I bought a high mile suburban and the as far as I know it's the original trans, and I have no idea when the fluid was changed last. It is pretty dark but not burned. The truck shifts perfect and shows no signs of a problem. I have heard don't touch it, because new fluid may shock it into problems. I want to introduce a bit of Lucus, but fear this may clean out and dislodge sludge. What you all think?? Change it? Or. Leave it alone? Oh and yes I tow a trailer with this truck.

General advice I've heard is to drain it and refill with new fluid, as opposed to a flush. Depending on the vehicle, you will get about 1/3 of the fluid or more. Do this a few times in a short time span and you will have mostly new fluid. This doesn't disturb wear particles like a flush will.

Hope you got it cheap. I’d be shocked if it hasn’t been rebuilt. I’ve had several Burbs and Silverados and rarely got 150k out of a tran. I’d change it and be ready to rebuild it. My sons 2002 Chevy 1500 just failed last week. 180k.

Drain the fluid and change the filter. Do not flush and do not add any additives.Good luck...

My uncle's 2003 explorer has 350K on the original transmission, and he has them drain, swap filter, and refill. No special additives. Best of luck.

I agree with avoiding a pressure flush.You should drain and re-fill. Sometimes this can dislodge sludge or debris, causing near-immediate failure. If this happens, keep in mind it only accelerated the inevitable. Better find out before a long trip.FWIW - I've gone to 100,000 drain and fills on my transmission. I'm a little over 450,000 and I'm a little over my 100,000 interval now. I just run the Napa stuff meeting factory spec.

Trans fluid change on my 2007 suburban with 320,000 miles.

coolmom42
Explorer II
Apr 03, 2018
General advice I've heard is to drain it and refill with new fluid, as opposed to a flush. Depending on the vehicle, you will get about 1/3 of the fluid or more. Do this a few times in a short time span and you will have mostly new fluid. This doesn't disturb wear particles like a flush will.
Big_Katuna
Explorer II
Apr 03, 2018
Hope you got it cheap. I’d be shocked if it hasn’t been rebuilt. I’ve had several Burbs and Silverados and rarely got 150k out of a tran.

I’d change it and be ready to rebuild it.

My sons 2002 Chevy 1500 just failed last week. 180k.
FishOnOne
Nomad
Apr 03, 2018
Drain the fluid and change the filter. Do not flush and do not add any additives.

Good luck...
Fordlover
Explorer
Apr 03, 2018
My uncle's 2003 explorer has 350K on the original transmission, and he has them drain, swap filter, and refill. No special additives. Best of luck.
carringb
Explorer
Apr 03, 2018
I agree with avoiding a pressure flush.

You should drain and re-fill. Sometimes this can dislodge sludge or debris, causing near-immediate failure. If this happens, keep in mind it only accelerated the inevitable. Better find out before a long trip.

FWIW - I've gone to 100,000 drain and fills on my transmission. I'm a little over 450,000 and I'm a little over my 100,000 interval now. I just run the Napa stuff meeting factory spec.
Turtle_n_Peeps
Explorer
Apr 03, 2018
What year is it? What tranny? A glide? A 350? 700R4? 4L80E? In any event you are going to have to drain it if you want a reliable unit. Better to find out now than on the road.
rjstractor
Nomad
Apr 03, 2018
Turtle n Peeps wrote:
What year is it? What tranny? A glide? A 350? 700R4? 4L80E? In any event you are going to have to drain it if you want a reliable unit. Better to find out now than on the road.

A 2007 is going to be a 6-speed. But I'm suspect of the whole post because according to RV.net Tow Vehicles lore, there is no possible way for a gas-powered tow vehicle to approach anywhere near 320,000 miles. Diesel is the only way to get over 250K!! ;)
Bionic_Man
Explorer
Apr 03, 2018
rjstractor wrote:
Turtle n Peeps wrote:
What year is it? What tranny? A glide? A 350? 700R4? 4L80E? In any event you are going to have to drain it if you want a reliable unit. Better to find out now than on the road.

A 2007 is going to be a 6-speed. But I'm suspect of the whole post because according to RV.net Tow Vehicles lore, there is no possible way for a gas-powered tow vehicle to approach anywhere near 320,000 miles. Diesel is the only way to get over 250K!! ;)

I am pretty sure that it would still be the 4L60E. I don't think they went to the 6 speed until 2010 as standard equipment. 2009 it was an option.

Either way, I would go with the suggested drain and fill, not flush.
LIKE2BUILD
Explorer
Apr 03, 2018
Be aware the drain plugs on those pans are notorious for corroding in place. I tried everything under the sun to remove the drain plug on my ‘03 Yukon XL and all I did was strip the bolt head. It seems that’s a very common thing. If your burb is an old body style you’ll have to take the exhaust loose to be the pan off to change the filter.

KJ
MARK_VANDERBENT
Explorer
Apr 03, 2018
Thanks for all the good advice.My truck does have the heavy duty towing package and trans temps are very stable and consistant.