New to dramas

[Fifth wheeler]

Hi all. New to the Duramax club. I bought a 2016 high country with 277k miles T &D. I love the truck but about 1300 miles in and the Allison is giving me fits, grinding and seems to “disengage” in downshift?
I drained and replaced fluid and filters. I went with Dextron VI fluid. I replaced the internal wire harness because it was leaking through the connector and added EPC blocker while I was in there, same issues. What next?


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[Bdsankey]

Does it have any codes? Did you do a TCM tune as well or just ECM? Any material in the pan?

 

[2004LB7]

Moved to Mike L's trans talk. Might get better help here

 

[Fifth wheeler]

Does it have any codes? Did you do a TCM tune as well or just ECM? Any material in the pan?

P0700 and p0776 initially. Now no codes.. I didn’t do any of the tuning so not sure it seems like maybe just a tow tune? Unfortunately, I don’t have any history on the truck or the previous owners.


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[Fifth wheeler]

P0700 and p0776 initially. Now no codes.. I didn’t do any of the tuning so not sure it seems like maybe just a tow tune? Unfortunately, I don’t have any history on the truck or the previous owners.


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I opened the internal filter and nothing out of norm in there (a few small specs) I didn’t check spin on. No burnt smell and fluid was not new. Some of the solenoids had 2022 date codes so someone had been in there but maybe not recent?

After changing the internal harness ( leaking fluid through connection)
and one shift solenoid same thing?


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[Chevy1925]

Time to pull the trans apart

 

[Fifth wheeler]

Time to pull the trans apart

For sure…. Ugh.

I’m new to these trans but It seems like it works ok for a little bit, I can’t rap my head around it being a mechanical problem, seems like an electrical issue? Maybe cause I’m a mechanical engineer?


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[Ron Nielson]

Maybe some help here

 

[Chevy1925]

If you know what you are looking for with a scanner, you can maybe be lucky and it be a speed sensor but doubtful.

Your only other option is the tcase is shot internally causing the oss to read incorrectly. Could also be the source of your grinding

 

[Fifth wheeler]

If you know what you are looking for with a scanner, you can maybe be lucky and it be a speed sensor but doubtful.

Your only other option is the tcase is shot internally causing the oss to read incorrectly. Could also be the source of your grinding

Thanks. Never thought of the case?? The 4 WD worked fine but almost never used I would guess. It free wheels when it grinds so something slipping or electrically not shifting right?? I only have a rude mental scanner.


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[Chevy1925]

The bw tcase is known to have some internal issues on high mileage trucks. Mode shift collars can rub the dog teeth and cause a grinding.

Your going to need to isolate this noise and do some investigating via scan tool (watching sensors fo dropping out or weird numbers) and go from there

It’s highly likely its either part due to the fact you have no known past history. Probably ought to check your tcase fluid