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Dextron VI fluid use

SFC Cobb

SFC Cobb

Jesus Freak
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Hurst, TX
I was looking on DP about the use of Dextron VI in 03 Allison trans. Some of the posts and a link to an Allison service bulletin made me believe that it is not OK to use Dextron VI in the earlier trans.

One thread says that two seals in the trans (shaft output and one other seal) will harden with the use of Dextron VI and can start leaking.

I am not positive but I think I put Dextron VI in my trans when I changed the fluid a while back. I have had a leak that looked like it was coming from the weap hole at the trans and engine mount flange (bell housing). I thought it was coolant but it also bears a strong resemblance to trans fluid.

This info is beginning to make me wonder about the source. Funny thing is after all the leak spots it has stopped leaking for now.

Is the Dextron backwards compatible? Would there be a problem if I were to change to syn. fluid?

What do you think it cost if I was to go to an Allison dealer and have the trans overhauled. I suspect that I may have some clutches slipping.
 
Would there be a problem if I were to change to syn. fluid?
Click to expand...

Tom, at this point, its only gonna help you out. And I wouldnt bring it anywhere until it fails. If it aint broke, fix it.
 
I am not going to do anything right now, just curious about what it would cost for and Allison repair or overhaul vs me and my son tackling it.

Is the fluid backward compatible?
 
What about this part of my post above. Is the Dextron VI causing this problem. I understand that the fluid has to be compatible with Viton seals. This makes me think these seal are made of something that is not compatible with the material these two seals are made from. I would appreciate any info about this.

One thread says that two seals in the trans (shaft output and one other seal) will harden with the use of Dextron VI and can start leaking.
 
SFC Cobb said:
What about this part of my post above. Is the Dextron VI causing this problem. I understand that the fluid has to be compatible with Viton seals. This makes me think these seal are made of something that is not compatible with the material these two seals are made from. I would appreciate any info about this.

One thread says that two seals in the trans (shaft output and one other seal) will harden with the use of Dextron VI and can start leaking.
Click to expand...

Dex VI is backward compatible according to GM, the license owner. Yes with Dex VI there can be an issue with Viton seals, according to Mike at Inglewood and Allison.

To be clear, Amsoil Torque Drive, and Universal ATF are both Viton compatible, if you are running a stock trans, '05 or older I recommend Torque Drive, '06 or newer Amsoil Universal ATF. If you have a built trans of whatever year I recommend Torque Drive due to the higher holding pressures required, remember your warranty is no longer in effect once you modify the Ally.

Hope this helps.
 
I have an 03 with 276.000 miles. This is why I am questioning a lot of this stuff. Making changes in equipment with that many miles is always a potential for issues. Thanks.
 
i havent seen any issues of leaks as of now, we do plenty of trans stuff. not to say in a bunch more miles it cant happen. the stuff hasnt been out for to long and maybe nothing has shown up yet here.
 
My leak came back today. It had not leaked for ove 3 weeks and I go out this morning and under the truck was fluid of some kind from the same place as before. I am really thinking about pulling the trans and see if it is a cracked block or freeze plug or something else on the block. Also a check of the input shaft seal. While I have it out I will go ahead and replace the clutch packs, etc.

This has really got me puzzled.
 
One thing to note: If your trans is over the cutoff S/N for the Dex VI compatable seals, that does not mean it actually has those seals. I just finished rebuilding my trans, and while I had it apart, I replaced all the thrust bearings (all but one felt gritty). Several of them where updated along the way, and my S/N was well over the cutoff, but it had the old bearings. Just FYI.
 
My truck is an 03 and has to be before the cutoff sn. I would say the seals are not compatible.

I went to an Allision repair facility a few days ago and they pulled the inspection plate on the bell housing and said it was dry in there. They said that is is very rare for the front seal to ever leak on these trans.

That is good news for me because that says it has to be a coolant leak from somewhere outside the bell housing. It almost has to be in the rear corner of the left head area. It is very difficult to see up there.

The leak is still not an eveyday occurrance. Days when the temp is in the 30's at night is when it seems to leak. I think I will go get some Dexcool tabs and put them in it and go from there.
 
I had something similar with my car way back before I did the engine swap and replaced the radiator with an all-aluminum Cobra radiator; The Passenger side tank end would leak, but only when it was REAL cold out and the car was sitting for a while. Wonder if there's any joint that could leak like that near the back of the engine. Could it be a freeze plug?

BTW, I was just throwing that caution out for everyone's consumption as an FYI, primarily for those that are considering using Dex-VI and see that their S/N is over the "Cutoff number".

SFC Cobb said:
My truck is an 03 and has to be before the cutoff sn. I would say the seals are not compatible.

I went to an Allision repair facility a few days ago and they pulled the inspection plate on the bell housing and said it was dry in there. They said that is is very rare for the front seal to ever leak on these trans.

That is good news for me because that says it has to be a coolant leak from somewhere outside the bell housing. It almost has to be in the rear corner of the left head area. It is very difficult to see up there.

The leak is still not an eveyday occurrance. Days when the temp is in the 30's at night is when it seems to leak. I think I will go get some Dexcool tabs and put them in it and go from there.
Click to expand...
 
I am not sure about a freeze plug in that area although the end of the head is usually where they are. I am thinking about taking the truck in for a cold pressure test of the system. If the head gasket is leaking hopefully it will be a warranty repair since they replaced both gaskets back in Sept-Oct 08 time frame.
 
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