Transmission noise/vibration cured with DARF

TODAY I had my '02 NAG1 Auto transmission serviced with Dr. A's DARF cure, and can't believe I'm driving the same van. NO Noise, no vibrations throughout the van at certain RPMs, with no changes to the driveline/shaft bearing support, no change in oil levels, just DARF's precision hole drilled with easy but exact instructions. That Rumple Strip noise and shudder is gone and hopefully soon forgotten. Thanks Andy, the SPRINTER FIXER UPPER.
Buy a DARF KIT today from Dr. A.

Which drill bit did you use? The .05 or the .04?

Thanks, Drew

Drew.eight said:

Which drill bit did you use? The .05 or the .04?

Thanks, Drew

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I did .05.


I just drove 1000 miles, and really did not notice a fuel economy drop

#5 drillbit used

NelsonSprinter said:

#5 drillbit used

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So nobody makes a big mistake, I don't believe it was a number 5 drill bit. A typo maybe?

#5 drill bit = 0.2055" or 5.220 mm

If my memory is correct, I used a #56 drill bit for my early DARF Doktor A test trial.

#56 drill bit = 0.0465" or 1.181 mm

#5 is WAY bigger. It's unlikely anyone would be confused if they chucked up the #5 drill bit and lined it up, but you never know....

vic

He sends a 55 and a 56. I just didn't want to let the cat out of the bag..... I guess you still need to buy the kit to find out where to drill... Just wondering what most people are using before I do mine. The paperwork says the smaller one is for maximum fuel economy. Does anyone know what the mpg difference is between the 55 and 56??

Thanks,
Drew

still patiently waiting for my D.A.D

Drew.eight said:

He sends a 55 and a 56. I just didn't want to let the cat out of the bag..... I guess you still need to buy the kit to find out where to drill... Just wondering what most people are using before I do mine. The paperwork says the smaller one is for maximum fuel economy. Does anyone know what the mpg difference is between the 55 and 56??

Thanks,
Drew

still patiently waiting for my D.A.D

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Sorry.

I did the larger, the .056, and did not notice any real difference in mileage on my 1100 mile journey recently.

I'd guess minimally. I ended up using the larger bit - really didn't want to do it twice if I still had RSN if I started with the small bit. I haven't noticed a drop in MPG's - maybe 1 or 2 at the most. But it's also hot and running both AC's really cuts the mileage. I'll know better when it cools off.
Shifting is incredibly smooth now.
Bruce

Oops. I thought the basic procedure had been outlined already.

So I didn't consider it a secret.

The DARF kit from the good Doktor A is worth his price to make certain you have everything you need to do it correctly. Even if you are not plagued by RSN, my transmission just seems so much smoother after the modification that it's worth doing the mod for that alone. I haven't noticed a mpg decrease, but I'm not a calculate mpg with every tank type person either.

vic

Pardon the from a non-owner and newby on the forum... but...

When I was surfing around the forum and saw "RSN" I thought to myself "Rumble strip noise? Naw... has to be a coincidence." But it wasn't. When I read the posts from Doktor A talking about the torque converter bypass clutch, I was floored.

You see, I had hands-on experience with another vehicle a number of years ago with the very same problem, and had a several-month-long dialog with the manufacturer's engineer assigned to the issue while we mutually diagnosed it. In that case, it was discovered that bypass clutch slippage was prematurely aging the transmission fluid, causing the fluid's friction constants to fall out of the engineered range. They kept messing with the shift control computer to change the hysteresis points (upshift/downshift spread) by delaying lock/unlock action to keep slippage under control. But it turns out that the real solution was to change the fluid 4X more frequently than the originally recommended 60K miles. Also, we learned to absolutely avoid aftermarket fluids with synthetic oil components, which exaggerated the slippage.

Also, that transmission was only concerned with 100% lockup in the tallest two gears, not all gears, nor a variable bypass. So Andy's fluid relief orifice trick is clearly genius. Heck, beyond genius. But hopefully without getting into probably painful, old discussions, I still have to ask - has anybody attacked this bug by changing the fluid?

Mr. Pixel said:

But hopefully without getting into probably painful, old discussions, I still have to ask - has anybody attacked this bug by changing the fluid?

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Yes, but as you discovered in your experience, it eventually returns. Most, if not all of the Sprinter RSN's, have happened right off the dealers lot. But being new to Sprinters, most didn't know what it was until sharing information on this forum.
Thanks for your insight.

Bruce

Mr. Pixel said:

Also, that transmission was only concerned with 100% lockup in the tallest two gears, not all gears, nor a variable bypass. So Andy's fluid relief orifice trick is clearly genius. Heck, beyond genius. But hopefully without getting into probably painful, old discussions, I still have to ask - has anybody attacked this bug by changing the fluid?

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The Sprinter's TCC is activated in ALL 5 gears via very aggressive program maps.

When activated, the Sprinter TCC is always in a slip mode with a duty cycle ranging from 5-95%.

Some owners have noticed reduced RSN as fluid ages, some with fresh fluid.

Reports of significant overfill of fluid have shown reduction of RSN which I attribute to (potentially destructive) fluid foaming resulting in a commensurate reduction of pressure and damping of the TCC spool valve circuit's fluid pressure. Doktor A

abittenbinder said:

....

Reports of significant overfill of fluid have shown reduction of RSN which I attribute to (potentially destructive) fluid foaming resulting in a commensurate reduction of pressure and damping of the TCC spool valve circuit's fluid pressure. Doktor A

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Andy,
I've wondered why overfill would affect the RSN, if you've posted the foaming theory before I must have missed it. That theory sounds better than the "the higher level changes some pressures" comments I think I've read.

I didn't say anything, but after doing your DARF modification on my 2004 I found the tranny fluid level a bit below what I calculate as the full mark and left it that way. I'm using a DIY bottoming dipstick and figuring in your 13mm correction (actually I used 1/2") so I may be off a bit. Anyway, with your DARF conversion and my transmission level mid-range the RSN has not been a problem. There has been a very occasional slightest bit of RSN at about 38 - 40 mph on the down grade of a slight incline, but a bit of throttle makes it go away immediately as we have discussed.

Based only upon my one experience, I think transmission fluid level becomes less critical after the DARF mod. That is if it was ever that critical anyway? I'm still not convinced a 1/4 - 1/2" difference of level in a sump is a problem. If it were, why do they give us a safe range? FWIW.

I'm very happy I was included in the early DARF tests or I probably would have put off doing the mod. I think that would be a mistake. vic

Just completed the DARF procedure, simply amazing. Does not even seem like the same truck. Thank you Andy.



Still patiently waiting for D.A.D (maybe bump me up a few spots for the good review?? lol)

Is there anybody who did DARF, but no changes at all, or any problems after DARFing? I'm planning to order it. Thanks

o.z. said:

Is there anybody who did DARF, but no changes at all, or any problems after DARFing? I'm planning to order it. Thanks

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Because of overly aggressive TCC (torque converter clutch) mapping in the TCM (transmission control module) it is quite unlikely that you will experience 'no changes' after performing the DARF.

As for problems, post DARF, none have been observed by me or reported to me. Rest assured, the DARF can be easily reversed with a simple procedure, if so desired.

Complete instructions and special tooling is included in the DARF kit. Still $49.99 plus shipping and handling. Simply email me at abittenbinder@yahoo.com. for payment details.

Doktor A

Hey Andy,

Just wondering if you have the part number for the plate I drilled for the DARF... I was thinking about getting one and drilling the smaller hole to see if I notice any differences.

Thanks,
Drew

Drew.eight said:

Hey Andy,

Just wondering if you have the part number for the plate I drilled for the DARF... I was thinking about getting one and drilling the smaller hole to see if I notice any differences.

Thanks,
Drew

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The plate is not listed as a spare parts number.

If you must replicate the Sprinter Global Research Center testing, just silver solder your larger orifice closed and redrill with the smaller orifice. But I forewarn you, a reset of adaptation may be necessary for accurate results. Doktor A

abittenbinder said:

The plate is not listed as a spare parts number.

If you must replicate the Sprinter Global Research Center testing, just silver solder your larger orifice closed and redrill with the smaller orifice. But I forewarn you, a reset of adaptation may be necessary for accurate results. Doktor A

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Thanks Andy, I'm not trying to replicate your testing. I drive between 1500-2000 miles a week, so fuel economy is a big deal for me. After installing the DARF I noticed a decrease in MPG. According to the paperwork that came with the DARF, I should have used the smaller drill bit for "maximum fuel economy".
I'm guessing that when I get my DAD, I will be able to reset the "adaptation". Sorry, I was not trying to offend. I guess I should have explained better in my other post.

Thanks,
Drew

does this DARF mod work on the ncv vans as well? i have had the rsn noise on downshifts since day 1. the dealer said the tranny was low on fluid and added some.

bb