Diesel Place banner
1 - 3 of 3 Posts

· Registered
Joined
·
26 Posts
I followed this procedure to a T last weekend when changing from Dex3 to Transynd. I was a little nervous. I am very mechanically capable, but have never flushed a tranny before. Doing major work on soemthing 20 years old and worth a couple grand is one thing. Screwing with something worth $40k and less than a year old is another story as far as comfort goes!


Anyway, worked great. Really took my time cleaning everything real good and took me about 2 hours. I got a 5 gallon drum of Transynd. One thing that added time was setting up containers into which to transfer the fluid. I used some OLD Sunny D OJ containers. Measured out and marked exactly 1 qt and 2 qts on the containers. Transferred the fluid from the 5 gallong container to these to pour into the dipstick. This helped me know exactly what was going in. I then used some old Rotella T gallon containers to measure what had been removed and emptied into my drain pain.


I did not replace my tranny pan. The guy at the allison dealership said that he did not believe the extra capacity (as little as it is) was worth the money. According to him, if you want to reduce the heat in the tranny, you would be better off adding a second cooler with a bypass valve for winter time than getting the deeper pan. If you are NOT replacing the pan, it is still imperative to drop it. Due to the indention of the drain plug, there is quite a bit of fluid that gets trapped in the pan that will never drain. In addition, for a true flush, you must change the internal filter.


As far as how fast the fluid drains, that can vary. It would REALLY be better to get someone to start it up for you, even if it is a neighbor or soemone. Won't take more than 5 minutes of their time. If you r truck has been sitting for a while, it could take a bit. I started my project of draining and dropping the pan. But I had to stop to go to my setpson's basketball game before I had the chance to reassemble and start the flush procedure. Truck had been sitting ivernight in the driveway. Fluid had been drained from the pan for about 4 hours. When the engine was first started, it took 20 seconds or so before it started flowing out of the cooler line. Once it did, it came at a pretty good clip. Also note that AFTER the engine is STOPPED, fluid will continue to drain for a couple of seconds. So if you are getting close to the top of your container, stop with a decent cushion.


Other than that, it was a simple process. Be sure to cycle the gears when doing the final cold check to fill up all the hydraulics of the tranny. I failed to do this and was a lot lower than I should have been when doing a warm check. Luckily I got it much closer and was able to just top it off during the hot check.


Oh yeah, it was nice having the extra Transynd to go ahead and replace the fluid in the tcase (very easy) and have 2 qts left over for pre-filling the spin on filter at later changes.


I also took the opportunity to swap in Mobil 1 75W-90 in both pumpkins. Its nice to know I don't have to touch a fluid other than motor oil in this rig for a LONG, LONG time!
 

· Registered
Joined
·
26 Posts
TClark said:
ok, being a newb to this forum AND to the Dmax/Ally club, im looking at almost 20K in mileage on my 03 2500. Is it time for a trans. fluid/filter change, and what is this transynd stuff???

First off, it is recommended by GM and Allison that you change the internal filter and fluid in the tranny at or around 25k miles. The GM fluid is Dexron 3, the latest version of the same tranny fluid GM has been using for decades.


Transynd is a synthetic fluid that is recommended by Allison. As a matter of fact, with "normal" use, you can go for 100k miles on Transynd without another fluid change. The fluid is compatible with Dex3, so you can mic them, but the 100k deal isn't valid until you have at least 90% saturation of Transynd. Your tranny pan holds around 7.5 qts, yet the entire system holds around 12.5 qts (cooler, lines, torque converter). So simply draining the pain and refilling with Transynd will not get you to the 90% level. It will take several fluid changes before this occurs.


Hence, many use the flush methid described above to "completely" flush the old Dex3 out of the transmission's hydraulic system. It is a fast way to achieve the 90% level. From talking with the Allison rep, he also states I should see about a 15-20* temp drop by using Transynd over Dex3.


Transynd is usually only available from your Allison dealer and runs around $30 or so a gallon.
 

· Registered
Joined
·
26 Posts
dmaxalliTech said:
Sparky, side note on your comment on the deep pan...
I have to agree your likely not gonna notice anything when switching to it, but I feel that the extra capacity is peace of mind... More oil the better in my opinion. Since your already buying a filter anyways, the only additional cost is the pan it self and you already will have the old pan off....

I do agree with you. I have always run deep, finned pans on my 700s. I just didn't want anyone to think that (a) you had to get the deeper pan for use with Transynd or that (b) you would see any major difference in the deep versus stock pans regarding performance.


But, note to everyone, if you do get the deeper pan DON'T FORGET THE DEEPER FILTER/PICKUP. Had a friend one time that ran a deep pan on his 700 with a stock filter. Needless to say he thought he had plenty of fluid still in the pan when he was runnign low one time, and actually he did. But he wasn't sucking any into the tranny!!
 
1 - 3 of 3 Posts
Top