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Nv 3550 On 4 Angry Squirrels.

80K views 337 replies 21 participants last post by  Mr.ThunderMakeR 
#1 · (Edited)
Ok. I am starting my new thread that will re-appear from time to time to chart my progress, and or set backs, or complete withdrawal from this project all together. However, I will put my best foot forward with pictures and give it my best shot. If I do withdraw, I will state why, and give notice. But I do not plan on doing that, and my progress will be over a period of time. There are kits out there for sale to do this, so I am following their guidelines, only I am buying my own parts that they list to do it, to save money of course. And I have a major part of the list of things needed already. So, I am starting my thread to start monitoring my own progress and take notes for myself. This application works for ax15 transmissions as well, however, I happened to stumble across a new nv3550 for an excellent price, so I jumped on it, and that is what I am using. I hope this is of interest to all of us blessed 2.5 owners as most of you 4.0 owners are probably just going to shake their collective heads side to side and ask, "why doesn't he just swap to a 4.0?" The answer is, all the things I have make it more cost effective to just stick with my 2.5. I already have the necessary 96-98 dakota bell housing, for 2.5 to mate with the ax15 as they did with the dakota pick ups back then, and it will also work with the nv 3550 as I am using. I have the new NV 3550 transmission, I have the 23 spline np231j dated 1997 that is necessary to work with the trans. as the one on it I have now is a 21 spline. I just bought the clutch disc that is needed to work with my original clutch. p/n cp4198 (autozone) 9 1/8 o.d. but splines to match my nv 3550. I am going to order from Advance Adaptors a pilot bushing p/n (716167) nv4500, and a slave kit p/n (716340) that is said to work with my jeep hopefully tomorrow. The pressure plate and flywheel are also new as well as the Timkin throwout bearing. I do plan on putting a slip yoke eliminator kit, jb conversions, and obviously a new rear drive shaft. Not sure what kind yet. I need it as the new transmission casting is 2 inches longer than the ax5. Well, let me get started with something I really don't like what I see already..This is the disc required to work with the original clutch. the o.d. looks right, the splines look right, but, I noticed the side view angle, the spline column for the ax5 disc appears to be taller. I haven't measured it, but that's what it looks like. My first thought is just to add a properly sized washer to make up for the difference but I am not sure about that yet, or even if this really matters. But I need to know. This clutch disc is an application originally for a 4 cyl. camaro, 1984.
 

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#323 ·
"Box of Rocks" :D Does it shift properly? I know these things are noisy. That is one of the main complaints with it. I have heard of some who take it to the shop only to be told it is normal. I think it is the idler gear especially in neutral right? Or is it more than that.
 
#324 ·
Yeah, it's the idler in neutral. It has actually gotten a lot better after driving it for a while. I've gone about 1K miles on it now, and it's hardly noticeable anymore, so there's definitely a break in period with a band-new tranny. When I first drove it, however, I swore something hadnt been put together right in there. Whenever you would do any hard acceleration, you were certain the thing was about to come apart any second. Also, you might want to change the fluid out after the first few hundred miles, and clean off the magnet on the drain plug. There's some shavings that will come off during the break-in period.

I think the design must share some similarities with heavier duty tranny's. Whenever you hear a semi at a light, you'll notice that exact same idler noise. I never hear it in car tranny's, only big trucks. Guess it's inherent to that class of transmission. Just speculating here though. I hardly notice it now though. Kinda cool sounding, if you ask me...:D
 
#325 ·
Oh yea, with the Royal Purple Synchromax, it shifts like a dream. Occasionally though, it'll pop out of second. Just make sure you really pull the shifter all the way back. My shifter bumps a little on the plastic console too (only 2nd gear), since the whole tower is now an inch further back. Even without the consol installed, however, it would still pop out of 2nd occasionally. Luckily I dont do any street racing in my Jeep, or that might be an issue... :p
 
#326 · (Edited)
This a truck transmission for sure, somewhere between medium and heavy duty. A different animal than the meager ax5. Thanks for the heads up on your experience converting your TJ, and your description is excellent, it is a motivator. I look forward to having a truck transmission in my jeep. (the way it should be).
I will be continuing my experience on converting my YJ and documenting it here of course. Because of your major contribution to this thread, I would think this thread should also be under a f.a.q. in the TJ forum as well. I looked briefly and did not see it there. There has to be a lot of TJ 4 cylinder owners that would benefit greatly from the info. you have provided as well (of course yj owners as well), and I think it might not be a bad idea to have this thread there.
Probably most do this conversion without the Dakota flywheel and clutch by retaining most of the ax5 clutch parts. As I have presented it, and you have done, and completed it, I think it makes it a more fundamentally accepted conversion, as it is basically more the way Chrysler did it with the 96-98 Dakotas. We of course are stepping it up a little by adding the more burly NV3550 as Chrysler did not in the 96-98 Dakotas, and changing out the disc.
This thread provides info. for retaining the ax5 clutch parts, or totally converting to the Dakota clutch system, and of course with the exception of converting the clutch disc, no matter which way one decides to do the conversion. It has proven to be successful and acceptable either way one chooses to do it.
I will use Royal Purple Synchromax when mine is ready. Good info. thanks again.
 
#328 ·
Lol, yea, I've never heard anything like his show. I think early on he was out of Florida I believe, not 100% on that though.
You know I thought my ax5 would be crapped out by now, amazing enough, its still going at approx 297,000 miles just fine (the ax5). I need to put the JB conv ss/sye in my extra 23 spline t- case, just get it ready. Money is not the problem, its just this thing keeps going and going and going. Thanks for checkin here though RollinThunder, things are well, I will be posting my conversion here for the YJ, when the time comes.. When exactly I am not sure. How is everything with your jeep now-a-days?

Edit in 06/05/11 Bush_coon and his stated experience with his 1991 2.5 yj, and how he installed a tj driveshaft with his 2.5 engine, 1996 2.5 dakota bell housing, ax15 conversion, non sye transfer case, in quote below. He stated the manual transmission /2003 TJ/ 4 CYL- drive shaft. He did an AX15 conversion, however, the NV3550 shares the same length dimension as the AX15.

I have discovered that a drive shaft from a 2003 TJ with the 4 CYL DOHC fits perfectly without the SYE set up, just for reference.
http://www.jeepforum.com/forum/f12/ax-5-ax-15-swap-pilot-bushing-question-1213502/
 
#329 ·
Today at Home Depot, I found this 5/16ths round rod. It is something they stock. 36".
It costs 5 dollars. I found the end caps of the slave pins fit perfectly, so you can fabricate your own very easily. I will be creating my own throw rod that will fit perfectly with my slave cylinder. Approx 1" longer than stock length. Made by Crown Bolt-161541.



Some pins I fabricated today below. Looking for approx 1" or a bit more longer, than original. So I have a few different ones cut now.
 
#330 ·
I am using a transfer punch set to locate the centers, just close enough, to use as a pilot for drilling. I am going to take my time with a hand drill. The metal is soft, not difficult to cut through.



All this does is locates the transfer case in the original Yj position, as opposed to the tj position.
 
#332 ·
This transmission is burly, and physically larger than the ax5. Some have reported they have been able to fit it in the original shifter tub holes without trimming the tub. Setting mine up in there to get an idea, I have trimmed my tub some to allow for an easier fit. Approx 2 inch area behind the original shift tub holes.
 
#333 ·
I am going to be posting a few images of the clutch I am going to use. I stated earlier in this thread that I am going to use the primarily Dakota clutch system. I am not going to do that, at this time anyways. I am in agreement with RollinThunder that it really does not matter that much in his view. Though, I think the dakota pressure plate might be slightly better, its probably negligible. So the 20 dollar advance adapter bushing I am using in my ax5 flywheel, with the ax5 pressure plate, and the converted clutch disc, with the original throughout bearing as well. One thing to take note on, is the AA bronze bushing fit fine when not inserted into the flywheel, but as soon as I pressed it into the flywheel, the I.d. of the bronze bushing was compressed some, enough to be a problem for the input shaft to fit into upon install. I have since honed the bushing out just a little, until a nice fit was established which was done with a fine cylindrical sandpaper rotary tool bought at Harbor Freight Tools for ten bucks. It did not take much, just a tad bit of honing. Again, with fine sandpaper tube fittings. At first, the pilot on the input shaft would not even go into the flywheel bushing, but again, that was an easy fix. (just take flywheel off of the engine after you press the bronze pilot into it, and test it on the input shaft of the nv3550)
Just like RollinThunder, I had an old pilot bushing alignment tool hanging around that did not fit the splines for the disc, but the o.d. was there for a snug fit, and the pilot centering was too small, so I wrapped electrical tape around the pilot tool tip to bring it to .750 for centering in the pilot bushing. So I made the old alignment tool work excellent. I also soaked the pilot bushing in oil for quite a while.


 
#334 ·
Today am swapping in a 23 spline compatible gear for the t case. I know its been mentioned before, if you have a complete 23 spline t case ready to bolt up, you will save yourself more work, and time. This is the second time I popped open a t case, its not real difficult, just time spent, that's all. Lots of gasket seal to clean up and re-apply as well.

There are some good 231 write-ups out there. I am not going to go into all the aspects if this because of that. But, I will discuss a few things regarding my experience. Get a good set of transmission snap ring pliers, not the small ones, the larger ones. There is a snap ring that holds the gear shaft and keeps it in the case. When you remove the 4 ten mm bolts and remove cover, you will see it. I set my case half as you will see in the image facing down. Put some rags, or something under on the inside to catch the planetary. Apply the pliers to the snap ring and expand the ring enough, the weight of the planetary will simply pull it down by its own weight, and its out. I find it works a lot better than trying pull the ring off the shaft. Just let the shafts weight do the work. Again, it works excellent. In the above image, there is a larger clip ring that needs to be removed. When you look into some write ups on that ring, some say it is troublesome. I found it easy to remove with small a small pic tool set, basically another harbor freight tool item, they look like dental tools with various angled pic tipped instruments. Made quick work of this, real easy.


Regarding planetary gear swap compatibility, this seems to be a subject of its own. Through some research I will explain this as best as I can as follows.
It is my understanding that the gear cut changed somewhere mid stream 1994. I do not think you can see the difference with the average eye. But your t case will know the difference, and you will hear it, and more. So, I found that three sets of numbers that can be found on the t case circular tag is deemed to be compatible with the post 95 t cases. If your 94 or 95 case has any one of these numbers, it simply means the gear cut is compatible with post 95 input t case gear shafts. I am putting a 97 t case gear in my 95 t case.
52097894
52098361
52098540

So, on my t case, on the image above, the tag shows my t cases assembly number, which is 52098361. What that means to me is that it is compatible with post 95 np231/ 23 spline shafts, as my replacement shaft is from a 1997 np231 t case.
To quote another source; Because of the differences in the cut of the gear, as a general rule, one should not interchange 1987-1993 gears with 1994-present gears.
But that is stated as a general rule, not a definitive delineation.
A good website that discusses this subject is here: http://www.novak-adapt.com/knowledge/np_nvg_input_gears.htm I have the later narrow bearing late gear cut on my t cases. One Thing I don't see mentioned though, is the case bearing that supports the gear/shaft. I had to swap out the case bearing with the shaft. They both are the narrow bearing style, but, there was too much play for shaft fitment into the bearing housing I.d. NVG states 40 something input gear variations, and swapping these gears has been described as elusive, and tricky by another source.
I have spent way too many hours on my T-case alone. I had to pop it open a second time to swap the bearing after noticing the above mentioned problem. I think its right now, but its concerning. This is why I am stressing get a complete 23 spline t case ready to bolt in at the same time, or before the swap if you can, and do your best to avoid splitting the t case for an input gear swap.
 
#335 ·
Here is a 1995 Yj factory skid plate. The top slots fit my ax5 transmission mount bolts. (top slots are closer to front of jeep)

Below, in this image, are the rear slots on the skid plate. At this time my engine is still supported, so its raised up a little from dropping onto the plate. But, the nv3550 is now installed onto the engine. This is where the mount is going to, and does, rest on the skid plate, right in the center of the rear slots, a perfect fit on the plate.

Below is an image of where the shifter housing rises up through the tub floor shifter hole. It comes very close, and rubs up against the metal around the rear side of the hole metal shift boot securing ring. You might want to trim about a half inch off selected areas, but more than that right now seems unnecessary. You will want to remove the shifter stub housing on top of the transmission, the.4 small bolts, as it will get in the way when its time to put the transmission up in there. Not a big deal, just bolt it back on when transmission is in place. I did more cutting than what was necessary to the tub, but that gives me a little more view down there from topside I guess. The metal flap actually is down about an inch more than what you see in the image, I cut it on one side, and it is flapped.up a bit. And what you don't see is about 2" that I notched out behind the shifter in the tub, behind that flap.

Below is an image of how my stock four cylinder exhaust bracket worked out mounting into the ax15 torque arm bracket. It fit right into the bushing to support my exhaust pipe. I was surprised at that. It was a good thing to see how that worked out.

Below is an image of the torque arm bolt holes in the ax15 plate, and in the skid plate below it. They align perfectly, the only thing I need to do is put some washers in the topside of the skid plate under the bushings. Fits really well though.
 
#336 ·
I have updated my IMG codes for photos that were not showing up. Anyone is welcome to inform me if I have missed any in this valuable thread, or in any others. My apologies to Moonshinefuel for having left these holes in his FAQ thread. :wave:
 
#338 ·
Bump!

You guys still around to answer some questions? I'm just beginning a similar swap on my 91 YJ, except I'm doing a Rubicon Tcase as well, so its AX5/NP231 to NV3550/NP241OR.

My first question is about the clocking angle issue. I'm trying to avoid this issue altogether if possible. From what I understand, the problem is the clocking is different between Wrangler NV3550's and other Jeep NV3550's. Is this true? So if I make 100% sure I'm getting a TJ transmission, I shouldn't have any clocking issues with the NP241 correct? I will also be doing a 1" body lift, so this might negate the clocking issue anyways.

My next question is about the clutch setup, you switched your plans so many times I lost track of what the final plan was. Will this setup work?

- Dakota Bellhousing 96-98
- Centerforce Clutch
- Advance Adapters Pilot Bushing (p/n 716167)
- Stock YJ 2.5 Flywheel (resurfaced)
- Stock YJ AX-5 Pressure Plate
- Stock YJ AX-5 Throwout Bearing
- Stock YJ AX-5 Clutch Release Arm
- Pre-Bled YJ AX-5 Clutch Master/Slave Combo (External Config)

And thanks for the great thread!
 
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