My trans oil swap to ATF

[Wingnut13]

Hey all,

This seems to be a topic that I see lots of questions about but not many answers. So for the benefit of others thinking about doing the swap I'll throw my trans oil change experience knowledge up here...... should be a short write up.

My truck is a 2003 3126 Cat equipped unit with the Allison 3000 series as per standard. With 13,500 miles on the truck as I received it the transmission would shift HARD when the temp was low, a bit better when it was warmed up. I live in NH where a good bit of the time it's cold here. I noticed as the fall weather made the red line on the thermometer shorter by the day the shifting got a bit more abrupt without a good warm up. I had been considering the change to ATF but the cost had me waiting. I had a set of filters on standby ($35 from the usual suspects). A visit to the local discount importer changed my mind. They had a few cases of an Allison rated fluid (Sunoco ATF) at a good price. I talked with the owner, hey, if I buy you out of the oil will you give me a break on the price? Sure... how about $3.25 a quart? done. Four cases plus four more loose quarts and I was out of there for under $170. Total oil change filters and fluid $205.00

I wasn't excited about the oil being in quarts, turns out it wasn't a bad thing. So on a Sunday afternoon the temp warmed up to 38 and I took the truck for a ride to get the fluid warmed up. I got the engine up to 165 degrees, about as good as it will get I figured I headed home. First the transfer case was drained, then the transmission itself. I used a 1 gallon Rotella oil container with one side cut out to catch the fluid from hitting the exhaust and deflect it directly into the five gallon bucket. Total drained was five gallons. This is when I realized the warm engine oil was the same viscosity as the cold ATF, interesting. I disconnected the return line hose and directed it into the bucket, added three gallons of ATF. Started the truck and pumped out about two gallons of brown fluid, added another two gallons of ATF. Started the truck and pumped out another two gallons of brown, then mixed fluid. Added more ATF, started the truck, then clear ATF was now coming out of the return line.

Next I swapped the filters, didn't drop the driveshaft. To get around the driveshaft issue I separated the filter and cap once pulled out of its hole. This gave the clearance to pull them out without moving the driveshaft. Then I topped off the trans with ATF, hooked up the cooler return line and all was good. In all 10 gallons of fluid was used. I would like to go to the new spec'd fluid, but don't have the cash for that now. I think the ATF is a good in between.

How does it drive? Well, shifts are now smooth like a bus. Obviously you still have some pretty big gearing jumps between ratios, but the handoff is much better. I have not been able to find out how to get the trans to "learn mode" yet. I've had one issue, I have had a bit of "flare" on shifts when the trans is warmed up. I'd think it would be fixed with a re-learn. I have only put 70 miles on since the change. My take on engine oil in the trans..... Probably best for where it's hot, otherwise its hard on components. I don't have a trans oil heater, and have no time to put a salamander heater on the trans before I go drive. If I lived in the South, I'd probably just stay with the engine oil.

~Wingnut13

 

[Reworked LMTV]

Hey all,

This seems to be a topic that I see lots of questions about but not many answers. So for the benefit of others thinking about doing the swap I'll throw my trans oil change experience knowledge up here...... should be a short write up.

My truck is a 2003 3126 Cat equipped unit with the Allison 3000 series as per standard. With 13,500 miles on the truck as I received it the transmission would shift HARD when the temp was low, a bit better when it was warmed up. I live in NH where a good bit of the time it's cold here. I noticed as the fall weather made the red line on the thermometer shorter by the day the shifting got a bit more abrupt without a good warm up. I had been considering the change to ATF but the cost had me waiting. I had a set of filters on standby ($35 from the usual suspects). A visit to the local discount importer changed my mind. They had a few cases of an Allison rated fluid (Sunoco ATF) at a good price. I talked with the owner, hey, if I buy you out of the oil will you give me a break on the price? Sure... how about $3.25 a quart? done. Four cases plus four more loose quarts and I was out of there for under $170. Total oil change filters and fluid $205.00

I wasn't excited about the oil being in quarts, turns out it wasn't a bad thing. So on a Sunday afternoon the temp warmed up to 38 and I took the truck for a ride to get the fluid warmed up. I got the engine up to 165 degrees, about as good as it will get I figured I headed home. First the transfer case was drained, then the transmission itself. I used a 1 gallon Rotella oil container with one side cut out to catch the fluid from hitting the exhaust and deflect it directly into the five gallon bucket. Total drained was five gallons. This is when I realized the warm engine oil was the same viscosity as the cold ATF, interesting. I disconnected the return line hose and directed it into the bucket, added three gallons of ATF. Started the truck and pumped out about two gallons of brown fluid, added another two gallons of ATF. Started the truck and pumped out another two gallons of brown, then mixed fluid. Added more ATF, started the truck, then clear ATF was now coming out of the return line.

Next I swapped the filters, didn't drop the driveshaft. To get around the driveshaft issue I separated the filter and cap once pulled out of its hole. This gave the clearance to pull them out without moving the driveshaft. Then I topped off the trans with ATF, hooked up the cooler return line and all was good. In all 10 gallons of fluid was used. I would like to go to the new spec'd fluid, but don't have the cash for that now. I think the ATF is a good in between.

How does it drive? Well, shifts are now smooth like a bus. Obviously you still have some pretty big gearing jumps between ratios, but the handoff is much better. I have not been able to find out how to get the trans to "learn mode" yet. I've had one issue, I have had a bit of "flare" on shifts when the trans is warmed up. I'd think it would be fixed with a re-learn. I have only put 70 miles on since the change. My take on engine oil in the trans..... Probably best for where it's hot, otherwise its hard on components. I don't have a trans oil heater, and have no time to put a salamander heater on the trans before I go drive. If I lived in the South, I'd probably just stay with the engine oil.

~Wingnut13

Transmission fluid get heated by the engine. Plain oil was used due to availability. I assume that your Sunoco was synthetic? Heat is what destroys transmissions typically. In the South, Transyn Allison or equivalent is best.

 

[Wingnut13]

If I had to guess I’d put money (environment dependent) that the trans HEATS the engine coolant almost as much as the engine. Not something I’m passionate about…. Just sayin’

No, I did not use synthetic. Just thelisted TES 389 spec’d fluid. This is an interim step on the way to synthetic.

I understand engine oil is easy sub. We’ve spent the last 20+ years in hot environments with these trucks. New Hampshirite is not that. Though I’m sure the trucks at work still have engine oil and certainly do not follow the recommended preheat in cold wx.

If I get a chance this week I’ll pull a dipstick on one of the new trucks and see what they are running.

 

[Wingnut13]

And yeah after years of wheeling in New Mexico I’ve learned heat kills transmissions faster than anything!

 

[glcaines]

When I changed the motor oil to Dexron 3 in my M35A3, I drove the truck for several miles between flushes, making the transmission shift up and down repeatedly, to make sure I got all of the motor oil out. Allison Technical Support recommended that I do the driving when switching fluids.

 

[Wingnut13]

, Seems I may have skipped a step….huh

 

[Reworked LMTV]

, Seems I may have skipped a step….huh

Don't think it is absolutely crucial, since you end up with a synthetic blend. Better than plain oil.

 

[Wingnut13]

FYI I did check our trucks at work. They have been updated with Allison Transynd fluid. Motorpool has a 55gal drum of it hiding in the corner of the shop. They wouldn't leave me alone with it.........

 

[glcaines]

Don't think it is absolutely crucial, since you end up with a synthetic blend. Better than plain oil.

I talked directly with an Allison engineer at the factory about my 1545 transmission when I changed to Dexron 3. The guy was adamant about driving the truck and having multiple gear shifts up and down between drains and refills with Dexron 3 and to go through several drain and refill cycles as well as replacing the filter afterwards. He said that the motor oil and Dexron 3 were not compatible and that gum would form in the transmission if only a little motor oil remained. In the 1545 transmission you can't use any Dexron fluid higher in number than Dexron 3 because the seals are only compatible with Dexron 3. After switching to Dexron 3, my 1545 transmission shifted up and down much smoother, a significant improvement.

 

[Reworked LMTV]

I talked directly with an Allison engineer at the factory about my 1545 transmission when I changed to Dexron 3. The guy was adamant about driving the truck and having multiple gear shifts up and down between drains and refills with Dexron 3 and to go through several drain and refill cycles as well as replacing the filter afterwards. He said that the motor oil and Dexron 3 were not compatible and that gum would form in the transmission if only a little motor oil remained. In the 1545 transmission you can't use any Dexron fluid higher in number than Dexron 3 because the seals are only compatible with Dexron 3. After switching to Dexron 3, my 1545 transmission shifted up and down much smoother, a significant improvement.

Can't claim expertise on trans fluids, but my motor oil to Transyn in an M3070 seems to be gum free and smooth.

 

[glcaines]

I have no idea about the compatibility of Transynd and motor oil. Transynd is way too expensive for my budget.

 

[BKubu]

My first move when I used to get a truck with an Allison transmission was to take it to Allison for servicing. They would do a fluid swap and check everything out. When I got there, they always asked me if I wanted 15W40 back in. I asked them what they'd recommend and they told me Transynd (preferably), or Dexron, and recommended multiple changes as GLCAINES has stated. I always went with Dexron since I don't drive my trucks for thousands of miles each year (and cost).

 

[Reworked LMTV]

My first move when I used to get a truck with an Allison transmission was to take it to Allison for servicing. They would do a fluid swap and check everything out. When I got there, they always asked me if I wanted 15W40 back in. I asked them what they'd recommend and they told me Transynd (preferably), or Dexron, and recommended multiple changes as GLCAINES has stated. I always went with Dexron since I don't drive my trucks for thousands of miles each year (and cost).

I have no idea about the compatibility of Transynd and motor oil. Transynd is way too expensive for my budget.

Talk to this guy, he's an expert:

"hzjcm8" from Duramax Forum.

"Former Transmission Fluids Engineer, GM Powertrain and Allison Transmission, Inc. (1983-2009)"