Can Using a Thicker Viscosity Tranny Fluid On An ATF+4 spec'd Manual Cause Problems ?

[Idrinkmotoroil]

I've got a 5 speed tranny which calls for ATF+4 fluid on my 04 Dodge with Quaife Limited Slip Diff. The ATF+4 fluid worked terrible from day one (they also recommend 4 oz of Mopar Friction Modifier to be used with the ATF+4).

I started running Redline's C+ATF and Mopar FM a few months ago and it worked a good deal better than the stock fluid. However as soon as the hot weather hit these parts last week the tranny began shifting noticeably worse with about 5000 miles on the C+ATF. I tried running GM Synchromesh with Mopar FM but I was getting a shuddering feeling in tight low speed turning so I dumped it after 2 days, but the tranny shifted very well with it. I have now switched to Redline MTL (with no Mopar FM) and the shifting is fantastic in hot weather, and there is no shuddering under tight cornering from the LSD/diff.

Redline MTL is a good bit thicker than ATF+4 or C+ATF. My thinking is that a thicker fluid cant be worse for wear on the gears or LSD, and if it promotes smooth shifts then it should be working well with the synchros. It likely wont work as well in cold temps but I dont really drive it much in winter. Any cautions about using this fluid in an ATF spec'd tranny ?, I'm loving it but I'd appreciate any advice. I chatted with Dave over at Redline and he seems to think its a good move. Any other opinions welcomed. thanks !

Sorry to keep chatting about this issue and my vehicle/tranny but I've been experimenting quite a bit with this stuff.

regards,
Joey

 

[MolaKule]

Is this a transaxle with the Quaife LS in the transaxle?

 

[Idrinkmotoroil]

quote:

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Originally posted by MolaKule:
Is this a transaxle with the Quaife LS in the transaxle?

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yes a fwd, tranny and diff combined with one fluid. It makes no sense to me why the diff was shuddering/vibrting with the GM Sychromesh as the Quaife is a clutchless gear driven unit. Nonetheless it has disappeared with the Redline MTL in there , and no Mopar FM added either.

Joey

 

[MolaKule]

The GM synchromesh is a 9.5 cSt oil whereas the MTL is about a 11.5 cSt oil.

The MTL has a higher level of AW adds as well, so I would think it should offer better protection.

I have no idea where the shudder originated if indeed it was shudder.

 

[Idrinkmotoroil]

thanks for the reply Molakule, makes sense to me to have a bit more viscosity. Just want to make sure that I wasnt missing something about ATF+4 which makes it important to use.

 

[Idrinkmotoroil]

Just as an update, I've been running Redline MTL for a few more days and this stuff just transformed the shifting on my tranny from rough to buttery smooth. This has been a huge improvement, I'm extremely surprised that a fluid could make such a differnce. Loving the way this stuff works , Redline make some seriously good fluids. Hats off to them, and their customer support from Dave G. is worth every penny. Thanks for the replies here on this forum as well.

Joey