[Dale]

Dale,

If Dextron is what you have been using all the years you’ve owned the bus, why not stick with it? I don’t know what you can expect in lower temps if switching to Transynd or other synthetic, maybe 10 degrees. Im repeating myself here again, but at seminar we had at United Engine in OKC a few years back, I asked about switching to Transynd for my 8V 5 speed and they advised against it and said to stick with Dextron. I figure they knew what they were talking about.

[Archived]

I just bought a gallon of Transynd and it was $430 at our local Freightliner store. In bulk it is slightly less, but that is today’s price on prepackaged jugs.

Glad it doesn’t have to be changed too often!

[Larry & Diane]

If we look at the Allison fluid change recommendations for the 6 speed transmission they use a time interval and miles, whichever comes first. The time interval for Transynd is 4 years, and the mileage interval varies based on what Allison considers heavy duty or harsh service. With a retarder the interval in miles is 1/2 the miles for a transmission not equipped with a retarder. I asked Allison why and the reason stated was the higher temps created by the retarder.

Having already been aware that temperatures on oils at the high end are going to shorten the life I have established a conservative temperature limit. I still observe the time limit, bus I am sure my transmission fluid still retains all its properties. I use 230 mainly because that is a temperature mark on the transmission temperature gauge.

In reality the computers will limit transmission temps by disabling the retarder once temps reach 300, but I wanted to be conservative. I agree with Joel in that we probably are capable of substantial time limits is we are not seeing or smelling cooked fluids.

[Doug]

In severe service (high speed cruise was worst, 57,500# GVW) on my old 8V-5speed, I observed 30 degree temp reductions changing from moderately used dexron to trans-synd. Bear in mind, increased trans temps transfer to the engine cooling system through the coolant/trans cooler and increase engine temps.

Many of you will never see this type of use or enough miles to make a difference, but IMO, I would rather use the best approved product and be safer than to save a couple bucks on a maintenance issue which is not performed frequently by most. Additionally, in this case, the synthetic fluid extends the drain interval which will negate some of the cost detriment factor and less maintenance ist good.