Power loss or gain depending on transmission fluid?

[Buffalobwana]

Before we took the Mission 22 truck on the 2000 mile trip from Idaho, through the mountains of Colorado, to Texas, I decided a full fluid and filter change was a wise idea. Based on numerous threads here, I used 15-40 for the transmission and engine. I was torn. Numerous threads, TM's, posts, opinions. What to use? Seems like anything including water will get you down the road. While water is a last resort.

When I first drove the truck after the fluid change, it seemed rather sluggish. Acceleration was slower than normal ... Or was I just imagining it?

Drove through all gears, checked level, a bit overfilled. Drained a bit, down to normal now, but I can't shake the feeling that its sluggish.

Make it all the way back to Texas. Shifted so smooth all the way. Ran cool even horsing it up over two 10k+' passes. (Grand Mesa and Monarch Pass).

So I hop in one of my other 923A2 here in TX, and it sure seems to accelerate faster.

Im not imagining it.

Anyone else see this happen with a fluid change? I'm thinking of doing a double flush and going to Dexron.

 

[Suprman]

Turn up the fuel rate slightly and then see how it drives.

 

[Buffalobwana]

Yep, I could, however, at the moment, I'm more interested in the physics behind this fluid change effect. I can go (back) to 10wt, 30wt or Dexron. But interested in hearing others opinion and experiences. See if anyone else has noticed a similar effect.

 

[WYomer]

Well hot its 15W and cold 20-30W in the summer (poophouse guess) its think and sluggish cold better hot....but still not 10WT. Save the 15-40 for the Middle East is my opinion.

If youve even torn into a torque converter or valve body you'd see why.

 

[Buffalobwana]

Never took on that challenge. Trying to avoid it if possible.

By the way I live in TX, while it isn't the Middle East, it's a hot sumbeech out there right now!

I was amazed at the noticable difference between the two fluids.

What "weight" would Dexron be equal to? 10wt/hydraulic fluid? Does thicker translate into more "bite" so to speak? Turning into more power transferred to the wheels?

Has as anyone else ever noticed this? Or are my truck whispering skills very finely tuned !!

 

[simp5782]

DexIII is equal to 10wt with additives. I have noticed no difference towing or empty since switching to DEXIII

 

[WYomer]

Yup Dex and Tractor oil are all 10WT. I dont think you'll get any power gains but you will get faster response with lighter fluid. Basically when looking at the valvle body the fluid runs in chambers that look like worm tunnels in wood. When the pressure peaks for that tunnel the pressure overcomes a spring that pops a ball bearing into place as a blockage. So once its blocked there is no difference, the only grip your going to get are clutches or bands that run around the shaft and grip for whatever gear the valve body wants you in. Once those bands start slipping your looking at a rebuild since they run out of material to grip. Heavier oil in hot climates might help lubricate and cool adding to extra life but thats also what friction modifiers do.

This is why I think using the TM for your climate for fluids is so critical. Here in the Rockies I'm using 10WT tractor oil and loving it, Texas I might go 15-40 for summer time if I was hauling. If I wasn't hauling I'd likely stay with 10WT

I got mine from Northern Montana in late winter full of 15-40 and until it was warmed up was a pig shifting, the 10WT made a huge difference and hasnt changed performance in the summer either.

make sense?

 

[Tinstar]

I'm just north of you and it's hot here also.
I Run this in mine.
Works like a dream.
They also make it in 30wt and 50wt.

I would not run dex fluid unless you need to rebuild trans soon.
Military uses 15w-40 because of logistics. Not the best for long life.

 

[LanceRobson]

As Tinstar noted some of the military fluid choices are driven more by the strong desire to reduce the number of fluids a unit has to drag around the field with them than what the manufacturer specs. A case in point is the Chevy CUCVs in which the US military specs 15-40 engine oil but the sticker from the factory that's on the back of your sun visor specs 30 WT above 40 degrees and 5-30 WT below 40 degrees. 5-30 was used until all the bigger engines went to 15-40 and so the CUCVs followed suit. Uncle Sam also changes most fluids more frequently than commercial users do. So, I have always eyed military Lubrication Orders with a bit of skepticism.

Allison approves specific engine oils and transmission fluids for off road use and transmission fluid for on road use and I'm pretty sure they are all synthetic. You might want to look at this....

http://www.allisontransmission.com/parts-service/approved-fluids

When I used the calculator based on our usage on and off the farm it came back with a 100,000 mile fluid change interval with the internal filter changed only at overhaul and the aux filter changed at 50,000 miles.

When using the calculator Allison defines "severe duty" as stopping more than once per mile and not by road speed or hours. When I input "severe duty" out of curiosity the fluid change interval dropped to 15,600 miles with an aux filter change at 7,800 miles. That's food for thought for those who do a lot of low speed or stop and go operation.

Each of us ought to make our own decisions based on how we use our trucks and Allison gives a good tool to do that. A synthetic transmission fluid change isn't cheap but it sure beats the heck out of a transmission overhaul.

For those who prefer to use printed data here's a link to Allison fluid and filter change interval charts in PDF format (note that it's 28 pages):

https://www.google.com/url?sa=t&rct...bjcEwHnbw&sig2=fDr8mIM8A2p5lyHkPKsQRg&cad=rja

I hope some of this rambling helps....


Lance

 

[Buffalobwana]

Thanks WYomer and Lance. Lots of good info there. I'll keep 15-40 in it for the summer. If I change it I'll look at a synthetic or I'll look at the Allison site. Thanks for the link.

You are right. A synthetic change is pricey, but Allison transmission change is more pricey. If all you do is take it to get ice cream and drive in the 4th of July parade, I suspect you could get away with almost any approved fluid. If you work it, it's worth the money to take care of your machine.

 

[Tinstar]

Thanks WYomer and Lance. Lots of good info there. I'll keep 15-40 in it for the summer. If I change it I'll look at a synthetic or I'll look at the Allison site. Thanks for the link.

You are right. A synthetic change is pricey, but Allison transmission change is more pricey. If all you do is take it to get ice cream and drive in the 4th of July parade, I suspect you could get away with almost any approved fluid. If you work it, it's worth the money to take care of your machine.

If it's hardly driven then it's even more important for the correct fluid.
Wrong fliud won't handle the moisture and prevent corrosion when sitting for weeks on end.
Plenty of threads on here about that and the 10w vs dex or whatever.

The Mobil oil I mentioned meets/exceeds all of Allison specs.
Going strictly the Allision branded fluid isn't required since at least this one is as good or better than factory and its Allision approved.
All the Allision Military transmissions leave the factory with 10w oil.
The military is the one who swaps the fluid at first service.
They have almost an unlimited supply of parts. So trashing a tranny isn't a huge deal money wise to the unit.

I personally would swap.
That heavier oil is hard on it.
The transynd is worse. Several threads on guys that swapped and weeks later were replacing or rebuilding the trans.
Big $$$!!

It was born with 10wt.
It will live the longest on that.

 

[Floridianson]

You used 15/40 should have just gone with a 10 weight. What was in there could have been lighter than what you put in. I do not mind the hard shifts. I believe you can stick with MO just drop it down in weight. I believe when loaded/overload you want fast and strong up and down shifts. Since most of use do not go there then a MO is it lowest form that you can find will be fine with Allison specs. Also the proper change out to ATF works with fingers crossed that it does not clean the Trans. too well and something goes wrong.

 

[WYomer]

If it's hardly driven then it's even more important for the correct fluid.
Wrong fliud won't handle the moisture and prevent corrosion when sitting for weeks on end.
Plenty of threads on here about that and the 10w vs dex or whatever.

The Mobil oil I mentioned meets/exceeds all of Allison specs.
Going strictly the Allision branded fluid isn't required since at least this one is as good or better than factory and its Allision approved.
All the Allision Military transmissions leave the factory with 10w oil.
The military is the one who swaps the fluid at first service.
They have almost an unlimited supply of parts. So trashing a tranny isn't a huge deal money wise to the unit.

I personally would swap.
That heavier oil is hard on it.
The transynd is worse. Several threads on guys that swapped and weeks later were replacing or rebuilding the trans.
Big $$$!!

It was born with 10wt.
It will live the longest on that.

Curious I spent lots of times on the fluid threads and the main thing I saw was 15-40 has its lovers and haters and Alison says get it out. But the guys that swapped to 10WT are neutral and the Transync guys are doing really well...its the Dextron guys that have had the most rebuilds. Is that not what you saw?

Im running Transync and loving it FYI at 7000ft above sea level tempature range is -40 to 100F operating temps.

 

[Tinstar]

Was referring only to what I read on SS and other forums.

If it's working for you then great!

I personally wouldn't do transynd in these big trucks.
I only run it in my Allison 1000 series that's in my GMC 2500HD.

In my big stuff...10wt.

To each his own.

 

[Buffalobwana]

Curious I spent lots of times on the fluid threads and the main thing I saw was 15-40 has its lovers and haters and Alison says get it out. But the guys that swapped to 10WT are neutral and the Transync guys are doing really well...its the Dextron guys that have had the most rebuilds. Is that not what you saw?

Im running Transync and loving it FYI at 7000ft above sea level tempature range is -40 to 100F operating temps.

Id hate to start a "what's the best fluid" war, or a "Ford vs Chevy" war of transmission fluids, but, now I'm curious. We have claims that switching to Dexron and/or switching to Transyn will destroy your transmission, cause loose stool, hair loss and pryopism among other ailments.

I did a search but didn't see trashed trannys from one fluid or another? Anyone have examples or proof that ones tranny got wrecked by Dexron or Transynd?

Maybe I'll just go back to 10 wt.

 

[98G]

My understanding is a change from one fluid to another is a bigger detriment than choice of fluids.

I see a correlation with Trans fluid changes and failures.

I leave mine alone unless it looks like there's a problem.

 

[Buffalobwana]

I have no experience other than this change to 15-40. It now shifts like butter, runs cool, even over the passes of 10k feet but drives like I am pulling dead weight when I am starting up from 0 to when the turbo kicks in. Now that I'm home and switching between the other two trucks, it's obvious. Something is definitely different. (All three are identical M923A2's)

I guess there is the chance that the guys I paid to do the fluid hit something on the motor? Made an "accidental adjustment" with a slipped wrench? Or should I just go back to 10wt (which was probably what was in it to start with). Since I don't know the original fluid. It was gold, so probably motor oil.

The change in performance was noticeable to me when I pulled out of the drive after the change. Now with the other two trucks to compare it to, I know I'm not imagining it.

 

[Suprman]

There is a trans fluid pressure adjustment. Basically makes shifts harder or softer. It's on the throttle assembly it's like a kick down cable on a Chevy. Bringing the cable in closer will increase fluid pressure.

 

[Buffalobwana]

There is a trans fluid pressure adjustment. Basically makes shifts harder or softer. It's on the throttle assembly it's like a kick down cable on a Chevy. Bringing the cable in closer will increase fluid pressure.

Would it also effect the power output at the start? Shifts were definitely noticeably smoother.

 

[Suprman]

Thinner fluid may need a slight up adjustment to match the shifts with thicker fluid. With more pressure it feels like it holds the gear slightly longer then shifts hard to the next gear. Not sure if it's actually quicker but it does give that feel. generally you want more pressure for really heavy hauling.