Transmission servicing

gmc
sonoma

#1

My 2001 GMC Sonoma has 160,000 miles on it. I’ve maintained it, changing oil regularly, flushed the cooling system, replaced the water pump, etc. I last changed the tranny fluid at 85,000.



Given the truck’s age and mileage, should I replace the tranny fluid and filter?


#2

Of course you should, and so should you every 30,000 miles. Many perfectly good older cars bite the dust because the transmission fails, a most negected item.

The manufacturers are at fault here by trying to outdo each other pushing “low mainteance”.

If you read the “severe service” part of the maintenance, you will find a need to change fluid and filter every 15,000 miles or so. Double that and you will have the transmisssion last the life of the car. GM does not normally require this activity, and many GM cars do not even have a distick and filler neck.

I have never scrapped a car because of transmission failure, and the last time I spent any money on repairs was in 1976 on a Ford C-4 unit, costing $185. A friend last year junked a perfectly good Mazda 6 because the tranismission failed through lack on service.


#3

If the GM maintenance schedule only goes as far as the 90k or 120k interval, that does not mean that the truck is maintenance-free as after it passes those intervals. As Doc stated, your trans fluid needs to be changed every 3 yrs/30k miles (whichever comes first).

While you have probably done some damage to the transmission by skipping several fluid and filter changes, you may just get a few more years out of that transmission if you drop the pan, clean it out, change the filter and fluid, and then repeat this procedure in a few months.


#4

Thanks for the quick response. I’ve kept up all other aspects of maintenance, brakes, shocks, drive belt, etc. My hesitancy is the horror stories of other DIYer’s who have changed tranny fluid on older vehicles only to suffer tranny problems shortly theeafter.


#5

Those horror stories are mainly from people who didn’t service their transmission and then thought a trans service would fix it. And it didn’t because the damage was already done.


#6

One simple word…Yes…

transman


#7

Those horror stories are mainly from people who didn’t service their transmission and then thought a trans service would fix it. And it didn’t because the damage was already done.

100% true. If they had done regular fluid changes with filter clean or replacement it is unlikely that they would be having problems now.