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Discussion Starter #1
I have a 2002 Chevy Duramax/Allison with 28K miles. I purchased this new and only use it to pull my 5th wheel and short trips in town. I want to service the Allison Transmission and my question is does any one recommend any certain fluids besides the Dexron III. What about the Syn Fluids, any real advantages? I would like to to the service myself, any suggestions?

Also I have been trying to get more info regarding the tire size. I have upgraded to the larger 285's size tire but now I am reading that this may cause problems when towing. Has anyone heard of this issue? I know that the factory tires are 245's and I have heard about upgrading to 265's. I do not have any problems with clearance with the 285's.
 

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285s are fine. They do mess up your speedo a bit and will eat some power in your low end.

As far as fluid - Torque Drive syn fluid from Amsoil is what many here run. That or Transynd or Citgo Quatrasyn which are also highly regarded.

Transynd is the standard but the others are solid choices. Much better to use syn than dex.
 

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jm6546;1589902; said:
I have a 2002 Chevy Duramax/Allison with 28K miles. I purchased this new and only use it to pull my 5th wheel and short trips in town. I want to service the Allison Transmission and my question is does any one recommend any certain fluids besides the Dexron III. What about the Syn Fluids, any real advantages? I would like to to the service myself, any suggestions?

Also I have been trying to get more info regarding the tire size. I have upgraded to the larger 285's size tire but now I am reading that this may cause problems when towing. Has anyone heard of this issue? I know that the factory tires are 245's and I have heard about upgrading to 265's. I do not have any problems with clearance with the 285's.

I have a 03 Dmax with 24k miles and use it 90% for towing our 8,200lbs 5th, I have changed the fluid twice now and have just used the regular Dex III, if I were pulling much higher weight I would consider the Syn fluid.

The Syn fluid is also three times the cost...if you change you fluid on a regular basis, tow a 5th well under the max rated tow rating, I think reg Dex III will be fine.

I used Syn fluid in my GN...but I also hold 10-15lbs boost for many seconds every time I run the 1/4 mile...so I build lots of heat.

I also upgraded tires to 265's size...seems to be fine for pulling, didn't want bigger tires than 265's truck already sits higher than 5th, and without spending big $$$ the 5th is as high as I can go (equalizer changed , axles flipped, spring extensions now illegal to do)

265's will change mph and gear ratio 3.9% / 285's - 7.9%
 

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BTW - if you do some searching and reading in the Allison areas of this board - you will find more info than you'd imagine regarding servicing, fluids, filters, etc.
 

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Discussion Starter #6
Thanks for all the info, what are the advantages to the Syn Fluid over the standard Dexron III? Checked with local Allison Dealer and Transyn is $34 per gallon. I am not really worrying about the cost that much if its really worth it. Just don't want to be throwing money down the drain if not needed.

Also has anyone experienced the Tranny running hot on hard climbs. I had a Hypertech programmer that I have used, it has great power and gobs of torque but seems to be a bit to much when towing. I worry about tearing something out.
 

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jm6546;1591044; said:
Thanks for all the info, what are the advantages to the Syn Fluid over the standard Dexron III? Checked with local Allison Dealer and Transyn is $34 per gallon. I am not really worrying about the cost that much if its really worth it. Just don't want to be throwing money down the drain if not needed.

Also has anyone experienced the Tranny running hot on hard climbs. I had a Hypertech programmer that I have used, it has great power and gobs of torque but seems to be a bit to much when towing. I worry about tearing something out.

What kind of weight do you tow ??

Burnt fluid is a problem.....Syn fluid will help protect better against the extreme heat, but regular fluid changes and reasonable weight towing should be fine for Dex III

My 5th is 8,200lbs and high Tranny temp has never been a problem for me even on our big BC hills. I also use a programmer (level #1 & #2 only for towing) and have not seen a difference in T. temp's over stock tunes.

If you tow normal loads, change the T.fluid often...I don't see the advantage of using Syn fluid.

My daily driver Astro now has over 310,000kms and has been driven hard all it's life including towing to max ratings for 6 years of it's life...it has had regular T fluid & filter changes and still runs the original Tranny...and never used Syn fluid.
 

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Running syn will help your tranny hold more power and run cooler. It is the safest bet by far and well worth the $$ IMO. If you change your spin-on about every oil change (7K) and change your pan filter every third time or so (21K) you will not need to do a major tranny service. You can ease into the syn fluid by just refilling with syn after you drop the pan or you can change it all out and start fresh.

Read up. Do some searching. Especially find posts/threads by Mike L. on the topic - he is one of the most knowledgable Allison guys around. Go to the tranny sections of this site (here and the aftermarket). There you will find your answers and more.

I run Torque Drive in my Suncoast built trans.

If your tranny is getting hot - you can add a larger trans cooler. Contact Mike L. as he is the one that designed it and sells it too.

Not sure about your hypertech as I never had one but you should note that you can hurt your tranny with too much power. You also might want to get a 4" or 5" exhaust to keep your EGTs down with the tuner. Or else you can melt your turbo on those hard climbs while towing. Can also overboost it and rip it apart regardless of the EGTs. Get a good mech boost gauge and pyrometer! Keep boost below 30 and pyro to 1200 or so and you'll be safe.

Again - congrats on getting a d-max - you now have lots of reading to do to understand how to upgrade and maintain your engine and trans.
 

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Discussion Starter #9
I just purchased a Keystone Everest 295T which weighs in at 10,510. Before I was pulling a Keystone Cougar at about 8200 pounds. I have not taken a trip yet with the new rig so that is why I am curious about the tranny. I take about two long distance trips per year that average about 2500 miles each. Most of the other trips are maybe 6 that are only a few hundred miles each. What would be considered that average mileage for changing the tranny fluid? The dealer gave me 30K miles on average service.
 

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I change my fluid every 20kms (or 15k miles) which for me is every two years. 30k miles may be on the long side if you really want to keep the fluid fresh.

I change the external T.Filter every 5kms same time as I change the oil, its cheap & easy to do so.

Your 5th combo sounds like my good friend, that has a 2002 Dmax towing a 10,000lb 29ft 5th, he just returned from a 8k trip to Mexico and back with no problems.

All in all syn fluid is great stuff...but for my towing / usuage needs I prefer to do very regular service and use the Dex III
 

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Discussion Starter #11
Another question, what about the deep transmission pans, do they offer any real advantages? Would they help in keeping the transmission cooler? Any suggestions on brands?
 

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I think the deep pans do offer an added benefit for cooling, they sure do allow you to run more fluid which would help lower temps.

I've always been a in-front big as you can fit T.cooler guy.

My Astro & GN both have 18,000gvw RV coolers..and have worked for me for years...

In my truck I just make sure that the cooler is as bug free as possible..I take my high pressure water hose to it monthly...you would be surprized what comes out !!
 

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An 02 w/ 28k mi on it? You have a nice truck (of course you know that).
WHat I learned from Allison, and here, persuaded me to change over to Transynd. Allison's reccomeded change intervals on Transynd are outrageous, I believe 75,000mi severe duty, 150,000mi light duty. They also warranty their transmissions for 100k mi in other applications w/ the switch to Transynd when new. Those 2 things sold me on using it.
Would also lengthen your change interval, even being ultra cautious like you are w/ changing your fluid.
 
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