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View Poll Results: Has your transmission failed?
No Failure. Standard weight. 20 50.00%
No Failure. MH, heavy build, or regular towing. 13 32.50%
Failed within 150k miles. Standard weight. 2 5.00%
Failed within 150k miles. MH, heavy build, or regular towing. 3 7.50%
Failed 150k-300K miles. Standard weight. 1 2.50%
Failed 150k-300k miles. MH, heavy build, or regular towing. 1 2.50%
Failed 300k+ miles. Standard weight. 0 0%
Failed 300k+ miles. MH, heavy build, or regular towing. 0 0%
Voters: 40. You may not vote on this poll | Withdraw Vote

 
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Old 06-13-2019, 06:54 PM   #11
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Default Re: Has your transmission failed? When? Why?

Quote:
Originally Posted by vanski View Post
What's the difference in the torque converter for a NAG1 NCV3 transmission and NAG1 T1N tran? Can a NCV3 TC be put into a T1N NAG1?

I run at 9k lbs and up into the Sierras at least 50 times a year, well this ski season probably closer to 60 times just this winter (we're talking 8.5k vertical feet in one run).

Although these poll results aren't reflecting this failure yet, I've also heard of these failures and may try to get ahead of it.

I do drive pretty slow, but at 9k lbs, I'm sure I'm not driving slow enough....
And I live at 7000' (obviously per screen name ) so every trip in pretty much any direction starts with a descent to 2000' and every return is a pretty good climb. Twice if we are on the 17 to Phx, goes up, down through Verde Valley, then up again. The ski hill here is at 9500', 2000' of that climb in 7 miles but I'm pretty winterized and as light as a Navion can be for those 10ish trips a season. We just ran through the Sierras from Tahoe to Yosemite Valley to Kings Canyon last week, seems like you are really high but then the signs are all 6-7K, solid climbs though.

@Calbiker, how often did you or your friend change/service your trans before your failures???

I did my first flush, filter, and connector at 41K.
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Last edited by az7000'; 06-13-2019 at 07:34 PM.
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Old 06-13-2019, 07:09 PM   #12
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Default Re: Has your transmission failed? When? Why?

Quote:
Originally Posted by MillionMileSprinter View Post
So I see lots and lots of Sprinters on a weekly basis. Old and new.
My experience has been that heavily loaded vehicles that have NOT followed the forum recommended fluid and filter change every 60k (or even better a complete service) at 60k are at an almost 100% chance of failure. Properly maintained transmissions are almost always in excellent shape no matter what the miles.
Thanks, I'll be in touch for my next kits instead of my usual go to...
By complete service are you referencing this?
https://www.millionmilesprinter.com/...e-transmission
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Old 06-13-2019, 07:16 PM   #13
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Default Re: Has your transmission failed? When? Why?

Nope.. 100í and my home mountain is at 7.8kí over 120 miles and there's ups and downs... so I figure 8.5k per trip. Still hoping my 4.11 diff ratio will help me a bit. Shifts smooth as any of the many many sprinters which Iíve driven, but when those TCs go thereís really not much warning.

Iím going to do a full tranny service (I have a few service kits in stock) pre July 4th weekend..
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Old 06-13-2019, 08:34 PM   #14
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Default Re: Has your transmission failed? When? Why?

Most failures appear to be motorhomes. Most pushing 11k lbs 24/7, some towing a car, with gcwr over 14k lbs. What appears to happen is high absolute engine output puts part of the TC in the fatigue failure regime. around 75% of the steels yield strength. In this range a few million or 500k cycles causes crack formation. Thus part of the turbine or stator vane breaks. This causes ancillary damage. Quickly resulting in no drive, or a trans filled with debris.

Thus the cycles are cumulative. In aerospace these are called life limited parts. Parts that under a certain stress regime, will begin to fail within a certain cycle count. The solution is to avoid adding these cycles when possible. Avoid running continuously at throttle over 80%, and keep under 70% sustained. A higher gear isn't your enemy.

The ncv3 tc is physically larger. I don't think it will fit in the T1N bell housing.
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Old 06-13-2019, 08:48 PM   #15
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Default Re: Has your transmission failed? When? Why?

Some quick math.
100,000 miles at 55mph is 1800 hours.

1% of those hours ay 100% throttle is 18 hours.

4000 rpm times about 50 stator vanes. Each vane gets a cycle, so 50x4000 is 200,000 cycles per minute.

Times 18 hours times 60 time 200000 equals 200,000,000 cycles.

Lots of room for failure. But only if you cross into the fatigue zone. Under the endurance limit, it doesn't happen.
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Last edited by Midwestdrifter; 06-14-2019 at 01:46 AM.
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Old 06-14-2019, 01:50 AM   #16
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Default Re: Has your transmission failed? When? Why?

Quote:
Originally Posted by DRTDEVL View Post
And how many of them changed the fluid (approved only), filter, electrical connector and cleaned the shift solenoids every 50,000 miles?

My point was its all about proper service.
The poll doesnít have a service history for every failure unit, but a couple were serviced at 40K and 80K and still failed prematurely. There are too many variables to nail it down to one cause, but the common denominator in these failures that far exceeds T1N vans, is that these motorhomes are running at 10K lbs. to 15K lbs 100% of the time.

Gary
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Old 06-14-2019, 02:04 AM   #17
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Default Re: Has your transmission failed? When? Why?

And, it depends quitre a bit on HOW the heavier than normal RV conversions and those towing heavy, high wind resistance, trailers are driven.
Are they manually downshifted to 4th gear to get out of 0.83: 1 Overdrive or do you leave the transmission in 5th gear overdrive and run very high % engine load (which wastes a ton of fuel).
If they aren't gearing down when the % engine load exceeds 80-85 % for longer periods of time (yes, time is a big factor here) they are needlessly stressing the torque convertor and transmission, plus over-fueling the engine significantly.
Do they understand that a T1N (OM-612 or OM-647) actually gets significantly better fuel mileage in the 2600-3100 RPM range in 4th gear than it will get running @ high % engine Load in 5th gear. at < 2500 RPM.
Many have tried this and most seem to agree, engine and trans run cooler, better performance, better fuel mileage at the lower % Load higher RPM. decreased GPM in 4th gear (or even 3rd gear if you need it and slow down to an appropriate speed.).
If you hammer your engine and transmission @ nearly 100% of their capacity.....how long do you think they will last?
Be proactive, manually downshift when needed and your rig will spend SO much less time @ or near 100%.
Hope this helps,
Roger
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Old 06-14-2019, 04:35 AM   #18
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Default Re: Has your transmission failed? When? Why?

Gearing down could be part of the problem!

Failures increase with rpm squared.

The issue more than likely is metal fatigue. The T1N tc is undersized for heavy MHs. This comes from the company that rebuilds tc for Silverstar.

This failure has absolutely nothing to do with servicing. I change fluids (inc tc) every 40k.

BTW, the NCV3 tc contains clutch torsion springs. T1N does not. The springs will relieve some stress.
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Old 06-14-2019, 10:06 AM   #19
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Default Re: Has your transmission failed? When? Why?

Yep. For all we know, full load downshifts may actually add fatigue cycles. That may be why the tcm refuses to downshift sometimes? Hard to say.
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Old 06-14-2019, 02:52 PM   #20
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Default Re: Has your transmission failed? When? Why?

I find that if I downshift early for a known steep grade or other reason, the shifting will be much smoother. Looking ahead and anticipating/planning your moves has some benefit.

vic
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