Cummins, I did get the updated mainshaft nut, but not a fully splined shaft.  When I installed the gear on the mainsheet, I coated the splines on both halves of the assembly with the “Quick” JB weld.  The idea was to make the the shaft and gear assembly act as though it was fully solid.  The “Quick” version of JB weld weakens at a temp low enough that if disassembly is ever required, the heating won’t damage the gear or the shaft, but the heat required is higher than what the trans ever would get to.  New Venture really should have used a tapered spline in that situation so there was a press fit to hold the gear in place.  

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1 hour ago, ZG6E said:

The problem with the dodges was with the main shaft-  not the counter shaft.  Having had both transmissions apart I don’t remember either of them having a nut on the counter shaft. As far as my memory serves me the only thing heavier in the dodge trans was the input shaft. 

Ok, did not have a Dodge NV4500HD apart, so I assumed they put a nut on the countershaft to keep the countershaft fifth gear on. This Chevy NV4500 broke the countershaft snap ring and the 5th gear synchro assembly slid back resulting in no fifth gear. Once I tore it apart to find all the pieces of the snap ring and replaced the snap ring with the one from the Chevy dealer, it was not pulled hard in fifth gear anymore and no more problems. I am surprised the Dodge NV4500HD hasn't had problems with the countershaft snap ring. 

I looked online to see what the differences in the Chevy NV4500 and the Dodge NV4500HD gear ratios were. What I found out was that starting in 1995 the Chevy and Dodge used the same gear ratios, before that, Chevy NV4500 transmissions had a lower first gear than the Dodge NV4500HD. I suppose they figured the V8 diesel didn't have as much low end torque as the inline six diesel did?

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4 hours ago, Gearclash said:

I have dealt with other machines with the same spline-and-nut arrangement.  If there is any mount of lash in the splines, plus a reversal of the torque through the assembly, it is impossible to keep the assembly tight.  

When I fixed the 5th gear behind my Dodge Cummins, I did get the updated mainshaft nut, but not a fully splined shaft.  When I installed the gear on the mainsheet, I coated the splines on both halves of the assembly with the “Quick” JB weld.  The idea was to make the the shaft and gear assembly act as though it was fully solid.  The “Quick” version of JB weld weakens at a temp low enough that if disassembly is ever required, the heating won’t damage the gear or the shaft, but the heat required is higher than what the trans ever would get to.  New Venture really should have used a tapered spline in that situation so there was a press fit to hold the gear in place.  

jb weld sounds like a good idea.

I knew I'd be driving this pickup a long time so just went with the fully splined main shaft and a new 5th gear.

Buy once cry once and forget it.

I found the old fifth gear. You can see the shiny/wore part of the splines that rode on the smooth/unsplined part of the main shaft.

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Here is a pic of the the original main shaft from the repair manual. You can see if you look close how the splines in the gear wore into the smooth part of the shaft.

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And here is the fully splined replacement main shaft.

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IMG_20210711_164914770.jpg

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Yeah, yours is pretty worn.  That was all-around  a dumb design right from the start.  Partially splined shaft instead of fully splined.  And if you note, the thrust load from the countershaft gear is bearing almost entirely to the side of were the mainshaft gear drives the mainshaft splines.  The whole deal was guaranteed to rattle loose.

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