10 speed... ulv or thicker?

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Dec 2, 2025
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I'm sure some of you guys have switched from ulv fluids to something with a higher viscosity. I personally have a 10l1000 and I'm trying to decide if I want to keep using ulv or switch to something thicker. Currently using valvoline ulv but thinking about maybe valvoline Maxlife or their Extended Protection. Any of you guys have experience with my application? Or just in general positive or negative between ulv vs. Something thicker.
 
Yep, stick with frequent changes of ULV and if you feel like it, the appropriate dose of Lubegard Platinum.

Valve bodies are the weak link in all of the 10 speeds. You don't want to risk them getting dirty and worn, and you don't want to slow down their actuation in any way.

Some people use a slightly thicker fluid and get away with it, but others have reported terrible shifting. It is too much of a crapshoot with too many expensive parts in my opinion.
 
If I remember someone is running hpl Green in their 10 speed and they're not having issues and someone else is running a thicker fluid too but I can't remember what it was but he claimed that it fixed the odd shifts. the new Valvoline restore and protect has the same viscosity as the Valvoline MaxLife and Valvoline Extended Protection but claims ulv and I wonder if the other two will get updated as well. Another member has a Mercedes 9-speed which specifies uov fluid which if I'm not mistaken is even thinner than the ulv that Ford and GM use and had no issues with Max life in that 9 speed.
 
Transmissions are different then engines when considering going thicker. Most every engine that is spec'd say 0w/20 can use say 5w/30 with out issue and many were designed with 5w/30 and later moved to 0w/20 simply for EPA goals. So going thicker in these cases is good in my opinion. Transmissions, however, are designed from the start for a certain fluid and the viscosity is important. For that reason I do not recommend deviating from the OEM spec viscosity or type of fluid. Use what it came with and spec's for.
 
Just use what the manufacturer recommends. Transmissions are not that rough on fluids, there's no reason to look for something thicker.
There might be in some instances, but generally this is a sound approach-- use OEM fluid, keep it cool and keep it fairly fresh (25k-30k drains).


Many modern failures are attributable to "lifetime" fluids being left in too long. The other failures tend to be design flaws that even frequent service would not prevent.
 
I'd get a better valve body in there. Viscosity (change) isn't going to prolong anything or fix defective hard parts.
 
Thanks everybody for the replies. I currently don't have any concerns with the way the transmission operates but I know these 10l1000 are a problem child for GM. There are some well known 10 speed transmission builders that don't like ulv and use a dex6 or equivalent and don't have any problems but there are also some that don't have a problem with running ulv 🤷🏻‍♂️ as it with most things ask 10 different people you'll get 10 different answers lol. I'll probably have a warm fuzzy feeling putting in a thicker oil....and then go for the first test drive and the first shift slams into gear because it's too thick (I know my luck lol).
 
I attempted 50% amsoil LV in the ford 10R80, which is a ULV unit. Amsoil said it would work. I observed the same thing I did when a dealer put a thicker, universal BG fluid in a aisin-Warner transmissionmission. There was a longer gap during the gear change and it slapped a little bit harder into gear. On one hand it felt firmer, which would seem good, but after driving it really it just felt clumsier, “blockier.”

I put the right low viz fluid into the AW transmission and it was a huge improvement.

For the 10R80, I put ULV back in, resulting in a ratio of 1/4 LV and 3/4 ULV. That was close enough, and with lubeguard red my problems were solved for the moment so I stopped messing with it.

Bottom line, viscosity changes mess with the finer points of shift timing. Don’t mess with that in broad strokes unless addressing a specific issue.

Edit: not dogging amsoil, they are my goto atf.
 
Based on?
According to their product information, they are recommending it for ULV use. I find that interesting since it is somewhat thicker than a true ULV.

Keeping the valve bodies clean is the aim of the game, but Valvoline Restore and Protect is designed for deposits, and it isn't really deposits causing the problems, it is dirty fluid causing valve body wear in most cases. Not sure the Valvoline Restore and Protect technology will do much for that.
 
According to their product information, they are recommending it for ULV use. I find that interesting since it is somewhat thicker than a true ULV.

Keeping the valve bodies clean is the aim of the game, but Valvoline Restore and Protect is designed for deposits, and it isn't really deposits causing the problems, it is dirty fluid causing valve body wear in most cases. Not sure the Valvoline Restore and Protect technology will do much for that.
I can't remember what post I saw the numbers in, but (and my memory may be wrong), it was around a full 20% thicker than ULV numbers. I remember thinking "that's a lot, not in my 10r60".

I still don't know why the person I responded to thinks that transmission is a candidate for it. OP didn't mention issues, is it just the consensus that the Valvo is the 'best' and that his transmission with unknown mileage needs it?
 
Thanks everybody for the replies. I currently don't have any concerns with the way the transmission operates but I know these 10l1000 are a problem child for GM. There are some well known 10 speed transmission builders that don't like ulv and use a dex6 or equivalent and don't have any problems but there are also some that don't have a problem with running ulv 🤷🏻‍♂️ as it with most things ask 10 different people you'll get 10 different answers lol. I'll probably have a warm fuzzy feeling putting in a thicker oil....and then go for the first test drive and the first shift slams into gear because it's too thick (I know my luck lol).
Yeah, enough of a problem Allison pulled licensing and forced dealers to walk out to existing vehicles and pull the badging (although I chuckle as I wonder how many actually complied)

If I had one and I wanted it to last I'd throw warranty to the wind and install a better VB. If it's a lease or a fleet vehicle, that's different.

Rear wheel lockup doesn't sound like a good time, although allegedly they fixed this in '26 -- and it's also allegedly the only thing they fixed despite GM saying "it's all better now."
 
Yeah, enough of a problem Allison pulled licensing and forced dealers to walk out to existing vehicles and pull the badging (although I chuckle as I wonder how many actually complied)

If I had one and I wanted it to last I'd throw warranty to the wind and install a better VB. If it's a lease or a fleet vehicle, that's different.

Rear wheel lockup doesn't sound like a good time, although allegedly they fixed this in '26 -- and it's also allegedly the only thing they fixed despite GM saying "it's all better now."
Had a guy respond on another forum just now saying he runs tes 668 in his 10l1000 and it shifts like normal.
 
Had a guy respond on another forum just now saying he runs tes 668 in his 10l1000 and it shifts like normal.

If a "Quick Learn" was performed with the higher viscosity ATF....I have no doubt the unit would perform normally.

I do doubt a higher viscosity ATF would help any of the issues as I haven't seen any excessive geartrian, bearing, or bushing wear in the 10L1000.
 
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