M35A3- Changed transmission fluid now won't move?

[1SLEDHEAD]

Good evening! I'm not at all knowledgeable when it comes to transmissions. I changed the internal and external filters in the Allison transmission and drained and refilled with Castrol TranSynd. I measured 3.5 gallons of fluid that I drained out after dropping the pan and external filter and letting it sit overnight draining, which is more fluid than I expected to see. I added 3.5 gallons after reinstalling the pan. I let it idle up to operating temp and measured the fluid. Reads very high. I thought it might have to fill the cooler and external filter, so thought the level would be ok. Went to drive it this evening and it really didn't engage with any drive power. Finally it went about 10 ft, then it lost drive power. The transmission worked fine before I changed the fluid. Anyone experience this before? Hope I just overfilled it and draining some will resolve the issue? Appreciate your thoughts. Thanks!

 

[Jbulach]

@tobyS probably does, and I believe he has a transmission for sale as well. Any Idea what fluid was in it before you changed it?

 

[1SLEDHEAD]

Thanks for the reply! Fingers crossed it won't need a transmission as it hasn't been run long. It was a red fluid that came out, I assume ATF was in it already, but have also heard they sometimes would dye oil red to help locate leaks? I assumed it was ATF that I drained at the time...
It hasn't made any scary noises or shutter, just seems like it's in neutral. I didn't pre- fill the external filter, maybe air locked? I don't know enough about them. Thanks

 

[tobyS]

What did you find when you dropped the pan and filter? Was there a gritty feeling to the fluid or little aluminum balls in the old fluid? The clutches in these tranny's, particular 4th/reverse have old seals that leak and won't hold pressure on the clutch, then the slippage causes heat and can melt the aluminum piston holding pressure on the clutch pack.

 

[1SLEDHEAD]

I regret not inspecting the old fluid more closely. The transmission seemed fine before I drained it so I didn't give the fluid the attention I should have. The pan had limited grayish/black residue/ sludge on the bottom after I removed it, but really no metal flakes on either the pan magnet or the drain plug magnet to speak of. I'm thinking I'll remove some fluid tomorrow and give it another go. I didn't expect this outcome from a fluid change lol. I'm still cautiously optimistic.

 

[BEASTMASTER]

if if ain't broke don't fix it

 

[1SLEDHEAD]

So much truth to that!
I'm thinking I might have knocked the filter off the pickup tube or something... I'll dig into this further.

 

[glcaines]

So much truth to that!
I'm thinking I might have knocked the filter off the pickup tube or something... I'll dig into this further.

I suspect you are correct about the pickup. Nothing you did changing the fluid should have caused this. I would drain and pull the pan and hopefully find the pickup was the problem. Did you drain the torque converter? If not, you are mixing the expensive TranSynd with whatever unknown fluid was in there previously. If you look at LO 9-2320-386-12, the fluid capacity is a lot higher than the 3.5 gal / 14 quarts you drained. According to the LO, the capacities are as follows.
Dry Transmission: 21 quarts
W/Filter: 19 quarts
W/O Filter: 18 quarts
Since you only drained out 14 quarts, either the fluid level was very low or you still have a lot of motor oil or ATF in the transmission. I don't know the compatibility of Castrol TranSynd with either motor oil or the ATF and if it was ATF, what type of ATF. As a side-note, only Dexron 3 ATF should be used in the 1545 transmission or the TranSynd. Other Dexron ATF will damage the seals in the 1545 transmission. I suspect you have contaminated your new TranSynd, which is very expensive. Can you talk to the previous owner and find out what was in the transmission?

 

[sue]

Good evening! I'm not at all knowledgeable when it comes to transmissions. I changed the internal and external filters in the Allison transmission and drained and refilled with Castrol TranSynd. I measured 3.5 gallons of fluid that I drained out after dropping the pan and external filter and letting it sit overnight draining, which is more fluid than I expected to see. I added 3.5 gallons after reinstalling the pan. I let it idle up to operating temp and measured the fluid. Reads very high. I thought it might have to fill the cooler and external filter, so thought the level would be ok. Went to drive it this evening and it really didn't engage with any drive power. Finally it went about 10 ft, then it lost drive power. The transmission worked fine before I changed the fluid. Anyone experience this before? Hope I just overfilled it and draining some will resolve the issue? Appreciate your thoughts. Thanks!

Idle with the trans in drive and try going through the gears.
Did the filters in ours and filled a little over and had no problems
and and after a short drive fluid level was good.

 

[1SLEDHEAD]

Thanks for all the feedback on my issue! I messaged that past owner this morning, and found he drained and filled the transmission with Napa https://www.napaonline.com/en/p/NHF85405 Hydraulic Fluid, which has been discussed on here as being an acceptable fluid to use. Now I'm thinking the Synthetic Castrol TranSynd 668 may not be compatible? He didn't drop the pan and didn't change the filter, just a drain and fill. YES! This is getting expensive with all the TranSynd I've contaminated. With folks questioning the durability of these transmissions, I was trying to do the best thing for it by putting in the optimal fluid. I don't think I've damaged anything, but I need to find the right concoction to make it work again. A full flush might be inevitable Or a tow to my local truck repair shop to let the "experts" sort out my mess LOL.

 

[glcaines]

TranSynd is a very good transmission fluid, but only has one advantage over Dexron 3, according to Allison. You can go further between fluid changes with TranSynd than with Dexron 3. Dexron 3 is the recommended fluid for the 1545 transmission with TranSynd also acceptable. Motor oil works also, but the transmission doesn't shift as smoothly. The Army only went with motor oil to minimize the number of fluids it needed to support. Dexron 3 works great and is 100% compatible with the seals. NAPA brand is the same as Valvoline brand and a lot less expensive. I've found repeated drain, fill and drain again the best way to switch to Dexron 3. If I remember correctly, I did the drain and fill routine 5 times. I also drive several miles between the drain/fill, shifting up and down, including reverse, each time. This ends up changing out the fluid in the entire system. I bought NAPA Dexron 3 equivalent by the 5-gallon pail. I now have over 13,000 miles on my 1545 transmission since switching to Dexron 3 and zero problems. I routinely pull my XM1061E1 trailer heavily loaded with the A3 through the mountains and no transmission problems.

 

[1SLEDHEAD]

Thanks for the info, Gary! I'm in the process of messing with it again today. I pulled the external filter up near the front bumper and it was less an 1/4 full of fluid, giving me the idea that the transmission isn't pumping, so going back to the thought that the filter installation might be the culprit. The pan is difficult to get on and off, so in struggling to get it on, I might have knocked the filter. The hard copper air line, the driveshaft, the linkage brackets on the driver's side, it's a fight to get the pan on and off. Any tricks on an easier way to get the pan in and out?

 

[glcaines]

Thanks for the info, Gary! I'm in the process of messing with it again today. I pulled the external filter up near the front bumper and it was less an 1/4 full of fluid, giving me the idea that the transmission isn't pumping, so going back to the thought that the filter installation might be the culprit. The pan is difficult to get on and off, so in struggling to get it on, I might have knocked the filter. The hard copper air line, the driveshaft, the linkage brackets on the driver's side, it's a fight to get the pan on and off. Any tricks on an easier way to get the pan in and out?

Sorry, it's been several years since I removed the pan and my memory isn't what it used to be. I don't remember any particular problem with the removal, but if you are having problems, I probably did as well. I doubt if there is any permanent damage to your transmission since you haven't driven the truck so no slipping clutches, etc. Good luck.

 

[1SLEDHEAD]

Thanks for the reply! so I completely disconnected the linkage on the driver's side this time, including the bracketry for the sensor connectors, and "flipped" the linkage and that helped a lot! I also believe I found the culprit- a torn O-Ring at the top of the pickup tube!!! I must have rocked it and tore the o-ring somehow so the pickup tube wasn't sealing properly. Stand by as I'm getting it back together now. My lack of confidence with this transmission work got the best of me so I think I overthought the process, as I tend to do! LOL Thanks for all your support!

 

[1SLEDHEAD]

WOW! So the torn O-Ring did it! I must have had the up-pipe cocked just slightly so it didn't seal enough to draw the fluid up. I'm relieved and my truck is happy again. Thanks for all your input! I've always been hesitant to go too far with transmission work as I'm not familiar with them. I have everything back together and took it for a ride and it feels great! Crazy a 10 cent O-ring can take down the mighty M35. Huge waste of expensive TranSynd fluid, but could have been much worst. Learning curve for me! Appreciate this resource. Cheers!

 

[glcaines]

Congratulations on tracking down the problem and fixing it! Every time you work on something you learn something new.