After making the switch to Transynd (assume Hoot method), how often should one drain the Transynd fluid. Does it give you a longer drain interval because it is synthetic?

-Frank

Read this. http://www.allisontransmission.com/service/transynd.jsp
The numbers prove it.
Extended oil change guidelines for TranSynd™ include 50,000 miles/24 months for Severe duty and for General duty, 100,000 miles/48 months, once a 90%+ fill of TranSynd™ has been reached. (Reference Allison Service Tip #1099B for more information on how to achieve the appropriate fill of TranSynd.) Compare that to conventional transmission fluid recommended changes of 12,000 miles/6 months for severe duty. And 25,000 miles/12 months for general duty.

Frank....
If you do did indeed switch to TranSynd fluid (a TES-295 fluid) then the drain interval (assuming a 'Hoot' flush method nearing 90-95% flush) would be:
For general duty: 150,000 miles/ 240,000 kms, 4,000 hrs, or 48 months
For severe duty: 75,000 miles/ 120,000 kms, 3,000 hrs, or 36 months.
This information came from a TranSynd product manual that I got from Allison.

BHoward6.6 (http://dieselplace.com/forum/member.php?u=63361)

I just read your Allison link. Very interesting cause your numbers are different from mine.
Your numbers come from the Allison web site, mine come from a product info brochure for TranSynd/ Castrol TES-295 fluid, that list the info for the Allison 1000 series transmission, dated 2008.
I have a second 10 page "Allison" info sheet (this one is from Allison Transmissions) and it gives the same number for drain cycles as the TranSynd brochure. This one is dated 2007/10. All of my information comes from my local Allison dealer.
What gives???
:confused:

try this one. it's more along the line with your info.
http://www.allisontransmission.com/service/changeinterval/questions.jsp?model=1000&voc=HS&type=1k2k

Transmission 1000 HS
Using 100% TranSynd™ or TES 295-approved fluid Yes, The following recommendations are only valid if transmission contains 100% TranSynd™/TES 295-approved fluid.
Severe Vocation? No
Allison Transmission requires the following change intervals:
Transmission Fluid 150,000 miles
(240 000 km)
48 months
4000 hours,
whichever comes first.

Control Main (Spin-on) Filter 50,000 miles
(80 000 km)
24 months
2000 hours,
whichever comes first.

Internal Filter Overhaul

Lube/Auxiliary Filter (if present) 50,000 miles
(80 000 km)
24 months
2000 hours,
whichever comes first.