NAG1 Transmission Fluid Change


UK 2004 T1N 313CDi
But also the cooler in the radiator has the ability to warm the transmission fluid!

With it removed you seriously run the risk of your transmission never reaching operating temperature and suffering potential damage.

If you must persist with your after market remote cooler you will have to add a thermostat to allow the transmission to reach full operating temperature. And remember that you cannot simply block the flow until temperature is reached, you will have to allow the flow to bypass your new cooler.

In short MB engineered a VERY robust system and you will be hard pushed to improve on it.

My view, revert to standard as soon as possible.

Keith. (20+ years experience working in cooling system development for a major UK manufacturer of 4x4's and performance sport cars).


Well-known member
One wonders WHAT you hope to gain by adding the aftermarket/auxiliary transmission fluid cooler?
I see that you are from Vermont.....does it not get rather cold in the winter months in Vermont?
How will your transmission fluid be warmed up in the winter months?
Transmission fluid that never gets up to the engineered best operating temperature (+- 20 deg. F from the
engine coolant temperature) may be worse for your transmission than occasionally running a few degrees warmer
than the engine coolant temperature in the summer months.
What is it that you are hauling/towing that leads you to believe that Mercedes Benz engineers missed something
about the transmission fluid heating and cooling characteristics of your T1N Sprinter.
Do you tow a trailer that weighs > 5,000 lbs.?
Is your normal Sprinter weight heavier than 7,000 lbs.?
I used to run my 2006 T1N Sprinter all over the eastern half of the USA, towing a ~5,000 lb. cargo trailer, in the
hottest months of the summer, and the transmission fluid temperature was the least of my worries.
I often had to manually downshift out of OVERDRIVE 5th gear down to 4th gear (1:1) to keep the engine coolant temp a bit lower, keep the RPMs up
in the most efficient/best fuel mileage/best performance range (2600-3100 RPM), when climbing grades or heading into strong headwinds.
I manually downshifted for heavy traffic situations (try Chicago during the afternoon/evening rush hours) to maintain higher RPM to get better
cooling and reduce the % engine LOAD.
So, what is your rationale for adding an additional trans fluid cooler that will compromise the well engineered transmission HEATING and COOLING
system that was designed into your Sprinter by MB engineering?


New member
Thanks for the input. My 3500 weighs in at 9,500# on a daily basis. I occasionally pull trailers, one
is a 5,000 dump trailer and the other is a 12' V-nose enclosed job site trailer.
My rational is, that any other vehicle I've purchased and ordered with "towing package" came with
an auxiliary tranny cooler. This one the dealer added the hitch only. Also I read that most tranny
failures are due to overheating.
I haven't read anything yet about too cool of fluid caused transmission problems, only too hot.
I do plan to turn the vehicle into a RV in a couple of years and travel pulling a trailer. I was just
trying to prepare it for that. :thinking:


VW has a nice thermostat (opens at 75*C) on the Touareg V10 transmission. And newer Benzes have a similar one that opens higher IIRC. The only caveat is that you need their fittings, you can't easily DIY around them.
It bypasses the cooler when it's closed.

Behr TO 9 75 is the code for the VW part.

I pieced up a complete setup (cooler, Touareg lines, new thermostat) just because I fear a cracked transmission cooler and I wouldn't want to see my freshly rebuilt transmission contaminated with anti-freeze.

Aqua Puttana

Poly - Thread Finder
I have been reading this thread and there seems to be a lot opinions on fluid for the T1N trans. Do I need to use MB fluid on a sprinter with 230000 miles on it? or can I just use any MB Spec 236.14 trans fluid?
If you believe the science of MB BeVo as to meeting the specs you can use any of the MB236.12, MB236.14, (possibly even MB236.10 for T1N) fluid regardless of brand label.

From the information that I've seen the MB236.14 fluid was actually created for transmissions other than the NAG1, but it may be the easiest to obtain.

I use Shell ATF 134 purchased in case lots from an industrial lubricant supply house MB236.14 spec.



BeVo 231.0 said:
3.) Automatic transmission fluids (ATF), sheet 236.1/.2/.3/.6/.7/.8/.9/.10/.11/.12/.13/.14/15/.16/.17/.20/.21/.25/.26/.41/.81/.91

ATF are comparatively low-viscosity gear oils which, due to their universal use potential as a gear oil or a hydraulic fluid, can cover a wide spectrum of applications. The ATFs in the individual sheets differ essentially due to their inherent friction coefficients in tribological contact. This property makes these oils ideally suited for use as functional liquids for automatic transmissions, the shifting comfort of which is heavily influenced by the behavior of the friction value of the ATF, among other things. Therefore, to achieve optimum performance of the vehicles, only the ATF quality (sheet no.) assigned to the major assembly is to be used. The individual ATF qualities will be described in greater detail below.
<selected snips>

Automatic transmission fluids (ATF), sheet 236.10, for MB automatic transmissions with and without controlled torque converter lockup clutch (GKÜB) in passenger cars. These ATF are installed ex works as lifetime oil in all MB automatic transmissions 722.6 with controlled torque converter lockup clutch. In the event of repair work, only the ATF quality shown in sheet 236.10 can be used for refilling in this new generation of automatic transmissions.

Automatic transmission fluids (ATF), sheet 236.12, for 7-speed automatic transmissions are also downwards-compatible for all 5-speed automatic transmissions.

Automatic transmission fluids (ATF), sheet 236.14, for 5-speed automatic transmission 722.6, 7-speed automatic transmission 722.9 in combination with engine 629 irrespective of the production period and the installed oil pan, 7-speed automatic transmission 722.9 up to transmission sequence number 2834526 except vehicles with engine 629, 7-speed automatic transmission hybrid 724.2.
(Interesting to note that there are references to specific 7 speed transmissions. In my mind that hints as to why the MB236.14 spec was created.)

See also:

The easy answer is to use MB236.14
Last edited:

Aqua Puttana

Poly - Thread Finder

Aqua Puttana

Poly - Thread Finder
Yeaht that is for the Shell stuff, is that as good as the stuff I got?

If you believe the science of MB BeVo as to meeting the specs you can use any of the MB236.12, MB236.14, (possibly even MB236.10 for T1N) fluid regardless of brand label.

I use Shell ATF 134 purchased in case lots from an industrial lubricant supply house MB236.14 spec.

Using my 50 - 60,000 tranny fluid OCI I don't bother with a new filter every time anymore. TC and pan drain, good to go. I know that a filter change every other OCI is ok and conservative. Coming up I'm leaving the 2004 filter as is for the 2nd no filter fluid cycle. I'm not worried at all.

My 2004 - 2006 transmission filter was sized for the "change once and never again" program. (What were they thinking?) It must have been a bit over-sized with that program in mind. Back when I did drop the pan my donut magnet showed less and less accumulation with each subsequent change. My other brand vehicles had 100,000 mile tranny OCI.

Great advice. :thumbup:

Talkinghorse43 provided a filter media picture in the quoted thread above. (Click the blue arrow icon.)
Last edited:


New member

I'm in Europe and the service manual mentioned early on in this thread is either not available or not find-able. Could someone possibly give me the title/publisher of the service manual that would include working around the auto transmission please?


Well-known member
Don't wait until your tranny connector looks like this. About 10K miles ago it was barely weeping. Now, it's leaking bad. Time for some TLC.

The dreaded wicking along the control lines is happening. Here's the transverse section where it crosses behind the spring, bound for the electrical connections area under the driver's seat. You can clearly see how the tranny fluid has crept along the line. Note that the fluid isn't being blown back here, his section is forward of the transmission connector.



Well-known member
Dr A sold me a new connector when I visited him in PA. He said that they commonly developed leaks and that I should carry a spare. That was nearly ten years ago when Frito had less than 15k miles. I still have the part, and I'll have the boys at Lone Star Motors in Calgary install it when they do my tranny service next week. Hopefully the new connector end will stop the leak.

I don't know what to do about the wiring loom. I'll point it out to the tech and see if they think any further action is required.


New member
I like to add a couple of comments about removing transmission pan and drain plug. I have 2008 Sprinter 2500 cargo 144 wb GAS engine 3.5 , i know I'm the minority , but may help those with gas engines / I could not drop transmission pan - not enough clearance , the cross member bar towards front of pan was blocking me from removing pan. i remove transmission mount bolts near where trans connects to drive shaft. Then I remove the two motor mount bolts toward front of motor. I jack the front of motor @ 3 inches and using bullet jacks placed block on top off jack to hold it up. I bought 2 extra long bolts for transmission mount and thread it in a few turns , then place a small 2x4 under 2 bolt and lifted it up a few inches also. This gave me enough to remove pan. To remove transmission drain plug that was on there so tight it actually broke the Allen wrench off inside drain plug ,I was using a cheater bar on Allen wrench, I had soaked it with liquid wrench before and let it sit for more than 6 hrs before attempting to remove drain plug. So after small piece of Allen wrench broke off , I was lucky it came out by tapping a couple of times with hammer. Then I used a Allen wrench with my air gun and drain plug came off easy , i was glad that drain plug was not strip with all the trouble I had trying to remove with Allen wrench. I did remove plug before removing bolts. I was actually changing the solenoid pack, it went into limp mode.I used the Valvoline brand transmission fluid , was not sure that this was going to be a good fix, didn't want to use the expensive MB fluid until I was for sure this was a good fix . did purchase a scan tool to clear codes. I have not replace fluid yet with MB brand , it's been a about a month or so @ 6-8 k mile with Valvoline brand , shifts good and smooth , feels normal.I will be replacing fluid very soon with MB brand . I did use torque wrench from harbor freight to torque all bolts for solenoid pack and transmission bolts, it's pretty acurate . Hope this helps someone !

Aqua Puttana

Poly - Thread Finder
I like to add a couple of comments about removing transmission pan and drain plug. I have 2008 Sprinter 2500 cargo 144 wb GAS engine 3.5 , i know I'm the minority , but may help those with gas engines / I could not drop transmission pan - not enough clearance ,
Your clearance problems are an NCV3 body style issue, not a T1N issue. This is the T1N section.

Thanks for the general input.

:cheers: vic


New member
Silver Star Transmissions sells a kit including fluid, filter, gasket, and pilot bushing (wire feed through) for $98.00. Don't know about shipping. I live nearby and pick it up.

Top Bottom