NV4500 Opinions

[allanbr]

I'm Planning a Tranny & Tcase upgrade to my '99 TJ (4.0l) this spring / Summer.  My AX15 slips out of 1st gear and is tough to shift in and out of 1st and second.  My NP231 is also making some noises I'm not fond of when I'm in 4x4.  Both are original equip and are just shy of the 300,000 km mark.
I've got my mind set on an Atlas Tcase (ratio undecided - based on what tranny it mates up to), but I'm on the fence with the tranny.  My bulletproof side says to spend the money on a new NV4500, but the practical side says that installing a new AX15 and taking the time learning to rebuild my current one would be a much cheaper route.    For reference, in time I'd like to bulld my rig up to accomodate 35 -37's (I think the AX15 may have long-term durability issues with 35's +)
Anyone that's done a NV4500 swap care to weigh in on this?  Would you do it again?

And yes, I'm partial to the manual trans.

[vantagetes]

Is this mainly a trail rig or do you do a fair bit of highway driving too? Are you planning on staying with the 4.0 or are you considering an engine swap in the near future?

The AX-15 is going to be much cheaper to replace as there are lots of them around, and while they are considered a "lighter" transmission they still take a whole whack of abuse without much complaint. Same thing with the NP231 just the lack of lower ratios availible for it make most people toss it the first chance they get. You will see some threads here and there about people who have roasted them and want something bigger, but you have to consider what their setup is before you read "the AX-15 is shitty". Alot of those guys are running built up v6 and v8 engines where they are pushing twice the power and torque of a jeep 4.0L engine through their drivetrain.

The only big downside to the AX-15 is that first gear is fairly steep so if you're running a 231 it makes you want to cry. With the Atlas I'd be willing to bet 1st gear would be tolerable in low range, especially if you're at 4.88 or so in your axles.

[allanbr]

This probably won't be a strictly trail rig for sometime, but either way I'd like to maintain highway-ability without spinning at 3000+ rpm to do so.  The wider overall ratio of the NV4500 is attractive for that reason.  Future engine swap? yes, but leaning towards a Golen 4.6 stroker, so not planning on putting 300+ ft-lbs through the trans.
I agree the AX15 seems to get written off as a weak gearbox.  The 300,00okm I have on mine tells me otherwise  and that's why I'm still considering it.   If it only came with a 4+:1 first gear ratio it would be a no-brainer for me.  On the flip side - the NV4500 ends up having such a low first gear ratio it ends up effectively being a 4 speed for nearly everything but off-roading.  And none of this says anything about:
- Installation - Is it really as straight-forward as all the supliers websites claim? 
- Shift quality - I can accept it's not going to be as smooth shifting as the AX15, but to what degree? 

Thanks for the perspective.     

[vantagetes]

You're looking at some light machine work at best and possibly some last minute part hunting as there are so many different variations of parts and configurations you have to account for.

Have you found a NV4500 that is already set up to bolt to a 4.0 or were you going to get the tranny and then look at something like the AA adapter bell housing?

Here's a good read on some of the work you need to do: http://www.advanceadapters.com/downloads/712568.pdf

I also think you need to run at least a 1" body lift to have the tranny fit in there.

[hps4evr]

if you want an ax-15 with a 4 to 1 first gear go with an nv3550. it came in the 1999-ish-2003 tj's. 4 to 1 first, over drive. read up on these swaps on the advance adapters site, and novak adapt site. i think quadratec has complete packages to swap an nv4500 and atlas into your jeep. driveshafts may need adjusting and a body lift may bee needed as well. the nv4500 is a tough tranny but it has its issues as well. ive read about oiling problems and expensive fluids. do some research and decide how much you're ready to spend. if you figure your jeep will spend a lot of time on the highway getting to trails then lean towards anything with an over drive. the 4 speeds are stupid strong but with no OD life at hwy speeds gets annoying.

[allanbr]

Thanks for the input.  I have looked at the NV3550 as a possibility but the 4.02 : 1 vs 3.83 : 1 first gear  difference from it to the AX15 doesn't get you much crawl ratio even with a 4.3:1 or 5:1 T-Case.  I have spent many hours reading everything I can find on Novak,  Advanced Adapters, High Impact trans & gear, NV4500.com etc etc websites, and I still can't make up my mind.   I think the simplest route to go is getting a complete conversion kit from Adv Adapters - The Quadratec & NV4500.com kits are both supplied by Adv Adapters anyway.  Otherwise a guy needs to search out a Dodge truck standard duty NV4500 with1-1/8" 10 spline input to allow the simplest bolt-up to the 4.0.  Any of the other GM or HD Dodge 4500's require additional adapter kits that just use up precious driveline length. Yep I knew about the 1" body lift and that floorpan cutting / patching is required to squeeze this thing in as well as modifying the upper shift tower to get the shift lever far enough back to not interfere with the dash.    I'm still hoping that someone who has done this could give me the full 411.

Thanks again.   

[Elsifer]

A 3550 out of a Rubi will suffice, and bolt right up. The 4500 has a granny low first gear, meant for one-ton diesels. Stupid strong, and you can get one out of a wrecked one-ton, and get the bellhousing from AA. The tail, depending on a dodge or chev, and 4wd or 2wd; parts can be gotten from any tranny shop.

The best is the chev 4wd 4500, with granny 7something to 1 first, and has the 8 bolt setup for marriage to your atlas. Otherwise a 2wd can have the tail swapped over to a dodge 4wd rear setup quite easily. And still keep 5th gear.

The 4500, is also rear-output lower than a 3550. You might need a small body lift to clear the tub. 3550 is wrangler tub compliant.

Both are great tranny's. The 4500 in our monster machine was divorced to the Profab monster-truck drop case, and took a 1st gear clutch drop at full revs out of a bbc454, turning 2.5t rockwells with 49" iroks. If you're gonna go big, the 4500 is your case. If you're gonna stay below 40's, then take the time to find a 3550.

The rubicon 3550 with the 4.1 tcase, and 4.11's in the diffs crawls really nice. Don't discount the 3550.

If you looking for simple, then go 3550, it'll take (if I recall) something like 300hp. So unless you're stroked or sbc/bbc'd, stick to the simplicity.
Otherwise, if big power and big rubber are your goal, go through the 4500 process. Bnine here can help. But there are *lots* of 4500 articles on Pirate.

Good luck!

[Bnine]

   I'm still hoping that someone who has done this could give me the full 411.

Thanks again.    

I run a 4500 mated to a 4.5L custom long rod stroker using an AA bellhousing and slave kit, 2.72:1 Klune V underdrive and 2.0:1 Atlas two speed case.

My 4500 started as a 91 chev 2wd 1 ton transmission. I chose that model for the 6.34:1 first gear, and the 32 spline output shaft. The downside to the 32 spline output shaft unit is length. If you go instead with a dodge 29 spline, the unit is about 2 inches shorter.

I converted my 2wd to  a 4wd using a mainshaft and bearing kit from gear center, and also replaced the shift tower with the newer model square style.

Lubrication is not an issue with 4500's as long as you top them up an extra litre. They are a big case, so people that wheel them and dont know about the extra litre end up starving the input bearing.

Fith gear needs special attention. There is a nut on the output shaft that is prone to backing off. Staking that nut onto the shaft eliminates the back off issue.

The 4500 is very easy to work with due to being a top loader. AX's, and 3550's are a real pain to work on due to design, and harder to source parts for.

A complete install kit from AA should make it pretty simple.

4500's are fully synchro'd and you would be hard pressed to tell the diference between a 3550 and 4500. They are not like the old NP435's and T18's of yester years.

The only real set back to a 4500 is weight. Its a beast at 225lbs, but then again, the strength is there in return.

Also, the height is a bit of a pain. Most my floor is gone because I tucked mine flat to the frame rails.



3550 that came out. I've pulled 4 now that were broken like this due to hard wheeling



4500, klune, atlas



Wheres the beef? In the gears.....duh



The 2wd output and 5th gear. With a 4wd output there is a retaining nut on that top shaft



All said and done my 4500 was about 1200$ start to finish. Purchased, converted, rebuild, and adapted to a 4 litre. Most 3550's go for a 1000$ plus, condition unknown from a wrecker...........

Something to think about.

If you have any further questions, let me know.

Oh yeah, you asked for opinions. I've run 435's, t18's, ax 15's, and 3550's. I love the 4500 for what I do. The gearing is good, and the peace of mind is even better.

[allanbr]

Thanks very much, Bnine.  That's great info.  Sorry I've taken so long to reply.   Probably the biggest concern I have is the install.  This will be my first full trans & tcase replacement and I just want to make sure I'm not biting off more than I can chew.   I consider myself fairly mechanically inclined, but somewhat of a newbie nonetheless.  If a person allows themselves enough time, would you say this is an install anyone could pull off ?