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· Jeep parking ONLY
1,535 Posts
Discussion Starter · #1 ·
This article discribes how to replace the Peugeot BA10/5 five speed transmission with the NV3550 five speed in a 1988 Jeep YJ.

Legal disclamer:
These are not instructions!
Always work safely and under supervision.
Do not attempt the following at all unless you are qualified!
I do not accept any responsibility for your actions based on this article.
By reading further you release me and this site from any responsibility and further indemnify me from any financial remuneration, legal procedings or otherwise.

Best Viewed In 1600x1200 mode.

Vehicle Background:
What we have here is an 88 YJ (see sig below). I DESTROYED reverse gear without too much effort and in short order (1st is complaining too). I had budgeted replacing the tranny from the moment I purchased my heap.

Rebuild Options/Goals:
My goal with this swap is simple...Get back on the road with a NEW transmission (not rebuilt or yard sourced) that will handle most anything I dish out, and not open a huge can of worms. So I did a mess of research on the NV3550 and NV4500.

Turns out th NV3550 fit the's how.

Rebuild Obsticals:
I faced some of the following problems.
  1. Budget
  2. Ease of swap
  3. Actual durability
  4. Future torque handling capacity
  5. Timeframe

We all know the prices so I wont bore you with that. Lets just say I cant afford to do this twice.

Ease of swap:
The AX-15 would probably have been just as easy to swap as the 3550 and I'm sure many people are very happy with the 15. I might have gone AX-15 but the ratios/torque capacity is better in the 3550. The 4500 is huge and awesome...but there's a bunch more fab work and drive shaft stuff that needs doing for that swap. Rebuild the 10/5? HA HA HAA!! It would be the easiest solution for sure...But I'm gonna use it as a garden planter, or for target practice...I haven't decided yet.

Actual Durability:
Considering my torque requirements (current and future) I have decided that I will never ever go above 300 lb/ft from the engine. Given that I will be using this jeep as a driver and mild crawler/tow vehicle, I won't be needing a "trail rated" granny low, or huge torque capacity. The NV3550 is rated 300 lb/ft (conservatively) based on a GVW of 7200 lb.
I think my jeep is about half that weight.

Future Torque Capacity:
If I am correct in assuming my injected 4.2 is producing about 207 ft/lbs at the crank (180x1.15), then it's safe to say I'm in the clear with the current motor. However, assuming the conservative rating of the 3550, if I do swap in a nice new 4.0 and stroke it with the old 4.2 internals, or go with a 3.8 S/C (who knows), I will still be safe.

I want a "drop-in" tranny upgrade!! Unfortunately those don't come easy. The idea of fabricating for weeks and trouble shooting after that, puts most "granny low" transmissions out of the picture for me. Time is not a huge factor for me, but I don't want to be on my back battling with mechanical jigsaw puzzles for months. The best solution is coming into focus...

Let the sparks fly!
So I ordered the NV3550 conversion kit available from High-Impact Transmission & Gear

Stage one - Teardown:

2 huge boxes arrived at my door after waiting patiently for my Sept. X-mas. The Tranny in one and the adapters/clutch in the other.

I took a quick inventory of all the stuff..."yup all there....woah....whats THAT?"....A chipped Clutch plate thats what.<Replaced Free of charge by Advance Adapters after some E-mailing and picture taking. (AA is a great company)


Started by removing the shifters.

Then the front and rear drive shafts came off.

The rear U-joints were in a bad state. One litterally fell apart right away, displaying the roller berings inside. The other was siezed.

Next I lowered the belly pan.

This is about the point when I broke out the ziplocks for labling and storage of "loose items".

Then I removed all the vac lines, speedo cable, backup light wires, vent tubes, and cobwebs and removed the x-fer case.


· Jeep parking ONLY
1,535 Posts
Discussion Starter · #3 ·
Installment #2 - NP231 Input Gear Replacement

First I cracked open the case...

Then Removed the mode and range forks...

(note the main-shaft synchro snap ring in the photo below)

off comes the main shaft, chain and front output shaft.

That leaves the main shaft and back half of the case...

After removing the planitary retainer on the transmission side of the front half, the planitary and input gear comes out as a unit...then remove the input gear retainer...(note there is no need to remove the large ring gear retainer inside the case)

Then note the position of the input gear thrust washers...

Now you can clearly see the two input gears side by side (new left, old right)...

Installation is the reverse of removal.

Then removing some more retainers...

Off comes the pump housing...


· Jeep parking ONLY
1,535 Posts
Discussion Starter · #5 ·
Installment #3

Here's the Transfer Case test fit to the NV3550

Relese arm and throwout bearing in place.


Advance Adapters shift braket with "Z" gate installed from old braket.

Here's a good example of a flywheel in need of resurfacing. It's glazed and scored pretty bad.

I pulled the pilot bearing with a $25 puller. Worked great and fast.

Dead pressure plate. *note the bluing and scoring

The old clutch plate is at about half wear.

And Finally the old TURD from two angles.

More to come.

· Jeep parking ONLY
1,535 Posts
Discussion Starter · #6 ·
Installment #4
It seems that the BA-10/5 has only 5 bolts holding the transfer case to the tranny. My transfer case had a nylon plug in the bottom right(viewed from t-case output) stud hole. I drilled out the nylon and chased the threads (which were intact) with a 3/8" corse tap.

I then mounted the transfer case to the tranny for the last friggin time. I used red thread locking compund on all this stuff. * note I replaced the studs with bolts. The bolts that go through the t-case bracket are longer due to 1/4" bracket thickness.

I soaked the pilot bushing overnight in motor oil, after measuring both the input shaft of the nv3550 and the crank to confirm the fitment:

I dressed the crank with 220 sandpaper to remove what little corrosion there was. I then began "pressing" the pilot in place:

I used a 1 1/4" socket and a regular hammer with some paper towel between the pilot and the socket. Hammered evenly around all edges of the pilot until seated.

I then removed each flywheel bolt one by one and applyed red thread locking compund before torquing them to 40 lb/ft. I then used the impact wrench to "degree" the bolts an additional 60° (from 12 to 2 o'clock).

Next I put the stubby end of the clutch alignment tool into the pilot and slid the clutch plate over the tool.

I applied the alignment cone to the tool and centered the clutch plate.


· Jeep parking ONLY
1,535 Posts
Discussion Starter · #7 ·
Installment #4 continued:

Next came the pressure plate. I applied red locking compund, hand tightened each bolt and centered the plate the best I could.

I then torqued the plate bolts to spec. 40-45lb/ft with my cheap flex beam wrench.

Back to the tranny/x-fer case - I put a new output yoke seal in the x-fer case and for good measure I applied some RTV. I then torqued the output yoke nut to spec. (170lb/ft) with an old tire iron wedged between the yoke and the floor to hold everything from spinning:

Then I took a break from that and decided to bleed the clutch slave/master and install the new lines. I had to remove the support rod from it's mount in order to get the master cap off.

I installed the 40" and 12" extension braided stainless line at the master: (EDIT You will see that the 90° elbow is on the master side in this photo. This turned out to be wrong, and I reversed the line to mount the elbow at the slave (clearance issue)

...and bled the slave by removing the plastic straps holding the slave piston in, filling the slave with fresh fluid, pumping the master while keeping it topped, installing the line at the slave once there was fluid in the line, and (holding the slave low to the ground and vertical) pumping the slave over and over and......until there were no more air bubbles reaching the master.

Then it was time to go under...In order
to slide the tranny under I had to remove the shift tower.

I had to give in and impact-wrench the exhaust off to get the tranny up and on.

And thats where it's at....I am having some trouble guiding her home.
So I went out and bought a trans jack adaptor for my floor jack.

· Jeep parking ONLY
1,535 Posts
Discussion Starter · #8 ·
Installment #5

In no uncertain terms, reinstalling the transmission is the biggest PITA of this whole build. I cannot stress enough how important it is to align the clutch perfectly. If you don't you'll be wrestling with the trans for hours (like I did) and you won't get anywhere.

The trans adaptor for the floor jack made all the difference too.

I dropped the trans one last time to double check the clutch alignment. Big supprise, it was off center by about 1/16". Here's where I stress again that you must double and triple check the alignment of the clutch.

So after realigning, I jacked up the tranny again and played with it for about an hour to get it home. There's NOTHING more satisfiying than seeing that pig slide home.

I used the two side bolts and one of the top bolts to align and drive the trans the last 1/2".

When you are doing any work which involves removing the tranny, make sure when you put it back on, the splines of the input shaft and the clutch are aligned.

I then continued by removing some dead u-joints:

More to come in the next installment!

· Jeep parking ONLY
1,535 Posts
Discussion Starter · #9 ·
Ok so Ive been driving with the new trans for a while now...overall I am satisfied.
Offroad the lower first gear is great.
Shifting could be better but I have some ideas about that which I will be working on soon.

Total Cost Involved (CDN dollars):
Tools $300
Oils $100
Tranny kit $2800
fasteners & misc $50
Shipping tax & duties $195
Total: $3445

Total time down 3 weeks.
Total time worked: 35 hrs
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