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BlueFlu

Jeep YJ Wrangler AX5 Replacement Options

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Been reading a bit and lurking decided to join. 

Anyway I have a '94 YJ w/2.5 ax5 with ~105k.  I've done the 8.8 swap and many other upgrades to it. 

The ax5 is starting to grind 1st to 2nd and then downshifting to 2nd and 1st.  I will do a fluid swap and see if that calms it down.

However I'm thinking that it may be time for a tranny swap/upgrade.

The SM420/SM465 swaps seems to be the way to go for off road use but have yet to talk to anyone who has done it. Are they happy with the swap etc.

My other option is a Mopar 360 swap.  I have the engine and a NP435 sitting but can't find a t case adapter to keep the driver side drop. I thought at one time there was a flip kit for the D300 but couldn't even find that today.  

 

Any help? 

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BlueFlu, thanks for joining, we're glad to have you on board here!  The AX5 generally lasts more than 105K miles, though four-wheeling can retire any transmission earlier...

 

If you're remotely contemplating an end to 2.5L power, the 360 Mopar V-8 with an NP435 sounds intriguing.  I'm always surprised that the rugged Mopar pushrod LA engines get overlooked in favor of Ford or GM V-8s.  The AMC/Jeep inline six swap is just as complex as a V-8, since your four-cylinder frame requires relocation/reinstallation of engine frame mounts, which makes a 4.0L or 4.6L stroker swap as much work as a V-8 swap.  Not clear if you're dealing with emissions or if the 360 (5.9L) is '94 or newer.  What's this about?  The NP435 sounds like the carburetion era.

 

Otherwise, the SM420 or SM465 are each viable alternatives to the AX5.  The bellhousing could be an issue, however, and this is a conversation you'd need to have with Advance Adapters (1-800-350-2223, tech line).  The 2.5L four is a different bellhousing pattern than the 4.2L or 4.0L inline six, and there are no adapters available for the 2.5L.  I have some creative thoughts here, though, as the 2.5L may share a common bellhousing pattern with the 2.8L GM V-6 of old.  (If this rumor is true, it was an accommodation for the 1984-86 Jeep XJ Cherokee models that used the GM 2.8L V-6 option.)  If so, there may be a GM bellhousing that could serve as the missing link for an SM465 swap or possibly the SM420.  That's a whole other story that we can explore if you're pursuing that option. 

 

One shortfall of these bigger truck four-speeds would be the loss of an overdrive gear.  Unless you seldom need or use overdrive, this could be a hindrance...On the other hand, the non-synchromesh compound low gear of an SM420, SM465 or the NP435 is fantastic for rock crawling!

 

We can kick this around as much as you'd like, BlueFlu!

 

Moses

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Thanks for the welcome Moses.  

 

I think I used GL5 last time I changed the tranny fluid, I've read since of others having issues after using GL5.  Lesson learned I guess.  

 

The 2.8 GM v6 bell housing will work behind the 2.5 with a few minor mods.  I've seen a few 2.8 bell housings in pull a part type yards in S10s and even a few Cameros but have yet to pull one mainly due to not hearing much from the Jeep world on this one.  I do use my YJ on the street but mostly back roads and around home.  With a few 300 mile days a year tossed in for fun drives.  If we go to a trail ride any distance away I trailer it.  

 

I've always loved the small block Mopar mills, hard to beat them IMHO.  The 360 is '77 out of a Power Wagon but I plan to upgrade to fuel injection, like Holley or Eldebrock, and maybe add an air pump to help with emissions if I go the 360 route.  The '94 being OB1 they only do a sniff test here in TN.  They don't even ask about engine size or mods.

 

 I just can't bring myself to do a GM swap.   :D   

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The original Mopar gear oil should cross over to Valvoline's current MTF #811095 gear lube.  This emphasis on oil types in these Aisin transmissions has been largely exaggerated, BlueFlu.  I ran the official Mopar AX5/AX15 oil for years, until it was no longer available.  Toyota's equivalent transmissions use a recommended API GL4 or GL5 in 75W-90 or 80W-90 viscosity.  This readily available Valvoline oil should work well.  Redline and Amsoil offer alternative synthetics under these ratings.  What I would avoid is the "motor oil" equivalents suggested now by Mopar, as this is typically not an oil for gear mechanisms that require EP (Extreme Pressure) lubes.  That's my view...Here is Valvoline's viewpoint and part number cross-references:

 

Valvoline Transmission Lube Catalog.pdf

 

I can check the Mopar parts listings and my Mitchell Interchange Manual on the 2.8L GM V-6 and 2.5L AMC four if you need clarification.  Considering the "birth" of the 2.5L four at the same time AMC introduced the XJ Cherokee with its 2.8L GM V-6 option, a common bellhousing would have been consistent.  The AMC inline sixes shared bellhousing patterns with the AMC V-8s of their era.  It would, however, have been more helpful if AMC used the 4.0L/4.2L and V-8 bellhousing pattern across the board.  GM did this with small-block V-8s, post-"Stovebolt" inline sixes (194, 230, 250 and 292) and the 153 (Chevy II) four-cylinder.

 

Tennessee has a very realistic emissions strategy, Arizona once did this, too.  Tailpipe emissions are tailpipe emissions, and if the powertrain meets or exceeds the OEM engine emissions in good condition, that should be enough.  An EGR valve and air injection pump system would be helpful on that '77 engine.  Was this a catalytic converter chassis 360 V-8 model?  The Jeep will need a cat system to clean up downstream emissions.  From what you share, you can likely use a performance cat like Random Technologies.

 

Moses

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I did a fluid change yesterday and used the Valvoline MTF.  The tranny shifts smoother now but the grind is still there.  

 

 

From what I have read on Novak's site the 2.8 housing works with minor mods tranny dependent ie SM420 easier than the SM465 due to the mods needing to be done.  No big deal though.  Just a rib taken off and few a studs etc.  

 

I agree it would have been so much easier if Jeep had used a one size fit's all for the YJ in the frames and bell housings.  One of the things I always liked about the CJ's.  

 

 

I "think" the '77 had a cat but can't swear to it as we bought it as a basket/box case.  Was going to be a father son's project until my oldest son decided he likes the '96 XJ Country we have more.  LOL  So the PW is being parted out to fund upgrades on it and pick up another XJ for the other son because he likes the XJs too.. 

The YJ does have a high flow cat on it already with a 2.5" exhaust.    

 

Having sons who love Jeeps is a great problem to have.  :)

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