6L80 external filter DIY

[Black02Silverado]

On 2/15/2026 at 10:36 PM, cossack said:

I did, here is a link to post I made on another forum (hopefully its allowed). I changed it in 2019 and in 2023. 

Link?

[cossack]

1 hour ago, Black02Silverado said:

Link?

Try it now, not sure why its made so complicated 

[Z45]

I looked up the spin-on atf (hydraulic) filter for the Allison trans and the burst strength is 780 psi and bypass setting of 8 psi.  Adding a external filter can be a risky endeavor. See below.

 

I know someone who rigged a spin-on bypass filter on a 2008 Sprinter L4 (2.1) Diesel van and coincidentally his  transmission failed. Used a Ford 6.1Ldiesel oil filter.  So he got a used trans and installed that, trans went again. Mind you he is driving a lot of miles as a LTL carrier (7,000+ miles monthly).  So after 2nd trans failed he did not hook up the bypass filter and he went some 200,000+ miles w/o another failure. Retired the van with almost 600,000 miles for a 2016 (he got at drug seizure auction).  He is confident adding that bypass filter was what caused the trans failures, starving fluid creating excess heat???  

Edited February 18 by Z45

[Grumpy Bear]

2 hours ago, Z45 said:

I looked up the spin-on atf (hydraulic) filter for the Allison trans and the burst strength is 780 psi and bypass setting of 8 psi.  Adding a external filter can be a risky endeavor. See below.

 

I know someone who rigged a spin-on bypass filter on a 2008 Sprinter L4 (2.1) Diesel van and coincidentally his  transmission failed. Used a Ford 6.1Ldiesel oil filter.  So he got a used trans and installed that, trans went again. Mind you he is driving a lot of miles as a LTL carrier (7,000+ miles monthly).  So after 2nd trans failed he did not hook up the bypass filter and he went some 200,000+ miles w/o another failure. Retired the van with almost 600,000 miles for a 2016 (he got at drug seizure auction).  He is confident adding that bypass filter was what caused the trans failures, starving fluid creating excess heat???  

 

I think he wore a blue suit twice and it rained twice then he wore jeans and it didn't rain at all.

 

The Allison pumps bypass setting is somewhere between 50 and 70 psig (application dependent) . Well beyond the 8 psig filter bypass setting. As the pump is a vane pump and indeed a positive displacement pump, the filter being in bypass would have zero impact on flow (starving) and minimal on fluid heating. No more so that the few psi it takes to circulate the oil itself, even through a cooler on a cold day. 

[cossack]

On 2/18/2026 at 9:06 AM, Z45 said:

I looked up the spin-on atf (hydraulic) filter for the Allison trans and the burst strength is 780 psi and bypass setting of 8 psi.  Adding a external filter can be a risky endeavor. See below.

 

I know someone who rigged a spin-on bypass filter on a 2008 Sprinter L4 (2.1) Diesel van and coincidentally his  transmission failed. Used a Ford 6.1Ldiesel oil filter.  So he got a used trans and installed that, trans went again. Mind you he is driving a lot of miles as a LTL carrier (7,000+ miles monthly).  So after 2nd trans failed he did not hook up the bypass filter and he went some 200,000+ miles w/o another failure. Retired the van with almost 600,000 miles for a 2016 (he got at drug seizure auction).  He is confident adding that bypass filter was what caused the trans failures, starving fluid creating excess heat???  

 

What do you think the filter does to cause transmission to give out?

 

I'll try and give updates every so often. If I still own the truck when transmission gives out, I'll post it here.

 

 

[Z45]

18 hours ago, cossack said:

 

What do you think the filter does to cause transmission to give out?

 

I'll try and give updates every so often. If I still own the truck when transmission gives out, I'll post it here.

 

 

Have no idea.   Blame it on "unintended consequences" or maybe the particular way he installed it was a problem.  

Edited February 21 by Z45