Replacing an automatic transmission myself

The transmission in my wife’s 1997 GMC Safri has gone out and I’m considering buying a used one and replacing it myself. Can I do it myself? What are the pitfalls? How much does an automatic transmission weigh? What kind of adjustments will need to be made?

Sure! You can replace the transmission. But you’re going to need some basic equipment.

Jackstands to safely support the vehicle and to get it high enough to work under the vehicle and to remove and reinstall the transmission.

A transmission jack to remove and reinstall the transmission. The transmission can weigh 150 lbs.

An assortment of hand tools to remove the components that allow the removal of the transmission.

If it’s a 4WD, you’ll have to remove the transfer case before removing the transmission.

There are no adjustments involved as this is an electronic transmission. So it’s a plug-and-play affair.

So if you already have all the required equipment to do this, go for it!



Thanks for the encouragement. Its a rear wheel drive. Will a floor jack work? I do have most of the tools I need according to my Haynes manual.

Don’t use a floor jack. I did that once installing a transmission and the transmission fell off the floor jack pinning me under the transmission and the vehicle. I layed under there for almost an hour before the wife found me and jacked the transmission off me so I could get out. That Christmas she gave me a transmission jack as a gift. A transmission jack makes the job 80% easier.


Thanks again. I think I’ll take my cell phone under the van with me when I do this like I do when I go up on the roof to clean out the gutters in case the ladder gets blown down (actually happened to me once).

You can rent a transmission jack, worth every penny… Sometimes the transfer case comes out with the transmission, adding to the weight. Unbolt the torque converter from the flex-plate (flywheel) and take it out with the transmission, saving a BIG mess and possible damage to the converter…

Is your transmission really cooked?? Sometimes it’s better to have yours rebuilt or exchanged for a rebuilt one instead of messing with a used one…

Then if you plan on using a floor jack, at least consider using something like this. This will at least prevent the transmission from sliding off the floor jack.


I think it is. No reverse and 1st slips a lot. 2nd, 3rd, and 4th are still OK. I can get mine rebuilt for around $1270 but the used transmission is around $600 and we have a lot of debts and little money.

Do you have some buddy(s) that could help? Know anyone that’s done it? It’s a big job, manageable, but you gotta have a transmission jack.

Just a suggestion. Drop the pan and drain the fluid otherwise it can get very messy removing the trans. There are three places to watch out for where fluid will come from, one being the hole just above the pan where the dipstick tube inserts another place is the tailshaft housing where the driveshaft installs and the third is where the cooler lines attach to the side of the trans. Unless of course you have special plugs to plug those three places.


Get a friend or two to watch, really. Rent enough equip to get the car about 3 feet up at the best. You really need a jack for the trans. If you get ready and have help it is do able. It is not a one person job. Remember that you are trying to make the job safe first then save money. Doing it the other way is an er bill at best a funeral at worst.

I can’t believe 10 responses from our best members and no one has told you to be sure you flush the transmission cooler,better do it.

Not only that, but nobody warned him to check his tire pressure!

Seriously, that should be covered in his Haynes manual, and these guys can’t be expected to cover everything, can they?

Whitey, you won’t see instructions to flush the cooler in any manual (maybe a TSB) That kind of knowledge comes from experience. Instead the OP recieved repeated instructions on a jack.

What we’re faced with is a an unknown person who apparently hasn’t done this tough job before. I’m not worried about the fine points of him changing his transmission, I’m worried about him either damaging it or himself while doing a difficult job for the first time. Your advice is certainly worthwhile.