Transmission Fluid Change August 04, 2025, 10:40:12 am I dropped the transmission pan a couple of years ago, put in a new filter and replaced the pan fluid. Yesterday, I drained the pan via the drain plug (thank you, fomoco) and replaced the fluid. For pushers and big trucks, Allison recommends this non-flush method (2 times) to achieve what they consider effectively a 100% change. So I'll go with that and consider it 100%. jor
Re: Transmission Fluid Change Reply #1 – August 04, 2025, 11:40:07 am If true and adequate, this would definitely simplify the flush process. Can you provide that Allison link?Steve
Re: Transmission Fluid Change Reply #2 – August 04, 2025, 01:11:57 pm QuoteCan you provide that Allison link?All I can find is references to a couple of Allison bulletin numbers. QuoteThe specific Allison service bulletin that details the two-step fluid change process to achieve 100% TranSynd fill is Allison Service Bulletin No. 1108. This bulletin describes that after draining and refilling with TranSynd, you must operate the vehicle, then drain and refill again to reach nearly 100% TranSynd, at which point you may follow extended change intervals.You may also see supporting information in service communications citing Service Information Letter 10-TR-99 Rev B and 13-TR-90 Rev E within Service Bulletin 1108.I used this method in a couple of pushers I've had with Allisons (3000 and 4000 models). It is intended for those with regular transmission fluid that wish to change to Allison's Transynd. If you do it twice the fluid is considered 100% Transynd and you are then covered for the very long fluid change interval. Anyhow, I'm comfortable with this in lieu of flushing.Doing this on our LDs is a pleasure. On the pushers it was 40 quarts and two filters. jor 1 Likes
Re: Transmission Fluid Change Reply #3 – August 04, 2025, 01:15:43 pm A full flush on the LD uses I believe about 27 qts. How much did a simple drain use each time?Steve
Re: Transmission Fluid Change Reply #4 – August 04, 2025, 04:41:34 pm QuoteHow much did a simple drain use each time?8 1/2 with the pan off and 7 1/2 with the drain plug. Long way from 27!!! Nevertheless... jor
Re: Transmission Fluid Change Reply #5 – August 05, 2025, 09:44:06 am I would say if 16 qts accomplishes, say 98% exchange, that would be more than adequate.Steve
Re: Transmission Fluid Change Reply #6 – August 05, 2025, 02:47:33 pm Quote from: Steve - August 05, 2025, 09:44:06 amI would say if 16 qts accomplishes, say 98% exchange, that would be more than adequate.From personal experience, it takes 22 quarts of transmission fluid to flush the 4 and 5-speed transmissions.8-1/2 quarts is 36% of the capacity. Changing the second time does not remove 7-1/2 quarts of old oil since a third of the drain oil is new and the rest is old oil. This works out to be about half the old oil is replaced with 16 quarts, not 98%I don't think most of us would be happy with partial engine oil or coolant changes.For an extra 6 quarts, the old oil is completely removed when flushing. Partial flushes throw away some of the new oil.If you are going to the trouble of jacking the rig up, draining and removing the oil pan to replace the filter, then refilling, draining, and filling again, for a little more work, you can replace all the oil rather than dilute the old oil. IMO, it's worth the extra time and a few more bucks.When our transmission was rebuilt and upgraded to diesel specifications, John Wood, the builder, agreed that total flushes, using the method I have described, were best, especially for rigs that tow.. Larry
Re: Transmission Fluid Change Reply #7 – August 06, 2025, 04:51:15 pm When my first 2010 LD reached 30K miles I mistakenly thought the trans oil needed replacing and took it to our local Ford truck dealership. I didn't realize Ford changed the first oil change to 60K miles because Ford was now using synthetic trans oil. They were also using synthetic rear end oil in the rear differential. They gave the job to a younger new employee who finished the job and I went on my way. While towing a Honda CRV across western Texas I was traveling over some high roller coaster hills when I saw black smoke coming from under the middle of the coach. Upon checking the trans oil was dripping over the exhaust pipe. Coach Net responded and towed us 70 miles to the Lubbock TX Ford dealership. The shop supervisor, Greg Moore, said he had the most experienced transmission tech in west Texas. He was right! Moore allowed us to stay overnight in the motorhome inside the shop until they could fix it. He gave us the key to his shop so we could walk about outside. He even took us out to a good restaurant for our meals. He wasn't kidding about the trans tech, he removed the transmission, took it all apart to find the issue. All the components were good and undamaged? There were no seal or gasket leaks. Just to be sure it was in good shape when finished he put in a new torque converter under warranty. We finally determined the Florida Ford tech had over filled the trans oil causing it when hot to flow out the breather cap on the top of the housing. The tech explained that when replacing the oil it is cold and expands greatly when heated. Therefore one should only fill to where the oil (with the engine running) only reaches the 'Need fill' mark or better yet just touching the bottom of the dip stick. He also told me when replacing the oil, filter and gasket totally flush the system of all the old oil. To do this after the pan is replaced and after oil is being added remove the return line from the trans oil radiator and drain that oil until you see the fresh oil appear. Immediately turn off the engine, reconnect the return line to the trans and add the oil as described above. Make sure the oil meets Fords specifications. 5 Likes
Topic: Transmission Fluid Change (Read 302 times)
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Topic: Transmission Fluid Change (Read 302 times)
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