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Old 10-02-2017, 10:36 AM   #1
Tiger Joe
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Location: South of Pittsburgh
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nv4500 swap issues

just got done restoring our 70 C-30. swapped an nv4500 in during the process.

bought the trans used last year. did not get to see the trans operate(other than shifting it on the floor) before we bought it.

issue- trans grinds going into 3rd on the unshift. downshifting from 4th to 3rd its damn near impossible to get it to even go into 3rd (almost like you hit a wall when shifting). trans shifts perfectly into every other gear and shifts fine when truck is off.

yes i purchased the correct fluid.

am I correct in thinking the 3rd gear synchro is probably toast? could there be anything "stuck" with it sitting for well over a year? anything I can do/check other than just pulling the trans?
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Old 10-02-2017, 01:18 PM   #2
mongocanfly
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Re: nv4500 swap issues

copied this.....
NV4500 manual transmission grind going into gearSyncro rings are a common wear item on NV4500 manual transmissions. With this wear, the ring loses friction and will result in grinding during shifting. Chipped teeth in the shift colleen, where it engages in the teeth of the gear, can cause grinding. Forcing the transmission before the syncro has caught up can cause the problem. Incorrect fluid will have a large effect on syncro ring, shifting performance.
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Old 10-03-2017, 10:33 AM   #3
B. W.
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Re: nv4500 swap issues

Sounds like 3rd gear synchro is gone. There is at least one company that offers brass synchros for the 4500 rather that the composite (brass/carbon fiber). I have not used them & don't know how well they work, I'd do some research but they sound better than the carbon fiber ones. (less prone to failure & special lube not required) But I'd talk to some guys that rebuild these.
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Old 10-03-2017, 01:18 PM   #4
Tiger Joe
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Re: nv4500 swap issues

I spoke to one rebuilder yesterday and he suggested we need to drive it more before committing to a tear down.

I guess there is a small chance the synchro could be "stuck"? We bought the trans in Feb 2016 and it sat until a week ago. who knows how long before we bought it that it was out.

going to try to get out on the highway and heat the fluid up some.
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Old 10-04-2017, 01:35 PM   #5
snj8198
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Re: nv4500 swap issues

3rd gear in my 5 speed has ground since new but it does go into gear easy enough. I used the right oil too. Expensive stuff.
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1971 GMC Longbox. Full Roller Stroker 489 w/ FiTech EFI, Chris Straub Cam/NV4500/205/D60/14B w. Grizzly Locker and 4.11's. 2" Lift on 33's
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