Allison 5sp: 3rd and 4th gear slip

[TrueStreetVW]

So yesterday I had about 5 to 6000 pounds of firewood on my truck and trailer and I noticed that it felt like the trans was slipping in 3rd and 4th gear at like 2100 to 2600rpm. I had my diablo predator set to the towing tune at the time and was driving the truck easy.

Any ideas as to what could be causing my issues? Truck had about 162,000 miles on it. Any help would be greatly appreciated.

 

[TrueStreetVW]

No one has any ideas?

 

[GeneralTJI]

Explain what you mean by slipping... During the shifts or while in gear? TC locked up or not? (tow haul)... Any codes thrown? Fluid temp ok?

 

[TrueStreetVW]

Explain what you mean by slipping... During the shifts or while in gear? TC locked up or not? (tow haul)... Any codes thrown? Fluid temp ok?

Not slipping during shifts. It would slip in the middle of the gear from
2100 to 2600rpm then it would grab again. Tow haul mode was on and the fluid temp never went over 125*F

 

[GeneralTJI]

What year truck is that? any other mods besides the predator?

 

[TrueStreetVW]

It's a 2004. Just the predator and muffler delete. I have had the tuner truck loaded with the 120 hp tune and had no issues until I lowered it to the 40 hp tow tune to haul the firewood.

 

[jc1843]

Did it throw a CEL, and do you have any codes-?? Usuall a slip will cause a fault light.

 

[MACKIN]

Could just be a relearn issue as the TCM was use to the higher tune and now you cut the power back and it needs to relearn. If it slipped it would have thrown a code and the SES light would have illuminated.

 

[TrueStreetVW]

I had no trans codes only a glow plug code. But is sure as hell felt like slip.

How long does it take to relearn? I had already driven about 90 to
100 miles since I switched the tune so I could tow.

 

[GeneralTJI]

How long since you replaced the spin on allison filter btw? Wouldn't hold my breathe, but it might be good to change that regardless (try to change them pretty often, say every 10k miles) And always use the actual Allison brand filter...

 

[TrueStreetVW]

It's been on for at least 25000 miles. I will try the spin on. Any idea where is a good place to get one from?

 

[GeneralTJI]

Online or an Allison dealer (not gm)

Merchant Automotive gets things out pretty fast, but you pay a lot for shipping (unless you buy several to make it worth it). There are some other's online that are similar.

The part number is 29539579 if you searching around...

There are probably some supporting vendors here on the site that have good deals on them? If I knew who I would steer you that way first!! Maybe somebody can chime in....

 

[TrueStreetVW]

Thanks for the help. Hopefully it will solve my issue.