Or pull your 904 and rebuild it yourself!!!! Rebuilt kit consisting of new clutches and seals runs right around $150. There is a 904 rebuild video on youtube thats gives you step by step instructions.
Assuming it has never been touched before, and just needs a simple rebuild of the clutches and seals, (most likely) you can do it in about 8 hours start to finish. Its not that difficult...just follow the youtube. Make sure you keep everything organized as you remove the parts.
PS...there are rebuild manuals from TCI that you can buy, but, they can drive you nuts talking about measuring tolerances and adjusting the sizes to get just right. IGNORE all of that and tear it down and reassemble and the tolerances assuming your using a factory style rebuild kit will be right on...
Tools you will need besides sockets and wrenches are a good set of snap ring pliers as there are many in there that hold things together, and a slide hammer to get out the front pump. You will also need a tool you can make to depress the spring on the clutch paks. I made one myself out of a long all thread bolt and a U shaped bracket. Biggest problem i encountered was simply dropping the transmission down (i used a simple floor jack, with a 12" square piece of plywood) and then getting the front of the car high enough to be able to slide the huge bell housing out from under the car. BUT if you replace the tranny you have those issues anyways !!
I appreciate the enthusiasm! however, this started as a drip and a front pump seal replacement. Dropped the tranny, replaced th efront pump seal.. Should we do anything else while it's out? "Nope", Installed the tranny, issued dropping into drive on the highway, advanced deducery with the kickdown lever employed. Lacked the advanced and deducery requirements.. Still leaked.. Looks like from the shift shaft seal.. Gouged the orig seal out of the car trans installed. Gouged horribly, ruined. Some guy at a tranny shop that had a new old stock shift shaft on his shelf in a 1971 box, shipped it to me for $50! Thanks for saving a spot on your shelf for 50 years for 50 dollars in 2021! Replaced the shaft, installed seal with slide hammer, destroyed. Next one installed with a delicate makeshift bolt slide hammer, success!! throw the valve body in there, assemble everything under master mechanic watchful eye, this time. Everything looks like it goes together right.
First run was the best run, only a small portion of the getting into drive. Each subsequent run, gets worse, and my fidgeting with the kick down lever makes it worse. Mechanic says check the governor, sometimes it can get impacted with debris. He told a story "I would not have beliueved it had I not seen it with my own eyes".. I guess back in the 70s, a solution was to be going down the road at some decent speed, throw it in Park while driving.. Because the vehicle is moving, the pins cannot catch, and it won't actually destroy it, but it will cause it to BANG, which does break free any debris impeding the governor. So I learn what a governor is, I remove the tailshaft (I think the way I learned how is watching the segment of video's you quote, the section they cover tailshaft removal. So I get that off, I remove the governor, and I cannot find any debris or thing out of the ordinary to impact it, and it appears to move freely.
After that my mechanic says well.. Since it seems like it warms up and gets worse, and since your governor is not the problem, it sounds like it's losing pressure and either it's a valve issue or you're losing pressure due to a failing pump. Oh, and I was losing revers, it slips terribly. We filled to level and that did not stop it. So he says you're at rebuild time. At this point there's no business testing pressures and diagnosing further..
So, now I'm like I don't want an automatic transmission anyway.. If I'm going to rebuild anything it'll be what I do want, and maybe something new, so I can stop wrenching and start driving lord knows the neighbors have seen this thing in the air longer than they've seen it on the ground..
