Did the switch from the 15w40 engine oil in the transmission on my 1997 M1078 LMTV with WTEC II to ATF.
Followed "8-9 Transmission Oil Filter Replacement" procedure found in TM 9-2320-365-20-3 page 8-32. However, I deviated from the procedure and did NOT remove the front driveshaft (WARNING, proceed at your own risk).
I do not recommend or suggest anyone perform any maintenance or repairs outside of what is in the TMs I am only indicating what I choose to do. After completing the change over I followed the WTEC II calibration procedure to put the transmission into learning mode to relearn the shift patterns. This write-up is NOT a substitute for following the TM!
The TM procedure only has you drain/fill once with a filter change but that is when you are doing so with one type of fluid (standard filter and fluid change). So I further modified the procedure to make sure I got all the 15W40 out of there with 3 drain/fill cycles and did not switch out the filters until the last drain/fill.
Why I did it
I wanted better shifting, cold weather behavior, and longer transmission life. My LMTV also had a nasty jerking effect when downshifting from 3-2 when coming to a stop (which is still present after the switch to ATF). I did a LOT of reading on the pros and cons of keeping the 15w40 in there or switching to ATF and also did some reading in the 5 Ton forums even though they have a different trans setup. I referred to the Allison website for recommended oils and several others have noted that the engine oil is down on the list of recommended fluids for both performance and life of the transmission. The top tier fluid is the full synthetic TRANSEND TES-295 (but I didn't want to spend upwards of $700 in fluid to do the swap initially so based on the Allison fluid table I went with Mobile ATF D/M which does adhere to the TES 389 (Mobile Multipurpose ATF) standard and is approved by Allison. It is basically Dextron III NON-Synthetic fluid and is much cheaper than TRANSEND. There are tons of discussions on what happened to D3 and the whole GM/Allison story that I won't go into in this thread. In my research and opinion, DO NOT use Dextron IV Synthetics (issue with seals in LMTV trans) only TRANSEND approved. Hopefully this thread doesn't turn into a war on why. The plan is to run with the D/M ATF for a year then switch to the TRANSEND full synthetic.
Modification without removing front driveshaft
I was able to remove and reinstall the driver side filter without removing the driveshaft. you can get to all the bolts with either ratchet and extensions or wrenches with the driveshaft in place. The issue is that 2 to 3 of the bolts, depending on the position of the yoke, do not allow you to get a torque wrench on them for final torque. I torqued those bolts by feel alone so this is where the "do it at your own risk" comes into play. The only other side effect from this is that when you pull the filter it is attached to the cover so you have to pull them apart on removal to clear the driveshaft and push them together with the filter partially installed into the filter well on the transmission for installation (see pic). you will get fluid all over the driveshaft.
View attachment 603236
View attachment 603237 this is how the filter and cover are removed and installed (new filter in pic). This pic is of the install where I had to first insert the filter alone into the transmission housing then push the filter and cover together in this position for installation. You have to have them mated together before you push the assembly into the transmission. For removal you slide the unit down as shown then pull the filter off the cover. Hopefully this makes sense as this is the most complex part of the whole operation (and not really that difficult). - In this pic the filter/cover assembly can be pushed together up into the transmission but there is no further downward side movement to allow them to be removed together.
View attachment 603243this shows the bolts that I was unable to get a ratchet on or torque wrench for final torque. I used an wrench to torque by feel (which I know is not accurate but that's what I did and no leaks so far). There is enough room to remove and install all 6 bolts with the driveshaft in place.
Stuff
1. Supplies - 3 each, 5 gallon buckets with lids to store the massive amount of transmission fluid I will be dealing with and an additional 2 gallon bucket to catch the fluid from the filters.
2. Allison transmission holds around 10 gallons of fluid total with a TM referred 7 gallons at filter change. I did not get that much out during each drain.
3. 15mm wrench and sockets for the filter cover bolts.
4. torque wrench
5. 21 gallons of Mobile ATF D/M (non-synthetic). I used less than what I purchased (16.75 gallons total).
6. Transmission filter kit (got off *Bay) - NOTE: kit only came with 1 o-ring for drain plug with the LMTV having two drain plugs with O-rings, transmission and transfer case. All other O-rings, filters, and gaskets were included in the kit.
Drain and Fill Information
- Total of 3 drain/fill cycles with filter change after the 3rd drain but before I filled the trans.
- The drain plug for the transmission is VERY close to the exhaust pipe so be careful for burns and there is limited room to get a 3/8 ratchet into the plug.
- Transmission fluid will get all over the exhaust pipe and splatter into the 5 gallon bucket for about 10 seconds before it settles down to a steady stream.
- At Drain/Fill #3 when pulling the filters there was no sign of 15W40 oil in the filters and only clean beautiful ATF drained out of the filter housings.
View attachment 603258 you can see how close the exhaust is to the transmission drain plug
I was able to accurately measure each drain/fill and total AFT used because I used 1 quart bottles of ATF. Not my choice it is just the way I had to buy it. Cheaper to get 5 gallon buckets of ATF.
It appears that the transmission and transfer case drain about the same amount of fluid. Less out of the trans on drain #1 with the 15W40 but assuming that is due to the thicker oil taking a lot longer to drain out thru all the fun stuff in the trans than the transfer case.
View attachment 603234 the bucket on the right is from the trans and the other is the transfer case. In this pic it looks like the transmission drains a lot less fluid but if you let the engine oil drain longer they just about equal out. in fill #2 and #3 they were just about the same amounts in each bucket. You can see all the splatter to the right of the transmission bucket on the ground from the fluid initially pouring out onto the exhaust for the first 10 seconds or so of the trans drain.
Drain/Fill #1 - Initial
-Warmed up truck to operating temp and drove around for 15 minutes.
-Placed two 5 gallon buckets under the transmission drain and the transfer case.
-Total fluid drained 5 gallons (let both trans/tcase drain until there was no steady stream of fluid).
- filled transmission at the fill tube with 5 gallons of ATF
-So, we have half ATF and half engine oil.
-Didn't want to drive around for 30 minutes like that so I started the truck, warmed it up for 5 minutes, shifted thru N,D,R,N for 30 seconds each then drove around for 5 minutes at very slow speed to not put too much of a load on it.
I had previously read in the 5 ton forums (again, totally different trans setup than LMTVs) about bad things happening at this point of the fluid change over so I went the cautious route to not put the trans under too much of a load for very long. There is a LONG post in the 5T forum about a few people burning up a gear after this swap but there were many that were successful and it wasn't clear if the guys that had problems were already dealing with imminent failures in the trans. Let me be clear, I just leaned towards caution when in the middle of the switchover with 50/50 engine oil and ATF, which may have been unwarranted, but that is what influenced my decisions.
Drain/Fill #2
-Combined the 5 gallons from Fill#1 into the 3rd bucket so I had two empty buckets for round 2.
-Drain total of 5.5 gallons on this round.
-Filled transmission from fill tube with 5.5 gallons of ATF.
-Performed calibration procedure to put transmission into learn mode.
-Started truck and waited for warm-up to operating temp then shifted thru N,D,R,N for 30 seconds each then did a long 40 minute drive. Transmission shifted thru all gears and was noticeably smoother on upshifts but still had lurch from 3-2 downshift when coming to a stop.
View attachment 603235
Drain/Fill #3 (Final with filter change)
- plenty of room left in the two 5 gallon drain buckets so did not empty them.
- Again, 5.5 gallons drained from the transmission and transfer case combined.
- changed out filters - approximately 1-2 quarts of fluid held in the filters and housings. let everything drain to include the filter housings overnight.
- refilled transmission using a total of 6.25 gallons of AFT.
- warmed up the truck an drove around. Shifts great but the 3-2 downshift lurch when coming to a stop is still present). No leaks!
View attachment 603238 this is the passenger side filter housing. All bolts are easy to get to and expect a quart of fluid do drain out when you pull the cover.
View attachment 603239Filter and filter cover are removed and installed as one assembly (Old filter in pic). There is a hole and o-ring on the bottom of the filter that holds it onto the cover.
View attachment 603240Filter and cover separated (old filter, O-rings, and gasket in pic). I followed the procedure in the TM and the filter kit to replace the number and size of O-rings that were on my original filters.
Total fluid used
16.75 gallons as measured using 1 quart bottles of AFT and filling transmission just under the full hot mark on the dipstick with a warm transmission (operating temp).
There was some shifting drained fluids between buckets prior to the final drain as well as dumping the fluid from the filter change into a 1 gallon container and a couple of quarts into my normal oil drain pan so in the end I have 3 completely full 5 gallon buckets, one single gallon container, and a few quarts in my regular oil drain pan which accounts for all the fluid fun.
Aftermath
Successful change over. The transmission shifts much smoother throughout all gears and doesn't have the lurch forward going up through the shifts. It also doesn't wind up the engine as much prior to upshifts. The only disappointment was that the LMTV still has the 3-2 downshift lurch/jerk when coming to a stop. When the weather warms up in a few months I will try the calibration procedure again to see if that does anything. There is no indication that the trans is in a learn mode (that I could tell) so I am not sure if it actually went into learn mode. If I could summarize the "feel" of the change I would say the truck seems quicker or more nimble but that is just OD's gut talking and my gut is big so I will just leave it at that. I am happy with the results.
Found the test port on the outside of the driver side filter housing on the transmission that I am planning on installing a trans temp sensor. It is a 1/4" hole/plug but not deep enough for a temp probe to just screw into the port and of course the temp sensor I have is 1/8". Working on finding an adapter setup which of course seems to be some kind of voodoo dealing with pipe threads vs. NPT threads... More to come on this.
View attachment 603252
I hope this write up is helpful and not too controversial. I put up a lot of information so I will go back and update this post if I catch an error. Another thank you to Lmtv772 for letting me text him throughout the changeover with words of encouragement and sending him the pics of the progress (it always helps to have a MV friend near by when doing this kind of thing even if its via text.
Thanks,
OD
Dino 
oil breaks down in time, change that oil and filter!