Transynd or Dexron VI?

Depending on the year it came with either dexIII or dexVI. My dealership had never even heard of Transynd when I had them replace the trans. cooler lines. Luckily they were cool and bought some Transynd just for my truck to top off the trans. after the line replacement.:)

Pickups have always used Dexron. The Medium Duty trucks 5500/6500 use TranSynd.

Dex6 has been used in pickup builds since Jan, 2007. Basically, if you have a new body style GMT900, it was factory filled with 100% Dex6.

I believe they started using Dextron 6 in the '05 or '06's.

The manual in my 06 says to use Dex IV

The manuals and even the dipstick can be wrong.

My '06 says DEX VI in the manual and on the dipstick, but it was made before the cutoff, so I should only run DEX III based, TES-389 or 295 fluids.

I have a classic model 06, should I use DexIII?

It will before the S/N cutoff and not have the DEX6 compatible seals. (DEX6 causes hardening of common types of Viton)

Use a DEX3 (D3/Merc) with TES-389 rating for seal compatibility or better, use a TES-295 DEX3 synthetic.

Where can I get info on SN cutoff?

Pickups have always used Dexron. The Medium Duty trucks 5500/6500 use TranSynd.

Dex6 has been used in pickup builds since Jan, 2007. Basically, if you have a new body style GMT900, it was factory filled with 100% Dex6.

TranSynd is an option on the MD trucks (RPO-MBT), but not standard. It is not offered on the LD trucks. An Engineering contact I have at Allison told me that all of the 1000 LCT transmissions are shipped out of their factory with Dex 3 in them. GM then tops off the transmissions with Dex 6 when the LD vehicles are built and as they were instrumental in the Dex 6 development, they require it as part of their warranty. Dex 6 is completely compatible with Dex 3 so you should see no problems with mixing it, other than meeting GM's warranty requirements.

I have a classic model 06, should I use DexIII?

Use a TES-295 rated oil and be done with it. Amsoil, Transynd, M1 and a few others that are TES-295 rated will work just fine. TES-295 is still the best fluid to put in your Allison.

Well the guy I bought my truck from said he used DexIV fluid when topping off after filter change.

I just want to make sure I am not killing the tranny!

Can I change the fluid with Transynd myself? How hard is it, I know the tranny has a drain plug.

Well the guy I bought my truck from said he used DexIV fluid when topping off after filter change.

I just want to make sure I am not killing the tranny!

Can I change the fluid with Transynd myself? How hard is it, I know the tranny has a drain plug.

Its super easy. Just as easy as doing an oil change on any car.

When draining the pan and changing spin on filter, how much is required to add? I am gonna go to Ali dealer tomorrow and get fluid.

When draining the pan and changing spin on filter, how much is required to add? I am gonna go to Ali dealer tomorrow and get fluid.

Buy 2 gallons. That will do the job......unless you plan on doing your transfer case then buy 3 gallons.

I do not have a transfer case, Please PM me I need tranny fluid and rear end fluid for my 06 I just bought. I would also like some grease for the zerks.....

I do not have a transfer case, Please PM me I need tranny fluid and rear end fluid for my 06 I just bought. I would also like some grease for the zerks.....

PM coming your way!

Remember, there is no Dextron IV, or 4, only Dextron III and Dextron VI, 3 or 6...

TranSynd is an option on the MD trucks (RPO-MBT), but not standard. It is not offered on the LD trucks. An Engineering contact I have at Allison told me that all of the 1000 LCT transmissions are shipped out of their factory with Dex 3 in them. GM then tops off the transmissions with Dex 6 when the LD vehicles are built and as they were instrumental in the Dex 6 development, they require it as part of their warranty. Dex 6 is completely compatible with Dex 3 so you should see no problems with mixing it, other than meeting GM's warranty requirements.


The new DEX6 compatible seals started with S/N 6320784373 for Baltimore built (pickup) transmissions. This basically coincides with the 2007 "Classic" pickups.

The mix of DEX3 and 6 you describe only occured with the 2006 and 2007 "Classic" pickups. It ended with the expiration of the licensing for DEX3 Dec. 31, 2006. After that, all the factory fill was going to be 100% DEX6. (This basically coincides with the "New body" 2007 trucks). This is fine, since the new seals went into production about 6 months before.