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banjodog 02-04-2010 04:01 AM

6 speed hard to shift with redline
hey guys, i got a 6 speed 05 tj and i put redline mtl in it a few thousand km ago, now when the transmission heats up to operating temp, shifting down from 6th to 5th feels very weird, it feels like there is sand or something in the gear lever (not very smooth shifting in 5th and 6th but not grinding.) please help guys, what should i check?

rrich 02-04-2010 04:51 AM

Get rid of the Redline backyard brew, put in the oil the mfgr says to use (the Service Manual, the dealer's computer etc.)

If anybody would know what it's designed to use, the makers of the transmission would know.

You may have to flush the Redcrap out first.

There are lots of "backyard brews" around. Just ask to see the Redline or whoever's refinery.

usaftj05 02-04-2010 09:24 AM

I use royal purple in my 05 tj 6 speed. It fixed all of my shifting problems and it shifts very smoothly in the cold weather.

bigskydrift 02-04-2010 09:33 AM


Originally Posted by rrich (Post 538227)
Get rid of the Redline backyard brew, put in the oil the mfgr says to use (the Service Manual, the dealer's computer etc.)

If anybody would know what it's designed to use, the makers of the transmission would know.

You may have to flush the Redcrap out first.

There are lots of "backyard brews" around. Just ask to see the Redline or whoever's refinery.

Red Line is a high-end lube, I have had excellent luck with Red Line, read this article, especially the part that pertains to the synchros in your trany.....although this pertains to the AX-5 & 15 trany's.......not sure about the 6 speed?
Jeep Articles / General (Red Line Oil MT90) - MoabJeeper Magazine

Schmo 02-04-2010 10:19 AM

I was concerned about getting the right fluid in my 6 speed tranny when I flushed it a few weeks ago . . . did a lot of searching to try to find a good quality oil that would meet the factory requirements . . . at the end of the day, I ended up going with the Mopar Stuff from the dealership . . . 20 bucks a bottle, but only took two . . . so I just felt safer going with the stuff that was already in there and it's working fine. Seeing that it'll cost you less to just flush it out than it would be to even have it diagnosed, that would be my suggestion. Not sure if you need to really flush out the old . . . being a bit anal, I would probably pick up an extra bottle, drain the tranny of the Redline, put the plug on and squirt in the extra new bottle, drain it again, just to get as much leftover Redline out of there and then would refill it.

pokey 02-04-2010 11:23 AM

I put redline in my '99 sport and it works great and is highly recommended for the ax15, however I'm not sure about the 6 speed.

rrich 02-04-2010 11:53 AM

It seems like some of those "backyard brews" work OK at first. But after a few miles, maybe a few hundred, they start giving shifting troubles.
Could it be the additives they put in evaporate or change chemically?

Maybe it's the ink or food coloring in them goes bad?

The guys that designed the transmissions - were they split personalities? How could they design a transmission that works great, then not be smart enough to select the lubricant it needs? Think about it - are they really just 1/2 crazy? Which half?

How is it that an armchair racer can read misleading advertising and his word is now taken for fact? Must be human nature to not believe common sense.

Why would Chrysler, or any OEM, go to all the expense and trouble to formulate their own lubes if better ones are already available? Wouldn't you think they'd just re-brand them or buy out the company and patents?

It amazes me that anybody still uses the wrong stuff, them complains that it doesn't shift right.

Sometimes just changing out the backyard brew and refilling with the proper stuff is enough. Sometimes enough of the old stuff stays in it to still cause troubles.

Flush - drain the old stuff out - let it drip awhile!
Refill about 1/2 way with kerosene - jack all the wheels up off the ground.
Start the engine in Neutral, then slowly shift it through all the gears - DO NOT SPEED UP THE ENGINE!

The purpose is to get the kerosene to wash all internal parts and dissolve all the backyard stuff.
Drain, let it drip, refill with the correct fluid.
Any leftover kerosene will evaporate once it gets warm.

REMEMBER -- paper and the internet do not reject words - false advertising doesn't dissolve. (Politicians take advantage of that!)

pokey 02-04-2010 12:02 PM

With all due respect RRich, redline mtl is a gl4 lubricant which is what the ax15 MUST have, not a gl5 which is all that is available now. Mopar discontinued the ax15 lube and they will sell you Mopar motor oil for the ax15 if you go to the dealer. Redline has a very good reputation. Now the newer 6 speed trannies probably need the gl5, however I'm not positive.

Jerry Bransford 02-04-2010 12:57 PM

No tranny would have a GL-5 spec, GL-5 is for the hypoid-cut gears inside the axles. Plus most GL-5 gear lubes, not all, have harsh sulphur-based additives that are hard on the synchros. Some GL-5 gear lubes like from Royal Purple & Amsoil are fine for use in transmissions, they don't use sulphur-based additives to achieve the GL-5 spec as most others do.

I'm a fan of Redline MT-90 for the AX-15 and AX-5, it's a superb quality fully synthetic GL-4 gear lube that is ideal for those transmissions. I'm no so sure it's the right stuff for the NV3550 or NSG370 so far as specs go but it wouldn't cause that grinding issue.

Where lubes go, Jeep doesn't make their own lubes & they use lubes that are available on the open market without having to buy them from the dealership. I do know that Royal Purple and Amsoil make lubes that are well suited to the NSG370 (& NV3550) but to verify if MTL is ok to use in the NSG370 or NV3550, I'd call Redline for confirmation.

The stuff the dealership sells at wildly inflated prices aren't going to give you any benefit over an aftermarket gear lube that is of good quality and meets the specifications. And Jeep will warranty the transmission with RP in it just like they would if it was filled with something that Chrysler is buying from one of the major lubricant producers and putting their name on. I personally think you can easily find BETTER lubricants than what the factory uses because they're not willing to pay a nickle more than they have to for such things.

Jerry Bransford 02-04-2010 01:25 PM


Originally Posted by pokey (Post 538422)
I put redline in my '99 sport and it works great and is highly recommended for the ax15, however I'm not sure about the 6 speed.

Hey I know you, it's been years! How the heck have you been Bud?

pokey 02-04-2010 02:53 PM

Hey Jerry, I've been lurking on this site for awhile and I'm a geezer like you, live in SoCal, but don't know we have ever met. The sport is my third Jeep. Had a '75 CJ5 and an '81 Scrambler.

Jerry Bransford 02-04-2010 03:02 PM

Yep we met, it was at your house years (probably 10) ago plus once more when a bunch of Jeepers got together over on Mission Bay. I forget why I was there but you were helping to install a front lunchbox locker while I was there for some other reason. Oh I remember now, I bought a front bumper & picked it up from your house. We installed it while I was there.

Jerry Bransford 02-04-2010 05:01 PM

Mistaken identity on my part, Pokey is a different Pokey from who I know. :)

Schmo 02-04-2010 05:10 PM

Were you thinking of this Pokey?

pokey 02-04-2010 05:26 PM

No he wasn't. Thats a picture of me.

rrich 02-04-2010 05:34 PM

Obviously Chrysler isn't in the business of making their own oils. They buy from people that do. Mobil Oil doesn't make transmission or engines either.

But - like gasoline - each individual company adds there own "secret" additives. That's why you can see a Union Oil gas truck filling up at a Mobil refinery. They simply dump in the additives Union wants.

Redline, Purple, Bubba and Yahoo's oils are the same way. The difference is the additives - and the packaging. And of course the hype.

Are all steaks the same at restaurants? Why then are some more tender, some taste better, and some can even be terrible? Storage, preparation, and seasoning (additives) make a big difference.

Ha Ha - Are all women the same? The basic specs can be the same GL-3, GL-4, GL-200, 35-23-35 etc. but there sure is a difference! (Ha Ha - it took me several wives and girlfriends to find that out!!! But it was fun doing the research.)

Specs are all rated at new unused oil. But what happens after 200 miles? 10,000 miles? 100,000 miles? (Or 10 years of marriage?)

It's been my experience - owning 3 different auto repair shops and now a "once in a while retired shop" that using many of the fad oils can cause problems. I've personally witnessed dozens or more of seeing the wrong oils used with synchros that caused trouble - hard shifting - hard to get in gear and even hard to get it out of gear, grinding, noises, etc.

A simple dump, or dump and flush, then replace with the OEM recommended oil has often fixed it. It's far cheaper and easier than R&Ring a transmission just to clean the synchros. In my opinion, it's step 1. (Ever spend an hour or so trying to brush the teflon or graphite rubble from synchro splines?)

You see on cans of stuff in the parts houses - "add to manual transmissions" - Slick 50, ST, Marvel, Lucas. The teflon or graphite type additives are included.
Most promise less heat, better shifting, better mileage. They all may be better for the bearings - but they all change or destroy the ability of the synchros to speed up the gears properly - remember - synchros are a friction device! So are clutches and brakes!

I personally witnessed a guy that I'd just rebuilt his 3 speed T-14. It was working great. He went home and put Slick 50 in it - he said he didn't use very much. You could not get it in gear from Neutral when the engine was running. It didn't take much of that slick stuff to kill the cone friction!

He brought it back on a tow truck - wanted me to warranty it. I wouldn't, but I made him a bet - I'd take it apart and fix it if it was a mechanical problem, otherwise he pays me to drain and flush - I think it took 3 flushes to get all that slippery out - then it finally worked fine. That T-14 was designed to use plain old 90 wt. He paid.

The clue about it feeling gritty when shifting - I don't recall what caused it, but it was one of the "magic oils." The oil itself didn't feel gritty, but when shifting it tended to make little balls or globs on the splines which made it feel like it had sand in it.

You can take your chance and try things that weren't designed to be used in it - they may work they may not.

It's like saying using plugs in your 4.0 from from a Chrysler 400 or PT Cruiser are better than what's called for in the service manual and under hood label.

It may work, but at what price?

Sorry, I can only advise, based on my experiences.

Hensman 02-04-2010 06:47 PM

All i know is that I first changed out the fluid in my six speed at 60k and put in royal purple and it didn't help my grinding at all. I then put mopar fluid in and it helped, but it stills grinds, but just not as much. I took it into the dealer today and I guess I'll see what they say. Hopefully its covered under my warranty.

mccgsm 03-24-2013 10:42 PM

I had a slightly different problem, but the primary symptom was increasingly difficult shifting into 5th and 6th. Pulled the upper boot; the inner rubber boot was torn so I was able to see the rubber seal at the top of the shift lever tower--it's a grooved, circular seal and there was quite a bit of sandy crud in the grooves from going through puddles around the Phoenix area which has a lot of "decomposed granite" soils. Blew the crud out and it eliminated the stiff shifting--basically the grooves on the left side of the seal were packed with fine grit which prevented the accordion pleates from compressing easily when the gearshift was moved to the right. Hmmm. That said, I have the usual noisy synchros and mildly sticky shifts at temperature extremes. I put in Royal Purple synchromesh synthetic rather than Pennzoil standard synchromesh fluid and it does shift more smoothly--no report yet on synchros as I've not run it hot and hard yet.....

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