Transmission Question Re 4l80-e

TallPaul · July 12, 2007

I have a 2000 Gulfstream Conquest Sport 28' Class C motorhome on the cutaway one ton Chevy van chassis with a 454 V8. I learned the build code for the tranny is MT1 and on a Google search tied that to the model 4L80-E transmission. Also found out that tranny holds approx 14 quarts ATF with about 7.7 qts draining on a pan drop. I assume there is no torque converter drain plug. Looking for any info on this trans, durability, etc.

Anyway, I have 15,000 miles on this rig and my plan is every 15K miles to drain the pan (by syphon out the dip tube) and refill with Redline D4 ATF. Book says 100,000 mile ATF changout schedule, but 50,000 mile for hard service. So I figure I should be on the 50K cycle, but the filter can go 100K. With the partial changeout every 15K miles I calculated that I will never have more than a miniscule (maybe 3%) amount of tranny fluid that is more than 50K miles old, and so I would never have to do a complete tranny flush. Also, I can do the filter and maybe will do at 50K just for peace of mind. The Redline will hold up better than most tranny fluid since it is ester based (only base oil that can take the heat of jet turbine engines) and has a GL-4 level of antiwear additive. Redline D4 meets Dexron III spec which is what I am supposed to use.

I notice there are shift kits for this tranny, but she seems to have nice firm shifts, so I will leave it alone--for now. Since it is all electronically controlled, conceivably one could put in a small console to manually shift all gears, like maybe pushbuttons or something. Why? Well, when I go into the Rocky Mountains, or even out east (can't spell that other mountain range) I need to use lower gears. It is always a tad risky to be pulling down into lower gears with the lever as you can overshoot, or does it not go down until it is safe, that is, if I pull it into first at 55 mph, will it only go to 2nd until a slower speed and then 1st. If so, good, but probably not a good practice. Mostly in Michigan I need to pop into 3rd at times. However, it seems to do that nicely automatically. My old motorhome (Ford 460 with E4OD tranny) didn't like to stay in 3rd so I would have to manually select it, but this Chevy is behaving nicely on that aspect.

Anyway, it's my new toy and I am very excited about it and want to keep it in great mechanical shape.

Thanks

ATMINF · July 12, 2007

I am not a trans guy but alot of stuff that you are planning to do sounds good. Just remember that the 4L80 is based off of the old Turbo 400 tranny and there are even parts that interchange with it. It is a very durable transmission and can last a very long time as long as it is maintained. I also believe that GM has put the new sythetic tranny fluid in the new 3/4 tons that have the 4L80 in them, so you can also check out the new dextron than is put into them and see how well that will fit into your application. Good luck.