What kind of transmission do I have, what's wrong with it, and what's it going to cost to fix?

Just thought I'd ask.

But seriously folks: my '88 GMC 1500 has developed a pretty serious leak in the transmission, so much that it was slipping today before I added a quart of fluid. Not good. Trouble is, I'm not even sure what transmission I have in the thing.

Somebody (Bobzilla?) posted a link a while ago to decipher GM VINs, and I think transmission was included in the code. Can anybody help me out with that?

Also, any experience with these things dumping fluid would be helpful. It's pooling underneath the passenger side footwell, but I can't trace it to the source (lying on my back in the street).

What side is you dipstick tube on? The last GM I had with a major leak, the dipstick tube had pulled out of the case.

Ooh. It's on the same side as the leak (passenger side of the engine). I'll have a look at that.

Very fresh fluid, too. Translucent red and not stinky. Now I have to go through my records and see if it got rebuilt before I bought it.

It's a real *itch to see and reinstall if that's your problem. Good luck.

A big leak is probably something cheap and easy to fix, unless you like drove it over a boulder or something like that.

No boulders.

Turns out it's a 700R4, and it was indeed rebuilt, but that was 6 years and 60,000 miles ago. Guess I'll see if somebody can get it up in the air and poke around.

Up in the air? drive the front wheels up a curb, set the parking brake and climb under.

I say dipstick tube, shift linkage lever-deal input seal thingy (I make no claim of understanding ATs) or a major pan gasket failure.

motomoron wrote: Up in the air? drive the front wheels up a curb, set the parking brake and climb under.

What am I, a yokel? I have landscape pavers to drive onto. Sheesh.

motomoron wrote: I say dipstick tube, shift linkage lever-deal input seal thingy...

These are my primary suspects. Definitely above the pan gasket.

Any RWD automatic transmission for a truck will cost between $1500 and $2000 depending on what needs to be replaced. That's if it needs to be rebuilt.

I think the shift linkage is on the drivers side, but I'm not sure. On a TH350 the dip stick tube goes in the front corner about an inch above the pan gasket. It sticks down into the top of a ledge on the case. If my memory serves me right the 700R4 is based on the TH350 transmission and the dipstick is probably in the same place.

My Dad rebuilds automatics for a living in Central New York. He typically charges in the $1700 range for a 700 depending on what is fried.

Hmm, it seems to be dripping off the cooling lines, if that's what those are - 2 of them run low along the passenger side of the trans, right? And I had to un-clip one of them to get enough wiggle room to get the starter out that I just replaced a couple days ago...

So if it turns out to be the dipstick tube, what's the repair method? (Please don't say, "Step 1- remove transmission.")

Step one is disconnect the battery. Step TWO is remove transmission

Good news: it's just a pinhole in one of the cooler lines. Well, a 'pinhole' that's spraying fluid at the rate of about a half cup a minute at idle, but at least the replacement should be straightforward.

Now, where can I find a decent parts catalog for this thing? I'm striking out at Rock Auto.

How close to the fitting is it. I have replaced them with high pressure rubber lines before without any problem. Most after market coolers plumb with rubber. If my memory serves me right, the other option is a loner flare tool and some steel line from a parts house and bend your own.

I'm with Toyman, bend your own. If that's not possible, see if you can pull the cooler line and braze up the hole. Easily done with a MAPP torch, but you do need oxygen unless you want to die of old age waiting for stuff to glow.

Closer to the transmission than the cooler, but probably 6-12" from the fitting.

If I was going to go with rubber, I think I should do the other hard line, too. As rusty as it is, I'm guessing it's on borrowed time.

What parts have you used?

Woops. If it's that rusty, I wouldn't bother with rubber hose, you will wind up patching it all the time and one day it will spring a big leak, probably at highway speed and get fried meaning a pricey transmission rebuild. Hard lines aren't that expensive or difficult to replace. Sometimes creative rerouting can make it even easier. A big help is one of those cheapie tubing benders, like the one on the bottom in this pic:

I have one, it's not perfect but beats doing it by hand. They are like $3-$4.

Stop by your local parts house and tell them what you are doing. They should have the hose in stock. Use the stubs of the original lines as hose barbs. Or you could order something like this.

Jensenman's way is the proper way, mine is the lazy way. His will last longer.

I think I have a flare tool and bender from a brake job a while back. If so, sounds like I'll be bending some lines tomorrow.

While I'm at it (ie: involuntarily doing a transmission oil change), is there anything to the Max Life (etc) 'high mileage' transmission fluids? Or should I just run the regular Dexron stuff and forget about it?

tuna55 wrote: My Dad rebuilds automatics for a living in Central New York. He typically charges in the $1700 range for a 700 depending on what is fried.

I'm curious, where in CNY is he? I might have some busines for him, if he does manual transaxles.

alex wrote: While I'm at it (ie: involuntarily doing a transmission oil change), is there anything to the Max Life (etc) 'high mileage' transmission fluids? Or should I just run the regular Dexron stuff and forget about it?

That really depends on whether you do a full change (converter and all) or just the pan and filter. If it's just the pan and filter (you WILL change the filter while you're there, right?) stick with the Dexron. It's probably what's there, and it's just a few quarts. If you keep from overheating it, regular will give you lots of miles anyway. Why make it harder than need be? It's already a PITA, no?