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NV4500 3rd Gear Issues

Drucifer

Contributor
ORF
Joined
May 6, 2021
Messages
16
Loc.
Santa Rosa
My hard-working transmission has developed a bit of an issue and I'd like to see if any of you all could lend me some knowledge? My bronco has a 302 with a mild build on it, Edelbrock Pro-Flo4 injection, NV4500 and the stock dana20 behind that. My wife an I drive it all over the west towing our 16' Airstream Basecamp. Yesterday, on a quick trip out to the coast while pulling the trailer, I down shifted into third going up a grade and halfway up the transmission starts screaming. To me it sounds like it's trying hard to eat a bearing. This noise is only in third gear and only while under load (coasting in 3rd or steady state driving on flat ground there is no noise).

So, to you NV4500 experts out there. How hard is it to rebuild a NV4500? Is it even worth it these days to do so with it being an obsolete transmission and with the finicky synchros in it? Would I be better off replacing it with something like a TR4050? I'm very mechanically adept and have done all the work to my Bronco so digging into this doesn't intimidate me, I just don't want to be throwing good money after bad. So, what say you?

Bronco and Trailer.jpeg
 

jmhend

Bronco Guru
Joined
Dec 25, 2007
Messages
2,733
My hard-working transmission has developed a bit of an issue and I'd like to see if any of you all could lend me some knowledge? My bronco has a 302 with a mild build on it, Edelbrock Pro-Flo4 injection, NV4500 and the stock dana20 behind that. My wife an I drive it all over the west towing our 16' Airstream Basecamp. Yesterday, on a quick trip out to the coast while pulling the trailer, I down shifted into third going up a grade and halfway up the transmission starts screaming. To me it sounds like it's trying hard to eat a bearing. This noise is only in third gear and only while under load (coasting in 3rd or steady state driving on flat ground there is no noise).

So, to you NV4500 experts out there. How hard is it to rebuild a NV4500? Is it even worth it these days to do so with it being an obsolete transmission and with the finicky synchros in it? Would I be better off replacing it with something like a TR4050? I'm very mechanically adept and have done all the work to my Bronco so digging into this doesn't intimidate me, I just don't want to be throwing good money after bad. So, what say you?

View attachment 874100
I personally would rebuild what you have if I were you. Years ago I rebuilt a T5 transmission in a mustang and that wasn't terrible.

I did a quick search and see a pretty decent Youtube video on rebuilding a NV4500. There seem to be more but this was the first one that I saw.


Good luck with your decision and what a beautiful pair.
 

thegreatjustino

Contributor
Red Head Grease Monkey
Joined
Jan 23, 2002
Messages
15,624
Loc.
Stockton, CA
Talk to Lars here on the board. He rebuilt his NV4500 a number of years ago and had somewhat of a thread on it.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
And I think he still sings the praises of the 4500 after many thousands of off road and on road miles over those years. He is the type of person to go for upgrades when and where they're needed, so may be looking at newer offerings, but seems to me the last time I heard him comment on it, he was still liking the 4500.
I think too that he's commented on the clunky truck-like shifting, but overall not unhappy.

And just like most with weak spots, I believe there are upgrades to ensure you don't have to keep renewing for failed parts.

So now that I've put words into his mouth without checking for accuracy first, it'd be better to hear from him. Hopefully he will see this and chime in.

Paul
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,355
Oh, and great picture too! Thanks for posting that up for sure. Love seeing the Bronco of course, but with family (and four legged family members) and great scenery and the trailer, it's even better.

Paul
 

Apogee

Contributor
Bronco Guru
Joined
Nov 26, 2005
Messages
6,033
I'm watching this thread...I'm debating diving into my NV4500 myself as well versus having a trans shop do it. I need to swap out the main shaft on mine since it was shortened to be adapted to an NP205 in my '77 F150, and now I want to put it in my EB with an ATLAS II I picked up that's already set up for the Dodge NV4500 output shaft. Aside from replacing the input shaft when I first got the transmission from AA ~20 years ago due to shipping damage, the only other times I've been into it were to look into a small rattle in 5th gear which is dangling off the back of the transmission and outside the case, so pretty easy to get to. As for parts, they seem pretty readily available and not too badly priced, so if you're not intimidated by the prospect of diving into such an ambitious project, I'd say go for it (and take good notes so I can ask questions should I opt to do it myself).

Tobin
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,835
I would pull and inspect before deciding on what to do with it. It might be an easy fix. It might be full of fubar.
If full of fubar, now is when to decide what transmission to run. Even that would be a tough call. You already have the NV4500 adaptors. 4050 is an all new option. ZF kinda makes sense as well.

As for why 3rd is the only bad gear under load? Usually it is 5th gear that falls off in these transmissions. A 3rd issue is new to me.
 

lars

Contributor
Been here awhile
Joined
Jun 29, 2001
Messages
3,041
Loc.
NorCal flatlands
It's been ten years at least since I rebuilt mine. Probably more like 14. Biggest issue these days is probably parts availability, especially the synchros. Here's the text of an email I wrote to someone who tracked me down in 2014. quad4x4.com is now https://torqueking.com/ I have no idea if they still support the NV4500.

"My NV4500 was pretty easy to rebuild. I had heard it described as the "last of the easy to rebuild American transmissions". A few details...

I got all my parts from www.quad4x4.com in Montana. The website is not very well organized and is too verbose, but there is plenty of info. That guy's parts are expensive compared to some other rebuild kits on the market, but his parts are all OEM/US made, which was important to me. The OEM synchronizers are carbon fiber. There are Chinese-made brass synchronizers out there but they have a reputation for being junk. That's just one example, then there are bearings, etc.

He offers a few rebuild kit options with various amounts of parts. I don't recall offhand which kit I bought, but I believe it was the most comprehensive one. I didn't want to have to do the job twice. He sells an overhaul manual as well, which is excellent. I highly recommend it. Very well organized (unlike the website) with lots of photos and easy-to-follow instructions.

There are a bunch of special tools for sale on that site, I was told I only really needed one: the mainshaft nut wrench. So I bought that one. Which one you get depends on what your transmission came out of. Mine is an early gas (V8) transmission, so it has the smaller input shaft and 21(?) spline output shaft so I bought the appropriate tool for that transmission.

Other tools required will be some large and small snap-ring pliers, and access to a press. Lucky me, the shop at work has several arbor presses (for r&r of bearings) so that was easy. Also a dial indicator for setting mainshaft endplay. That's very easy to do, it's set up with various thickness gaskets between the input shaft support and the transmission case.

My transmission has never been as quiet as my old NP435 was, and it still isn't. When it's warmed up it sounds like there is some gravel in the transmission when I'm stopped in neutral with the clutch out. But it doesn't hurt anything. Also if I lug it in gear, it will start to growl when I'm on the gas with the engine below 1200 rpm or so.

The 5th gear issue happens when the transmission is behind a diesel. Quad4x4 sells upgrade parts to cure the problem but they are *expensive*. Unless you have a super powerful engine and you spend a lot of time in high-torque situations at low rpm, it shouldn't be an issue. Even then the power pulses of a V8 just aren't as damaging as those from a diesel so it probably still wouldn't be an issue. When I took mine apart both 5th gear and mainshaft were in great shape, and the 5th retaining nut was tight.

It helps to have help. That sucker is heavy. With a friend helping me we were able to pull the transmission, rebuild it and get it back in over a long weekend."
 

lars

Contributor
Been here awhile
Joined
Jun 29, 2001
Messages
3,041
Loc.
NorCal flatlands
All that said... If I was transmission shopping right now with no bias, I'd hands-down be installing a 6R80. A transmission that didn't even exist when I got my hands on my NV4500 back in 2005. If someone told me I had to stick with a manual transmission, then yeah, I'd happily keep the NV4500. I've put 10's of thousands of miles on it since I rebuilt it and it just works. And there is the panache of an old style truck transmission. But I've gotten old and lazy, and the gear splits aren't the greatest. Fortunately my recently installed 408 stroker eases that pain a bit. But just mashing the gas pedal and having all the shifting taken care of is attractive.
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,835
The rattle in neutral is rollover noise. It is the engine rpm pulsing slightly and the the gears rattling. It can sometimes be fixed with a different crankshaft damper (Fluiddamper is what I have heard worked). Different springs on the clutch disk can also tune out that harmonic. Often it is a guessing game. Even so you may still never get it. Doesn't hurt anything, just annoying.
 

BUCKWILD

Full Member
Joined
Jun 20, 2016
Messages
350
Loc.
Butte county
IF I remember and IF I do there is a bearing under third and you now have a bad main shaft and probably a 3rd gear at least. But is has been a long time and lots of transmissions ago
 

lars

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Been here awhile
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Jun 29, 2001
Messages
3,041
Loc.
NorCal flatlands
The rattle in neutral is rollover noise. It is the engine rpm pulsing slightly and the the gears rattling. It can sometimes be fixed with a different crankshaft damper (Fluiddamper is what I have heard worked). Different springs on the clutch disk can also tune out that harmonic. Often it is a guessing game. Even so you may still never get it. Doesn't hurt anything, just annoying.
Old Triumph and Ducati motorcycles do it too. It's endearing :)
 

jamesroney

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Sr. Member
Joined
Sep 11, 2007
Messages
1,667
Loc.
Fremont, CA
I just wrote a long rant about why automatic transmission suck, and why the NV4500 is the best transmission for your Bronco. Then I deleted it.

You are in Santa Rosa. I'm in Fremont. If you bring it here, we can take it apart in an hour. They are easy. You can order the parts you need and put it back together yourself. No special tools for re-assembly.

You don't need synchros. mainshaft is cheap and available. Fix it yourself for a couple hundred bucks.
 

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Drucifer

Drucifer

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ORF
Joined
May 6, 2021
Messages
16
Loc.
Santa Rosa
Thanks all for the replies. I'm going to get to pulling it out this weekend and take a peek inside.
 

jamesroney

Contributor
Sr. Member
Joined
Sep 11, 2007
Messages
1,667
Loc.
Fremont, CA
Thanks all for the replies. I'm going to get to pulling it out this weekend and take a peek inside.
Might want to save the gear oil in a clean container. I like to run it thru filter paper and look at it. Also, it's expensive and it doesn't wear out. Those carbon fiber blocking rings don't like the cheap stuff...
 

lars

Contributor
Been here awhile
Joined
Jun 29, 2001
Messages
3,041
Loc.
NorCal flatlands
I just wrote a long rant about why automatic transmission suck, and why the NV4500 is the best transmission for your Bronco. Then I deleted it.

You are in Santa Rosa. I'm in Fremont. If you bring it here, we can take it apart in an hour. They are easy. You can order the parts you need and put it back together yourself. No special tools for re-assembly.

You don't need synchros. mainshaft is cheap and available. Fix it yourself for a couple hundred bucks.
I, for one, would like to read your rant. Despite my whining about switching to an automatic I generally really like my NV4500.
 

73azbronco

Contributor
Bronco Guru
Joined
Nov 11, 2007
Messages
7,796
Did you run stock mopar nv4500 oil? One of the few mechanical things that is temperamental to fluids from what I have read.
 

jamesroney

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Sr. Member
Joined
Sep 11, 2007
Messages
1,667
Loc.
Fremont, CA
I, for one, would like to read your rant. Despite my whining about switching to an automatic I generally really like my NV4500.
As requested...Automatic transmission rant now available in the Tech section.

 
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