Amsoil Differential and Transmission Oils Review

[radroach]

@Spuds

Great review, I might have to try amsoil on my next MT fill (probably a couple years down the road. I am however concerned about your statements about what's going on in the differential, not sure if there's any real basis or fact in what you're saying about the different behavior so I'll have to take that with a grain of salt.

@venturaII indeed there is some concern about using a GL5 oil in the transmission, but I've read many times that Motul Gear 300 uses additives that reduce the negative effects on yellow metals. I've been using Motul for the last 3 years, had about 3-4 changes of it in the last 60,000 miles and it's been ok. The serviceable life of it for me is about 15,000 miles though and it does seem to degrade after that.

[venturaII]

Originally Posted by radroach

@venturaII indeed there is some concern about using a GL5 oil in the transmission, but I've read many times that Motul Gear 300 uses additives that reduce the negative effects on yellow metals. I've been using Motul for the last 3 years, had about 3-4 changes of it in the last 60,000 miles and it's been ok. The serviceable life of it for me is about 15,000 miles though and it does seem to degrade after that.

Those buffers work as a coating on the yellow metals to protect them from the corrosive action of the GL5 additives. However the coating will flake off the surface of the brass syncros every time they are engaged, which has a double negative impact of not only re-exposing the syncros to the corrosive ingredients, but also additionally by actually removing some of the substrate material itself (the brass) when the coating comes off. Differentials don't have this sort of inherent action, but synchronized transmissions do. Non-synchronized transmissions are another story entirely.

I suggest having an oil analysis done of your used GL5 transmission oil; I'll bet the yellow metal content will be high.

[Spuds]

Originally Posted by radroach

@Spuds

Great review, I might have to try amsoil on my next MT fill (probably a couple years down the road. I am however concerned about your statements about what's going on in the differential, not sure if there's any real basis or fact in what you're saying about the different behavior so I'll have to take that with a grain of salt.

Thanks! As far as the diff, the worm gears will bind under certain torque conditions with little regard as to what lubricant is put in. I believe the friction modifier spreads that threshold out by creating a bit more resistance under load (meaning when there is a torque difference between wheels). The mechanical binding would still occur at approximately the same point, but the viscous forces would resist the torque difference between the wheels at a lower level of difference. This would explain what I am feeling in my subjective review.

One of my hypotheses in this little experiment was that friction modifier was not going to have any effect which is why I didn't buy any to begin with. I still have to see what adding some does to prove that right or wrong, but current observations seem to suggest that hypothesis was incorrect.

[venturaII]

Originally Posted by venturaII

I'll be interested to hear your comments about the Amsoil trans fluid in the winter. So far I've only used Toyota LV 75W (~50K miles), but if the Amsoil works in cold weather, it might be a candidate going forward.

Well, just to add on to this thread, I just did another transmission lube change at ~54K miles. First was at 10K with warranty work; wrong lube was initially used and then dumped and replaced with the correct Toyota LV 75W fluid. Second change was by me at ~25K with the same Toyota fluid. This weekend I used Amsoil 75W-90 GL4 lube, and frankly, I don't like it. Noticeably notchier shifting, harder to get into first, even with double clutching on a slow roll. The transmission IS much quieter at idle in neutral though, which is interesting...

I'll probably give it 1000 miles; if things haven't improved, I'm dumping it and going back to the Toyota fluid, price be damned.

[Spuds]

Originally Posted by venturaII

Well, just to add on to this thread, I just did another transmission lube change at ~54K miles. First was at 10K with warranty work; wrong lube was initially used and then dumped and replaced with the correct Toyota LV 75W fluid. Second change was by me at ~25K with the same Toyota fluid. This weekend I used Amsoil 75W-90 GL4 lube, and frankly, I don't like it. Noticeably notchier shifting, harder to get into first, even with double clutching on a slow roll. The transmission IS much quieter at idle in neutral though, which is interesting...

I'll probably give it 1000 miles; if things haven't improved, I'm dumping it and going back to the Toyota fluid, price be damned.

Any mount/shifter modifications? What is your local temperature? Mines still been good all summer, but maybe I'll run into notchy-ness too as things cool down? Trying to figure out how we had opposite experiences.

Less sound would indicate to me less energy loss, and therefore typically better lubrication. However, that might make the synchros slower to react leading to more notchy feeling. .

[venturaII]

It's been around 60 degrees for the past week or so here in central New England. Shifter/transmission are 100% OEM, other than an aftermarket knob which has been on for ~6 months or so. The quieter operation I'm attributing to the slightly heavier 75W-90 Amsoil, versus the straight 75W Toyota fluid, though I could be wrong with that assumption. Might take a few hundred miles to break in to the different lube, so I'll be patient.. If the Amsoil is more 'slippery', that might account for the stiffer shifting/slower syncros, and maybe quieter running at the same time..?

[cueball89]

I have about 30k miles on amsoil manual transmission & transaxle gear lube. I can usually get a smooth first shift of the day 1>2 if I shift at 3000 rpm. I don't drive the car in the winter but I usually get some temperatures in the low 40's before I put the car away. I think I do recall more effort going into first gear but I don't have any issues double clutching in the rare autox hairpin. I only seem to experience crunchy shifting if I'm short-shifting the car, less than 3000 rpm, or shifting slowly like in traffic. Otherwise it's fairly smooth.

[venturaII]

Originally Posted by cueball89

I have about 30k miles on amsoil manual transmission & transaxle gear lube. I can usually get a smooth first shift of the day 1>2 if I shift at 3000 rpm. I don't drive the car in the winter but I usually get some temperatures in the low 40's before I put the car away. I think I do recall more effort going into first gear but I don't have any issues double clutching in the rare autox hairpin. I only seem to experience crunchy shifting if I'm short-shifting the car, less than 3000 rpm, or shifting slowly like in traffic. Otherwise it's fairly smooth.

I've noticed the same behavior when shortshifting 1-2 in cold weather, which seems like a natural thing to do until the motor warms up more. But holding 1st gear just a little bit longer before shifting does seem to help with the upshift, regardless of which fluid I've used.

I tend to be pretty easy on gearboxes and don't like a lot of effort required unless I know it's a beefy transmission, which ours has the reputation of NOT being.

[cueball89]

Originally Posted by venturaII

I tend to be pretty easy on gearboxes and don't like a lot of effort required unless I know it's a beefy transmission, which ours has the reputation of NOT being.

There's definitely more resistance going 2>1 in normal driving then heel toeing into 2>1 at 5000 rpm during an autox.

I put 260k miles on a 2003 wrx 5 speed transmission, the last 90k miles were with an 18G and heavy duty clutch. I don't think these transmissions have the same glass transmission reputation?

[Spuds]

Originally Posted by venturaII

I tend to be pretty easy on gearboxes and don't like a lot of effort required unless I know it's a beefy transmission, which ours has the reputation of NOT being.

I haven't heard about any reliability problems with 1-3 under any conditions. Usually the issues are with 4th right?

[venturaII]

Originally Posted by Spuds

I haven't heard about any reliability problems with 1-3 under any conditions. Usually the issues are with 4th right?

I got the impression our shift forks were also made of warm butter...maybe I'm wrong about that, but I consider the resistance to be excessive, especially compared to prior to the fluid swap.

[cueball89]

37F on the car thermometer this morning, smooth 1-2 shifts this morning.

[venturaII]

Originally Posted by cueball89

37F on the car thermometer this morning, smooth 1-2 shifts this morning.

Huh. It was ~32 here, and it was like shifting a box of Wheaties...

[Spuds]

Bump. Added an update to the first post.

@, Amsoil transmission oil has been great for me this winter. Just did a cold start around freezing yesterday and it was fine. You had asked in the second post.