# Synthetic GL-4 in 5-speed?



## isb360 (Apr 6, 2005)

The rubber boot that goes between the shift linkage and the transmission selector input is broken. I noticed it while changing the oil the other day. The good news is that new boots are available from Nissan for under $9...not bad.

The torn boot has allowed fluid to ooze out over time -- quantity unknown. I am going to take the opportunity while changing boot to change the fluid in the 5-speed. 

I see that GL-4 (presumably 75W-90 weight) is recommended. That's ok. *What I am wondering is would there be any downsides to switching to a synthetic (Amsoil, etc) GL-4 lubricant?* Will it affect synchronizer meshing? Tranny has 213k miles on it and shifting to 2nd is a bit balky. Who knows if that is the result of sticky linkage, lots of use and wear, or lack of lubricant, or combination of the above.

I switched to Amsoil in my Ram diesel truck and it shifted smoother and with less resistance, especially in colder weather.

Thoughts/suggestions?

Thanks
Tim


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## Bror Jace (Apr 26, 2003)

_" ... would there be any downsides to switching to a synthetic (Amsoil, etc) GL-4 lubricant?[/B] Will it affect synchronizer meshing?"_

Nope. I'd switch in half a heartbeat. :thumbup: 

A GL-4 syncromesh fluid is the _ideal_ fluid to use in any synchronized transmission. Any good fluid (including synthetics) will be friction modified for best synchro engagement. Don't assume that just because it says "synthetic" it will be more slippery. That is not necessarily true.

The only thing you want to be extra careful of is matching the weight. Don't deviate from the recommended weight without a _really good_ reason and that would probably mean you either live in Death Valley ... or north of the Arctic Circle. 

In a 75W-90 GL-4, I like Specialty Formulations MTL-R the best with Red Line MT-90 a second choice. I understand Amsoil has finally come out with some syncromesh fluids and they'd be my third choice.

Don't use a fluid unless you can confirm its weight.

I assume your 2nd gear issue is the result of wear. A fluid change _may_ help this ... but I wouldn't bet a lot of money on it.

More reading for you:

http://www.nissanforums.com/showthread.php?t=108271&page=1&highlight=syncromesh 

http://www.nissanforums.com/showthread.php?t=110539&highlight=syncromesh

http://www.nissanforums.com/showthread.php?t=106646&page=1&highlight=syncromesh

http://www.nissanforums.com/showthread.php?t=104196&highlight=syncromesh

http://www.nissanforums.com/showthread.php?t=90795&page=1&highlight=syncromesh

http://www.nissanforums.com/showthread.php?t=100116&highlight=syncromesh

http://www.nissanforums.com/showthread.php?t=86620&page=1&highlight=syncromesh


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## isb360 (Apr 6, 2005)

Ok, here's what happened. I got 3qt Amsoil 75W-90 (GL-4 equivalent), got under the car, changed the shift linkage boot, and then was unable to remove the countersunk flat-screwdriver bolt that serves as the drain for the tranny (I was starting to strip it). The two bolts adjacent to the "drain plug" looked like they went into the tranny cavity, and thus I reasoned if I removed one or both of them, the fluid in the tranny would drain. This has been my experience with other vehicles.

So,,,,I pulled out the two bolts, they were wet and smelled of gear lube, but nothing drained out. Yikes, the transmission was empty!..or so I thought. That explains balky 2nd gear shift...or so I thought.

I took out the fill plug, inserted an extension funnel, and because I couldn't clearly see the fill hole while adding, I even put my oil drain pan under the car with some clean paper towels in it, that way when it was full and "dribbling out" of the fill hole, I would be alerted.

Two thirds of my way through pouring the second quart, I hear a dribbling noise. I stop and look under the car and what do I see? The majority of all the fluid I had just poured was running out the fill hole, down the bottom of the curved bellhousing (thus missing the drain pan entirely), and making a nice sized puddle on the driveway.

I guess there was fluid in it after all! But by the streaky mix of fluids I observed on the driveway, at least some good came of the debacle...some new fluid flushed out some of the old fluid. 

Still shifts the same as it did before, maybe a bit better. Good enough for winter. Will tackle it again in the spring.

Tim


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