Fluid recommendation for Allison HT740

[Creekside]

I recently purchased this ex-USPS Mack tractor. There has been no maintenance done since 2007ish as far as I can tell. I want to do a service(maybe a couple) on the transmission. There's no current indication of a problem.

What would you recommend? It currently has something red in it that does smell like ATF and has an old sticker on the frame that appears to read "USE MOBIL 1 SYN" next to the transmission filler.

I plan to use the truck under a dump trailer in the 54,000-66,000 gross weight range. I'm thinking based on the fluid recommendations that a C-3 oil might be a little more robust. The lowest temp allowable for a C-3 lubricant is 32*F and I don't expect to run the truck colder than that. The gravel piles will likely be frozen anyway.

 

[64bawagon]

We always ran Dex 3 in ours and never had any issues. We had at least 5 of them.

 

[redhat]

I think I’d seek out a synthetic Dex III like a Mobil 1 ATF or a TES-295 like Mobil Delvac 1 ATF. I don’t think I’d put a LV fluid like MaxLife or Dex VI in it.

I believe C3 and C4 oils this trans could’ve also been ran on 15W-40s with the aforementioned specs.

 

[jetman]

I recently purchased this ex-USPS Mack tractor. There has been no maintenance done since 2007ish as far as I can tell. I want to do a service(maybe a couple) on the transmission. There's no current indication of a problem.

What would you recommend? It currently has something red in it that does smell like ATF and has an old sticker on the frame that appears to read "USE MOBIL 1 SYN" next to the transmission filler.

I plan to use the truck under a dump trailer in the 54,000-66,000 gross weight range. I'm thinking based on the fluid recommendations that a C-3 oil might be a little more robust. The lowest temp allowable for a C-3 lubricant is 32*F and I don't expect to run the truck colder than that. The gravel piles will likely be frozen anyway.

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View attachment 212245

Call Tom Johnson, ext.# 2, at JG Lubricant Services. He's a retired Allison/GM fluid engineer.
https://jglubricantservices.com/contact.html

 

[dfarr67]

I've been looking for a fluid myself, in the TES 295/668 range I found the Chevron syn ATF HD to be better priced.

 

[nascarnation]

That's a fine looking old girl! If it's not getting real hot (over 230f sump), any old Dex III or 30W engine oil will work just fine. If the fluid looks pretty red and the rig runs fine, maybe no need to change it at all. How many miles do you expect to get on this truck?

 

[Creekside]

That's a fine looking old girl! If it's not getting real hot (over 230f sump), any old Dex III or 30W engine oil will work just fine. If the fluid looks pretty red and the rig runs fine, maybe no need to change it at all. How many miles do you expect to get on this truck?

I know it has spent much of the last 17 or so years sitting, enough that the wheel hubs drew enough moisture to rust the bearings up pretty good. I’d feel much better if it was changed with what I’m seeing elsewhere. Fluid is cheaper than a transmission R&R.

A long day is 250-300 miles on the dump truck although lately they’re substantially less. I’m hoping it stays busy enough to work at least a couple days a week. So figure 500-600 miles a week.