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Discussion Starter #1
2007 DMAX

So over the last 2 weeks I noticed a sound from inside the truck that progressively increased with speed. The truck seemed to shift and accelerate ok.
Then today, I'm at cruise 70mph for a few miles, then when I give it throttle, trans starts slipping. Next thing I know no forward motion.

Pull over. Truck rolls freely in any gear including park. Driveshafts in tact.

So, now its trans time most likely. Which trans would you put in? Same one? stock? Looking for suggestions.

Thanks.
 

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2007 DMAX



So over the last 2 weeks I noticed a sound from inside the truck that progressively increased with speed. The truck seemed to shift and accelerate ok.

Then today, I'm at cruise 70mph for a few miles, then when I give it throttle, trans starts slipping. Next thing I know no forward motion.



Pull over. Truck rolls freely in any gear including park. Driveshafts in tact.



So, now its trans time most likely. Which trans would you put in? Same one? stock? Looking for suggestions.



Thanks.


Depends if youre gonna be running stock power for the life of the truck


-head studs and gaskets
-66mm (stupid loud)
-5” straight pipe axle dumped
-shimmed
-full s&b intake and mouthpiece
-dans diesel 800 HP built trans with biller stator
-dans built trans tunes
-glowshift EGT, boost(not working because i broke it), fuel pressure(have not found a sender to work for it help please), edge cts2
-PPE sleeves
-fuel lab 100 gph lift pump
 

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Discussion Starter #3
Truck is 100% stock with a PPEI DSP5 tune. I usually run position 3. I might do some fuel system mods to build up more power that way.

I'm all ears...I hate to put a stock trans back in and smoke it. This one shuttered for a long time so something a little stronger than stock I guess.

Thanks.
 

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Truck is 100% stock with a PPEI DSP5 tune. I usually run position 3. I might do some fuel system mods to build up more power that way.



I'm all ears...I hate to put a stock trans back in and smoke it. This one shuttered for a long time so something a little stronger than stock I guess.



Thanks.


Sounds like you might wanna look into a mildly built trans like 600 HP, they usually come with upgraded converter, clutches, and valve body as well as a few other little supporting things. Theyre not pricey like the 800 HP builds but its harder to find a shop that offers this kind of build. Duramax tuner is one i know of that comes to mind. If youre looking to run more power than you make on stock fuel, stock trans do not usually hold up in the long run. If you can keep your foot out of the pedal on the shifts like 4-5 or 5-4 or 6th and you stay out of position 5 you could make a stock one last. Its all in how you treat it, allison will love you forever until youre mean to her. Then she starts to get sick of your shit


-head studs and gaskets
-66mm (stupid loud)
-5” straight pipe axle dumped
-shimmed
-full s&b intake and mouthpiece
-dans diesel 800 HP built trans with biller stator
-dans built trans tunes
-glowshift EGT, boost(not working because i broke it), fuel pressure(have not found a sender to work for it help please), edge cts2
-PPE sleeves
-fuel lab 100 gph lift pump
 

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IT IS PROBABLY NOT THE TRANSMISSION. The parking pawl works on a ring attached to the output shaft of the transmission. There are no clutches or gears between it and the rear of the trans. If park won't hold it is very unlikely that the transmission is at fault. Pull the dipstick and look at the oil. If it is still red and doesn't stink like it has been burnt then it is unlikely that the transmission is at fault.

The likely culprit is the transfer case. Try putting it into 4x4 or low range and see if it will front wheel drive. If it will then the transfer case is the problem for sure. Even if it won't FWD it is probably still the transfer case. If it won't shift then it is confirmed that it is the transfer case.

Remove the drive shaft from the differential and turn it by hand. See if you can feel any ratcheting type action like it is trying to catch but just can't hold. That would be splines inside the transfer case.

Pull the drive shaft out of the transfer case and look at the spline on the slip yoke. If you are living right all you have is a stripped spline that a new U-joint yoke would fix.

With the drive shaft out try turning the transfer case tail shaft. See if you can feel ratcheting. Remove the drain plug and see if there is a lot of debris there.

Take off the transfer case (it isn't simple but it isn't too tough either) and see if the splines are still on the output of the transmission shaft and the input shaft of the transfer case. If the splines are stripped off the transmission output shaft then the transmission will have to come out and be completely disassembled because that shaft is the first thing you put into the case when assembling it. If you get that far it would be a good idea to put in some new clutches with upgraded linings but you don't necessarily need a complete overhaul.

I really think you will find that the t-case is FUBAR. If it is I would recommend just getting a low mileage junk yard replacement. Rebuilding a t-case isn't all that hard but good replacements are not too expensive. I found an electric shift t-case with 59,000 miles for $875. If you have a floor shift then I found one with 40,000 miles for $1,000. That isn't free but it is a whole lot cheaper than a rebuilt trans.

If you haven't been abusing your Allison with big tunes and other mods then it is very reliable. You would have a hard time breaking it with a stock setup or even mild tunes.
 

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Discussion Starter #7
it was the TRANSFER CASE. Apparently they said something rubbed a hole in it and all the lubricant disappeared destroying it. Now I have to figure out how to check the level . I still haven't seen the part yet.
 

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What you may have had is the well known pump rub problem. Inside the transfer case is a small pump that lubricates the gears and some bearings. That pump sits loosely inside the case but it is attached to the main shaft. The lugs that keep the pump from rotating with the shaft are steel and engage slots in the case.
Since nothing in life is perfect, there is a bit of wobble in the shaft, which translates to the locating lugs on the outside of the pump rubbing against the case.

Over time the case wears through. The oil leaks out of the t-case and without lube it dies a horrible death. If you park on asphalt or concrete you would likely see the oil spot but if you park over gravel or dirt then it is easy not to notice.

The shudder you speak of may have been the splines and gears inside the t-case slipping and binding as it died. I would replace the t-case first and see what happens. It isn't necessary to do anything to the transmission to replace the t-case so it won't save you much to do the converter now rather than wait.

If you have already done the t-case and it is still shuddering then a fluid change with the right stuff might be all you need. Does your old fluid look and smell good?

There are lots of threads on ATF in this forum but the most authoritative is this one.

https://www.duramaxforum.com/forum/transmission-shop/95342-former-allison-transmission-fluids-engineer-mr-transynd.html
 

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Note: The trans speed sensor is located at the rear of the transfer case- and when the fluid leaks and damages the TC, - that can affect to trans shift-!

As the Wizard noted - you have something broken in the TC-
 

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Discussion Starter #11
a pic of the final cause: shop is saying all the fluid came out of that hole on TOP of the xfer case. They showed me how the
star looking washer slapped around in there to cause it. I got to tell jiffy lube about this. they could probably save a few chevy's from xfer case death.

 
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