Forums
New posts
Search forums
Image search
Shop
Amazon Store
T-Shirts
Stickers
Members
Current visitors
Supporting Member Upgrade
Sponsors
About
Log in
Register
Search
Search titles only
By:
Search titles only
By:
New posts
Search forums
Image search
Search
Search titles only
By:
Search titles only
By:
Menu
Install the app
Install
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Forums
Jeep Wrangler YJ
YJ General Discussion
Improving synchro shifting problems by using different gear lube weights or additives?
Reply to thread
Message
<blockquote data-quote="machoheadgames" data-source="post: 429447" data-attributes="member: 18789"><p>You would be perfectly fine with 75W90 GL4. That is the official spec from Aisin Warner, the transmission manufacturer, and it has always worked perfectly for me. Chrysler wrote the owner's manual incorrectly and told people to use 75W90 GL5. After Chrysler realized their mistake, they put out a technical service bulletin to dealers to fill the transmissions with 10W30 motor oil because 75W90 GL4 is rather rare and not something dealers normally keep in stock (and probably not a fluid that Mopar even makes, which is what they use for virtually all fluid changes). 10W30 engine oil and 75W90 gear oil are almost the same viscosity, because they are measured on different scales. The difference really comes down to the additive package, and the fluids like MT90 are made for transmissions, and 10W30 are made for engines.....one might not contain the ideal additive package for the other. Engine oil likely doesn't have as good of an additive package for a transmission as GL4 transmission fluid itself would. No way to truly confirm that, but I'm going to rely on the transmission manufacturer's recommendation, not Chrysler or internet folk. Chrysler messed it all up to begin with anyways, so why would I trust their advice anyways? I at least wouldn't choose to listen to them when the transmission builder advises differently.</p><p></p><p>GL5 definitely did not shift well in my transmission. Not sure what weight it was because it was in there before I bought the Jeep, but it was definitely some form of GL5 due to the smell. GL4 is what is officially called for by the transmission manufacturer, I still don't understand why people try to dwindle from it. I have had a decent amount of below freezing days over the years and it always shifted perfectly. I have also never seen somebody else install MT90 and have bad results from it, it's always been an improvement.</p><p></p><p>Virtually all shifting issues I've seen people have stem from running GL5, synchro damage from long term use of GL5, and stiff old shifter boots. New rubber boots are nice and soft, and work well. Leather boots are a good option too.</p></blockquote><p></p>
[QUOTE="machoheadgames, post: 429447, member: 18789"] You would be perfectly fine with 75W90 GL4. That is the official spec from Aisin Warner, the transmission manufacturer, and it has always worked perfectly for me. Chrysler wrote the owner's manual incorrectly and told people to use 75W90 GL5. After Chrysler realized their mistake, they put out a technical service bulletin to dealers to fill the transmissions with 10W30 motor oil because 75W90 GL4 is rather rare and not something dealers normally keep in stock (and probably not a fluid that Mopar even makes, which is what they use for virtually all fluid changes). 10W30 engine oil and 75W90 gear oil are almost the same viscosity, because they are measured on different scales. The difference really comes down to the additive package, and the fluids like MT90 are made for transmissions, and 10W30 are made for engines.....one might not contain the ideal additive package for the other. Engine oil likely doesn't have as good of an additive package for a transmission as GL4 transmission fluid itself would. No way to truly confirm that, but I'm going to rely on the transmission manufacturer's recommendation, not Chrysler or internet folk. Chrysler messed it all up to begin with anyways, so why would I trust their advice anyways? I at least wouldn't choose to listen to them when the transmission builder advises differently. GL5 definitely did not shift well in my transmission. Not sure what weight it was because it was in there before I bought the Jeep, but it was definitely some form of GL5 due to the smell. GL4 is what is officially called for by the transmission manufacturer, I still don't understand why people try to dwindle from it. I have had a decent amount of below freezing days over the years and it always shifted perfectly. I have also never seen somebody else install MT90 and have bad results from it, it's always been an improvement. Virtually all shifting issues I've seen people have stem from running GL5, synchro damage from long term use of GL5, and stiff old shifter boots. New rubber boots are nice and soft, and work well. Leather boots are a good option too. [/QUOTE]
Verification
Post reply
Forums
Jeep Wrangler YJ
YJ General Discussion
Improving synchro shifting problems by using different gear lube weights or additives?
Top
Bottom