I have just over 116,000 miles on our '02 3500 D/A ... it came with Dextron which I have changed every 25,000 miles ... so far as I can tell, her Allison tranny is in excellent condition ... I am wondering how complicated it would be to convert to synthetic fluid? ... do I need to have the Allison completely flushed or can I drain it as normal and start adding synthetic which will be mixed at first but become purer as time goes on ... would I need to change the inside filters ? ... what would I really gain from making such a change? ... tips and comments from folks who have made this change would be appreciated

Jim

Jim,

Allison Transynd is 100% compatable with Dex III. After 3 routine changes (drain the pan and change the filter) you will have approx. 93% syn and can then extend the drain intervals to 100,000 miles according to Allison. I did this on the 01 at each 25,000 miles and then sold it at ~80K. Never did notice any change in temp or operation.

I changed the fluid once on the 04 with Transynd, then took it to Mike for a SCIV and have Dex III since then.

BTW, have been checking out the Escalades. Very nice.

I think the first thing that comes to my mind is "if it isn't broke why fix it"......

I Changed to synthetic tranny fluid using the method in the thread below. The only changes I made to it were using a clear hose that you can get at most hardware / home improvment centers. I also got the hose about 5-6 ft long so I could place my bucket off to the side of the vehicle. My truck is not lifted so it was just easier for me to see it off to the drivers side. I got six gallons of Mobil1 which cost me about 120-130 dollars. So you can see there is a big cost difference between Dex and a Synthetic. I had a 5 gallon bucket which I marked with a ruler so I could better judge how much came out. You can read the thread but basically you disconnect the return line from the cooler and run it into the bucket. Someone else starts the truck which pumps the fluid into the bucket while you pour in fresh fluid through the dip stick tube. As you can imagine - you don't what to be trying to do this out of a five gallon bucket of fluid. It was tuff to do with quarts. I would suggest that what ever you use, you put in a clean 1 gallon container first so its easy to handle and pour into your funnel. It went smooth enough though I had my wife do the start and stop part and had her watch the bucket and tell me what mark it was at, while I tried to keep up. The tuffest part for me was pulling the return line and putting it back. After you pull the keeper it has to come out maybe around 1/2 inch or so to clear the tranny. I had just enough clearence to make it but I had to work it.

All that said yes you can just drain and replace and after two or three times you're up to some really high percentage of synthetic (high 90's). They say you only have to replace the internal at an overhaul, but I think it never hurts to wipe the gunk out of the pan. The pan gasket is re-usable unless damaged and Eric (in my sig) has the filters etc.....

See post 14 on page 2 for the proceedure. If you have any question don't hesitate to ask.....Bill

http://dieselplace.com/forum/showthread.php?t=22403&highlight=tranny+flush


PS FWIW I got the clear hose in the size listed in the thread. Maybe the clear hose isn't as streachy or maybe it was the tranny fluid on my hands but it was difficult to get the hose past the bead on the return line. I put a tie wrap around it to keep it secured, which seemed to work

Changed mine to Transynd about a month ago via the drain plug method (7.4 quarts plus a bit for the new spin on filter)...if you drop the pan, you'll get a bit more out but not worth the extra work IMO. Transynd is 100% compatible with Dex III.

Allison site says to change it every 50,000 miles (or 25K if severe duty) or 2 years, whichever comes first. After the second change, the fluid is diluted enough to go with synthetic to go with a 96,000 miles or 4 year, whichever comes first, schedule.

Allison also says to change the internal filter only if you're doing an overhaul. The spin on does most of the work so change it regularly.

Alternatively, there's the "hoots" method (do a search for the thread) of dropping one of the transmission cooler lines (from cooler to transmission) and use the tranny's pump to drain all the tranny fluid. Easier if you attach some tubing to the cooler and into a bucket and have a buddy outside telling you when to turn off the engine when the fluid is emptied.

GM/Allison doesn't recommend flushing machines, just changing the fluid. Flushing machines can damage your tranny although some members have used a flush machine with no problems....risk is up to you.

I just use the drain plug method and mix the Transynd with DexIII 'cause it's easy with no mess...can't be bad if Allison recommends it.

just got off the phone with the service manager at the local Allison transmission sales/repair facility ... gave him the info on our truck as outlined in the first post in this thread ... he advised against converting to synthetic unless the transmission someday has to be rebuilt ... thought that was interesting

Jim

Yes, interesting considering Allison's website promotes Transynd as a synthetic ATF "developed by Castrol and specillay engineered for Allison Trnasmission. It's specifically designed to make Allison Automatic-equipped vehicles even more efficient, more productive and more profitable to operate". If I can extend my service intervals and still protect my tranny, it's a good thing.

Would be curious as to the reason from the service manager as to why not to convert to synthetic.

Allison does not like Dex 3 in their transmission. Dex 3 was GMs idea.

i have run dex 3 for 160000 miles and replaced with a suncoast 5.the cluthes in my old tranny looked very good.you could still see the writing on them.i would not change it

Dex 3 does a good job. Synthetic does an excelent job.

JEBAR
In medium duty trucks like freightliner and international, the allison TRV 3000 autos come from the factory with synthetic already in them.