Transmission syncros grind when cold

[Jerry Bransford]

X2 to this, solid advice.

You can get a brand new AX-15 from Advanced Adapters for $1574:
https://www.advanceadapters.com/products/26-ax15--aisin-ax15-5-speed-transmission-new/

The NV3550 can be had, but it's usually around $2500 for a new one.

Between those two transmissions I'd go for the stronger AX-15 every time.

 

[2006 Wrangler LJ Rubicon]

Jerry what do they reccomend for the nsg370 (6speed)?

I have the NSG370 in a 2006 LJ, and in a 2007 Liberty. The Red Line previously mentioned seems to be popular online. I use the Pennzoil Synchomesh fluid, and they both shift great. The key spec to look out for is Chrysler MS-9224. There is also one from Valvoline, I have not tried it yet.

https://en.wikipedia.org/wiki/Chrysler_NSG370_transmission

https://www.amazon.com/dp/B0002KL098/?tag=wranglerorg-20

https://www.amazon.com/dp/B071YBH8P1/?tag=wranglerorg-20

 

[Jerry Bransford]

I have the NSG370 in a 2006 LJ, and in a 2007 Liberty. The Red Line previously mentioned seems to be popular online. I use the Pennzoil Synchomesh fluid, and they both shift great

Not many think GM or Pennzoil Synchromesh is a good choice, there are a lot of complaints about what it does to shifting quality once it has been in there a while. Pennzoil/GM Synchromesh is also a conventional gear lube, not a synthetic, and that is another strike against it for extreme cold weather use. Synthetic gear lubes in transmissions help them shift more easily since synthetic gear lubes flow better in cold conditions.

I'm not a fanboy of synthetic lubes, I run strictly conventional gear lubes in my axles and engine oils, but synthetic gear lubes are clearly the way to go for our transmissions. ESPECIALLY in cold conditions like the OP is complaining about. My recommendation to the OP for his cold weather shifting problems is to try changing to Redline MTL which is a full synthetic that meets all the specs for his transmission. It's not a miracle-worker by any means but for cold weather shifting issues it'd be my first thing to do.

 

[2006 Wrangler LJ Rubicon]

Well, I wouldn't say "not many" think it is a good choice. It is well reviewed elsewhere, or I would not have tried it. I will get back to you in two or three years to see if things get any worse.

 

[Airjunky]

The trans in my 02 grinds going into 2nd if I try to shift too quickly. I drained it & filled it with the RedLine MTL, which did make a bit of an improvement. If I slow the shift down a bit, it's fine. But if I'm climbing a hill, grabbin gears, it always grinds going into 2nd.