Help Diagnosing 904 Issues

-
C

Creedmoor

Recovering Fordaholic
Joined
Sep 21, 2011
Messages
220
Reaction score
41
Location
Zillah, WA
I just started having some weird tranny issues. Car is a 68 FB with a mild build on an early ‘70’s 318. Bought the car with this setup so I’m assuming an early ‘70’s 904 as well. Car has always performed great, with no issues for 3-4 years until a few weeks ago.
Start the car up after a couple of days sitting and put her into reverse and … nothing for a few seconds then starts slowly moving. Read that this was just the converter drain back issue so I start it up in neutral and it takes care of that issue (never used to do it though). However, when I pull up to the stop sign about a ¼ mile away, stop, then give it gas … no moving…more gas and she slowly pulls out and then suddenly grabs. Since I’m giving it much more gas at this point, it’s a good jolt. This’ll happen every time I stop until everything is really warmed up. Like 10 minutes of city traffic warmed up. She also seems to not want to make the 2-3 shift at the right time unless I take my foot off the gas during this pre-warm time period. My gas mileage also seems to have worsened.

Appreciate any guidance. I’ve built a couple of motors so am not a mechanical noob but auto trannies still seem sort of magical. Even though I’ve been reading up and I sort of get it. Would adjusting the bands (front and rear?) help? That sounds kinda easy and I want to put a TF2 shift kit in there anyway – but thought I better figure this out first.

Thanks guys.
 
Adjusting might help, but it sounds more like the lip seals have gotten hard. Fluid goes past them and won't engage the forward clutch well enough to get reverse. This explains the 'slip' in first and reverse best. It *could* be something in the low/rev band, but it would have more effect on reverse than when coming to/leaving a stop.

Dropping the pan and doing an air test would probably help reveal if this is the issue, and adjusting the bands in the mean time probably wouldn't hurt. Don't be surprised if it doesn't have much effect.

As far as having to lift slightly to get the shift you want with 2-3, you may try adjusting the throttle valve (kickdown) linkage by a few turns. You can search for and read up on the procedure all over this site and others.
 
Could be as simple as a restricted filter and the old drain back issue. Run it in neutral before trying to get a gear or it will go quickly. If it is already drained for a filter service at least do the spool valve upgrade. These transmissions did not originally keep the circuits charged at idle in PARK and if it starts draining back you can burn up clutches before the air purges. The new spool valve kit will circulate the system in park which also allows you to check the fluid in park and will make sure you have fluid and not air in the circuits when engaging the shift lever.

vbpgimage.php
 
mgunner, got a part # for that spool valve kit?

I'm seriously thinking of rebuilding the 904 that's in the car now or one attached to a '68 318 I have sitting around. Both came out of a 68 Valiant described as running, but tired 'bout 15 years ago now. Since my FB is '68, I was thinking of building the 318 and stuffing it in. Tranny first.

Couple more questions, if you'll indulge me. What's the difference in '60 - '71 and '72-'98 904's? The overhaul \ rebuild kits seem to be listed that way. Also, the kits all seem to be "TF-6" flavors regardless the year. Are any of the upgrades you all suggested and a TF-2 shift kit part of standard kits?

Oh, lastly, printed (sorry I'm old school there too;) ) reference material seems to be limited to an ATSG book. Any good? Any others out there?

Thanks doods.
 
The ATSG manual is decent. It takes a lot from the factory service manual. Only thing is I like to set most clearances tighter than the factory specs. The later 904's had some upgrades that required some different seals and there are at least 2 different styles of thrust washers. The TF-2 kit is a real good kit. I use it on most torqueflite's I rebuild. If you use the TF-2 kit you don't need to buy the kit MGuner recommended because those parts come with it.
 
I would guess you went through the basics, yes?

Checking fluid level warm and in NEUTRAL?

Throttle pressure linkage hooked up and adjusted correctly?
 
Creedmoor said:
Thanks Fishy,
Any disadvantage to using a 68 tranny vs a mid-70's one?
Click to expand...

To be honest I'm not all that familiar with what they upgraded in the 904's but from your description I don't think there's any worries about using an earlier model. If you were running a stroker with a lot of power you'd probably want a newer model.
 
Bad Sport said:
I would guess you went through the basics, yes?

Checking fluid level warm and in NEUTRAL?

Throttle pressure linkage hooked up and adjusted correctly?
Click to expand...

Oh heck yeah I checked. I was really, really hoping I was just low on fluid. Linkage hasn't moved from where it's been working perfectly for years.
 
Creedmoor said:
Thanks Fishy,
Any disadvantage to using a 68 tranny vs a mid-70's one?
Click to expand...

Only thing i know is the front servo was updated around 72ish.....

1st time i bought a transbrake for a 904...the instruction recommended a 72 and newer...in fact it had what PN to use as the oldest one..
 
Thanks for the replies guys. I've decided to go for it. Ordered up an ATSG handbook and am doing some reading. I've rebuilt a couple of motors (some motorcycles too) and consider myself to be a pretty good wrench so I believe I can do a 904 successfully.

I need to secure a tranny jack and a kit. Any recommendations on what to watch for / avoid as far as rebuild / overhaul kits?

Also, any tips / tricks for pulling the tranny.

I'm sure I'll have more questions as this project progresses.

Thanks fellas.
 
When you get it apart you'll find out how many clutch plates the front carrier holds. It can be either 3 or 4 discs. While the 3 disc unit is adequate for light duty applications I prefer to have at least 4 discs and you can do it easily by using the thinner discs made for the rear clutch. The only caveat is the clearance may end up being too tight even with the thinnest selective snap ring and you'll have to have the pressure plate machined down. My local machine shop machined down 2 plates for me for $20, although I know the guy real well and he gives me a break. Also as I mentioned earlier the factory clearance specifications were as broad as a barn door. I shoot for .035-.040" for the rear clutch. .050-.055'' for the front clutch and total end play of .020" but find most of the time the closest I can get the end play is in the low .030 range even with the thickest selective washer. Once in a while you get lucky and get it tighter but even .030" is decent. Make sure and replace all the bushings and thrust washers. There are at least 2 types of thrust washers that I know of depending on whether it has aluminum or steel planetary gearsets so find out what you have so you make sure to get the right ones. When you get the clutch packs rebuilt stack them on the pump clamped in a vise and air pressure test each clutch pack so if one isn't sealed up good you find out before you get the trans all together. Note: you will have some air leak past the reaction shaft sealing rings that seal the front clutch no matter how well you grease them up. Don't worry about it as it'll be find under pressure. Once everything is installed in the case air pressure test the servo's and clutch packs again. Better to find out now than later that a seal didn't seal up. Use 30-40 psi for the air pressure tests. I'm pretty sure the ATSG manual shows where to inject air for the tests but if it doesn't let me know and I'll post pics of it.
 
fishy & Ted,

Thanks guys. Man the knowledge base here is phenomenal! I'll probably order up the 727 book and TF-2 kit from Summit. That should put me pretty close to the $100 free shipping mark. I hope can find something else to add to get me all the way there;)

Going to go put her up and see exactly what year 904 is in the car, pop the pan, inspect / clean the filter, adjust the bands and see if that helps.. Pretty sure it'll want a rebuild. Kinda excited to learn how to do this! It'll be like when I built my first motor. That was fun.

For just dropping the pan and a quick band adjust is it better to put all four wheels up or just the front?
 
Creedmoor said:
I hope can find something else to add to get me all the way there.

I can think of a few things I need. :D

Kinda excited to learn how to do this! It'll be like when I built my first motor. That was fun.
Click to expand...

Let me know how that goes, I too will be wandering into that dark territory.
 
Bad Sport said:
Let me know how that goes, I too will be wandering into that dark territory.
Click to expand...

If you're referring to rebuilding your transmission don't be afraid. I just rebuilt my 904 last month. It was the first time I was ever inside a torqueflite and it was real easy.
Take your time and a digital camera during disassembly is your friend.

Ted
 
You asked about differences in 60s and 70s 904s. Somewhere in the early 1970s they changed the valve body to provide part throttle kick down. Until then you had to actually floor the car (push the kick down lever all the way) before it would kick down to a lower gear. The part throttle sure makes it better and more fun to cruise with. The valve bodies are interchangeable so all you need is one made after the upgrade.

Anybody know when they made the change?
 
DusTed74 said:
If you're referring to rebuilding your transmission don't be afraid. I just rebuilt my 904 last month. It was the first time I was ever inside a torqueflite and it was real easy.
Take your time and a digital camera during dis-assembly is your friend.

Ted
Click to expand...

Thanks, yeah everyone says they are. Never having been in one makes me wonder, lol.
 
str12-340 said:
You asked about differences in 60s and 70s 904s. Somewhere in the early 1970s they changed the valve body to provide part throttle kick down. Until then you had to actually floor the car (push the kick down lever all the way) before it would kick down to a lower gear. The part throttle sure makes it better and more fun to cruise with. The valve bodies are interchangeable so all you need is one made after the upgrade.

Anybody know when they made the change?
Click to expand...

I think it was 71
 
Quick update with a couple pics and a couple (well, a few) questions:

First, does it ever stop dripping? Going for two days now!

Look what I found in the pan-hope it means they took pride in their work.

The numbers on the edge of the pan area say it’s a ‘71 (motor is a ’77). They are:
3515852 3511 4055. Can someone verify my research? So this means I don’t have the part throttle kickdown VB which was used starting in ’72. Any idea on what an updated VB costs? I think you can use any from a 904 up to whenever they introduced the lock up converter – mid ‘80’s?

Picked up a filter / gasket kit. Came with two different gaskets. I’m guessing for both a 727 and 904. The filter is much larger than what was in the car, and with one less hole. Don’t think it matters as the mounting holes and “dog ear” are the same. Bigger is better right?

One concern is that I have no idea what fluid is already in there , so I picked up 6 quarts of this stuff. Think I’ll have any issues?

Pan had no debris and filter looked OK but kind of dirty (if its been in there since ’87 - to be expected. Here’s a pic of that. The red particles were picked up in the trash can.

I adjusted the rear band to 72 inch pounds (hard to read the dang scale under there with bi-focals!), backed off 4 turns and locked it down. Really seemed like I ended up turning in the adjusting screw way past where it originally was. I’m so hoping this’ll solve my 1st gear issues. Much as I’d like to tear a tranny apart, I really don’t want the part where you have to get it out of the car!

Appreciate all the guidance and advice.
 

Attachments

  • pan.jpg
    27.8 KB · Views: 153
  • filter size.jpg
    50.4 KB · Views: 144
  • dirty filter.jpg
    42.5 KB · Views: 126
  • fluid.jpg
    42.1 KB · Views: 130
You are correct that a 3515852 is a 71 trans. 71 had the part throttle kickdown but who knows if someone swapped out the valve body with an older one sometime in it's 44 year old life. That's the problem with stuff that's been into, you never know what got swapped.

The filter you bought is fine. The old torqueflite's that had a rear pump needed that extra hole. Yours doesn't have a rear pump. Unless they had synthetic fluid in it the fluid you bought is fine.

Even if the rear band did not operate at all it would still engage in first gear just fine. In fact the rear band does not engage in first gear unless you pull the shifter down into low. If reverse worked the rear band was doing it's job.

I hate to tell ya but IMO your still going to be yanking it out for a rebuild because I agree with Phreakish that the problem is most likely hardened lip seals in the rear clutch pack. I've been rebuilding torqueflite's since I was 17 (now 51) and every time I've had one do what you describe it's a rear clutch failure

Dropping a 904 is a piece of cake. Be glad you don't have to do a 4L80 in a 1 ton GMC van. When I was young and dumb I bench pressed one in place to show off to the guys where I worked. Paying for it now :banghead:

BTW here is a picture of the part throttle kickdown module and another of where it's bolted to the valve body. This should help you identify if the valve body has it. IMO it's the least of your worries though
 

Attachments

  • Part throttle kickdown module.jpg
    9.7 KB · Views: 145
  • Part throttle kickdow module location picture.jpg
    23.7 KB · Views: 160
Thanks fishy,

Cool, I looked and I do have the part-throttle kickdown VB. Hmm, I guess I wrongly read where the rear band was applied in low even when in D and starting from a stop. So, the question is: Do I waste $25 in tranny fluid and a pan gasket to find out I still have to pull it?

I have dual exhaust with H pipe. Do I just unbolt the downpipes from the manifold, disconnect the rear hangers and lay the whole system on the ground (still wrapped over the rear axle) and pull the tranny out the front? What's the best method?
 
I have an H pipe on the Dart but it still allows me to drop the tranny. Just have to nose down extract it after sliding it back a bit. I do have to drop it at the lead pipes for room.
 
The fact is that H pipes aren't always in the same location from car to car. It's usually a compromise where they end up. That being said you may or may not be able to sneak your tranny out with it in place.
On my car I'm unable to do that so I take the pipes and mufflers completely off the car. I left the tail pipes in place. This way they're out of the way and you have more room to move around. Plus if you're going to use a floor jack to raise and lower the trans you'll want as much floor space as possible. if you leave the pipes hanging down you just know that they're going to get in the way.

Ted
 
Did I mention that my exhaust is one piece, welded two and a half inch all the way back. Hate to have to cut it. Picked up one of the HF's scissor tranny jacks for $80 with a coupon. "Low lift " my a$$. All the way down, it's still 7 and half inches tall - not counting the ginormous ratchet strap buckle. I don't see that abortion fitting in the tunnel with the tranny. How do you guys do it?
 
You must log in or register to reply here.
-

Back
Top