Trans service and trans temp expectations/max safe.

[Zach6.7CTD]

Hey guys. Bought my truck in jan with 120k on the clock. Decided to get the trans serviced before I take it out of state pulling a trailer next weekend. Trans fluid didn't look or smell bad however I've heard horror stories of people using non mopar filters in the trans and having the screw on filter come off and ultimately destroy the trans. Anyway. Had trans serviced and had my mopar trailer brake module activated.

When I checked fluid "cold" idling in N sat morning with trans temp fluctuating between 91 and 93°F the fluid on the dipstick showed just on the low side of half way between cold and hot. Is this considered over full and should I be concerned? Truck seems to run and drive just as good as before if not a bit better.

Also. I'll be pulling a 7x14 twin axle em loses cargo trailer next weekend with. Load weight of 4k to 6k lbs. What should I expect for a normal range of trans temps. Also what is considered the maximum safe temp for both long and short duration pulling. Last thing I want to do is shorten the life if this thing!

Thanks guys.

 

[transe]

You may be slightly overfilled. For the 68RFE transmission, the dipstick markings should have the COLD zone at 7-14 mm from the tip of the stick, and the HOT zone at 46-54 mm. So halfway between the COLD and HOT zones would be 30 mm from tip of stick. At 93°F your fluid level should be 17-25 mm from tip of stick (so nominal level is 21 mm).

So 25 mm at 93°F would be OK. Sounds like yours may be around 28 mm (judging from your description). Not an emergency by any means. I would double-check it again when warmed up and see what it reads. It can be very difficult to get an accurate level reading (and achieve a correct fluid level) after a fluid change, since residual fluid on the inside of the filler tube can smear on the stick and give you a false "high" reading.

Attached is a fluid level chart for 68RFE that gives min, nominal, and max level (in mm from tip of stick) for each temperature. This should be more helpful than the simple COLD and HOT zones when setting your fluid level.

View attachment 68RFE Oil Level Chart2.pdf

 

[crispyboy]

Great information in this post.

Question from a novice:
Why does the level of transmission fluid change so much as the temperature goes up? Why does power steering fluid do the same?

 

[transe]

Question from a novice:
Why does the level of transmission fluid change so much as the temperature goes up? Why does power steering fluid do the same?

Because the fluid density changes with temperature. As the fluid heats up, it expands, which raises the level.

This is why it can be a challenge to design the proper oil level for a transmission. The trans must operate from very cold temperatures (-40°F) to very hot temperatures (275°F+) without fluid being so low that the filter sucks air, and without being so high that the fluid gets into the geartrain (which churns it up and foams the fluid). But the level changes dramatically as the temperature changes. Not only that, but the trans also has to endure angle changes (going up or down steep grades, or going sideways along a slope), plus the G forces that come from acceleration, panic braking, and extreme cornering. So designing the transmission oil pan and fluid level is not a simple task!

 

[crispyboy]

Thanks for taking time and explaining the fluid dynamics.

 

[AH64ID]

Zach, you should fill out your signature so everyone can see the specifics on your truck.

 

[Zach6.7CTD]

10-4. New here and haven't had a chance to yet.

 

[BaldwinScott]

Is there a chart for the Aisin Trans levels?

 

[HorseMan-AR]

As always, thanks to Transengineer for the detailed reporting. Smart guy!

Curious, Transengineer, can you provide the same document/link for the Aisin transmission?

 

[Zach6.7CTD]

Transengineer I'll try and get a picture of where my level is on dipstick compared to temp reading in my evic.

 

[transe]

Curious, Transengineer, can you provide the same document/link for the Aisin transmission?

Sorry, I don't have a similar table for the Aisin at the moment. I will see if I can dig something up...

 

[gsbrockman]

Doesn't the 68RFE dipstick specify checking the fluid in Park??? Going off memory here, as I sold my 2007.5 in 2013.

 

[Mingoglia]

All this talk has now made me nervous to one day change the fluid in my '15...and even MORE nervous to have the dealer do it as I always have to wonder if they have the same attention to detail as I...

 

[gsbrockman]

All this talk has now made me nervous to one day change the fluid in my '15...and even MORE nervous to have the dealer do it as I always have to wonder if they have the same attention to detail as I...

A little time consuming for the sump filter replacement at 60k miles, but the first 30k service is strictly a drain & fill of the fluid only.
https://www.turbodieselregister.com...r-in-an-Aisin-AS69RC-equipped-RAM-3500-pickup

 

[transe]

Doesn't the 68RFE dipstick specify checking the fluid in Park??? Going off memory here, as I sold my 2007.5 in 2013.

Yes. You can actually check the fluid in Park or Neutral (they are identical from a hydraulic standpoint), but we recommend Park from a safety standpoint.

 

[Zach6.7CTD]

My dipstick days to idle in neutral. Says nothing about park. Anyway. Just to clarify. What temp range is considered "safe" "caution" and "DANGER"

 

[transe]

My dipstick says to idle in neutral. Says nothing about park. Anyway. Just to clarify. What temp range is considered "safe" "caution" and "DANGER"

We consider 180°F as "normal operating sump temperature." Personally, I would not be concerned (when towing, in stop and go traffic, etc.) if the sump temp reached 200-210°F. Once it started going above 210°F, I would keep an eye on it and see if I could cool things down. I would try to avoid anything above 230°F.

Now, having said that, realize that temps above this will not instantly kill your trans. But life decreases as temp increases. So you will be wearing out your trans faster as the temp rises. For example, trans life at 230°F sump temp may be only 10% of what it would be at 180°F. That sounds really bad, but consider: If your temp spikes up to 230°F for a couple miles during a grade climb, then that 2 miles (at 230°) did the same damage to your trans as driving 20 miles (at 180°). So not as big a deal as you might think. SHORT excursions to high temps are not necessarily horrible. But you wouldn't want to drive all day at 230°F!

A couple tips to help keep it cool:
• When towing up a steep grade at low speeds, manually downshift the trans to the lowest possible gear (1st if possible), or use 4 LOW range.
• When stopped at a light, shifting the trans to Neutral will reduce the amount of heat being generated.

 

[Bug Out]

TransEngineer, Does the transmission TC lock in first? I thought making the TC lock cools things down.

 

[transe]

TransEngineer, Does the transmission TC lock in first? I thought making the TC lock cools things down.

No, the TCC does not lock in 1st gear. But what happens in many cases (when towing heavy at slow speeds up a steep grade) is the trans will shift to 2nd, and either run unlocked in 2nd gear, or it will lock the TCC in 2nd, but then the torque drops off (due to TCC engagement) so truck slows down, whereupon TCC unlocks again.

If the TCC will lock (and STAY locked) in 2nd, then you can pull in 2nd gear. But if the TCC is unlocked in 2nd gear, then downshifting to 1st will greatly reduce the amount of slip in the converter (and thus, the amount of heat generated).

 

[Newsa]

A couple tips to help keep it cool:
• When towing up a steep grade at low speeds, manually downshift the trans to the lowest possible gear (1st if possible), or use 4 LOW range.
• When stopped at a light, shifting the trans to Neutral will reduce the amount of heat being generated.

1) I always thought it was hard on the drivetrain to run 4 low on dry pavement. But there was a guy with a 35 ft 5 er at Roan Mtn State Park (2012 CTD 2500)who said to get up the paved 12-15% grade, he puts it in 4 low and lets it idle up the hill.
He has the 68rfe. So, I guess I've been a bit too worried about short stints of 4x4 on dry pavement.
I did end up using 4x4 to back the travel trailer into tight spots up a steep uncline after first letting my clutch slip a bit too much. So steep, I was spinning rear wheels on dry pavement with limited slip differential.

2) When driving my dad's RV, I often shifted to neutral at stop lights. But the jolt is big on a 4.28 rear end when shifting back into gear. I guess the drivevtrain is made to withstand jolts. But was concerned about the increased number of jolts you get when shifting at stop lights. Seems like the increased number of jolts might put undue stress on u joints?