tranny go boom. (sorta)

[3.0 van gogh]

About 5 or 6 months I sold my mini to a friend of mine who needed something to drive a bit cheaper on gas. I had rebuilt the trans (670) about 2 winters ago. This trans was a '97 out of another 3.0 Caravan which I Installed into the '95 (the original was totally toasted). All was going fine until today when he called and said that he was broke down on the side of the road. So I go to pick him up and I looked at the gear cover on the side of the trans (driver sd) and the upper gear is coming through the cover. it had started to grind a hole through the cover. Now I am trying to think what went wrong. Broken shaft in the trans or maybe the a retaining nut came loose. I remember when I was rebuilding the trans it was very cold in the quonsot building. Maybe the red locktight didn't hold. I really cant remember exactly but it seemed like the gear set part of the trans was perfect as far as tolerances. trans was still shifting perfect for all that matters. (not much). Always used the atf+5 fluid. Oh well, just wondering what could of happened after this amount of time. It gave little warning sounds or indications of coming apart. Is this a common prob that I could of avoided. Where did I screw up. Or just bad luck. (He doesn't drive like an idiot either).

[RoadWarrior222]

Well it's not unheard of for the output shaft to break, but usually only when there's north of 400HP going through it.

[Vigo]

The nut just came loose. It's semi-common on those trannies. That's why the later years incorporated a little plate with tabs that keep the nut from backing off, and a raised/bulged side cover to accomodate that plate thing.

When you put it back together, use those factory pieces to prevent a repeat, and dont be afraid to give that nut 'all of it' from your impact gun. I hammered those things as hard as i could back when i worked in a trans shop.

[3.0 van gogh]

appreciate the advice. I hope it isn't to fragged to go back together. I assume other gears would be able to fit (from other trannies). IIRC, there was some "cut off year" that separated the trannies. but My mind is fuzzy if that would relate to the gears. Would any 670 or 413 gears fit? Oh well, if it is too far gone, its not that hard to find another one. Who knows, I might end up with the van back, (horse tradin').

[Vigo]

Any PAIR of 670 or 413 gears will probably fit. Just stay away from the real early (like pre-86) stuff because im not 100% on if anything was different that far back. But there are lots of different gears with different tooth count to make different ratios, so if you only want to replace one you'll have to get the same tooth count, and if you want to replace both you would at least want to be mindful of any changes you're making to the ratio (these gears are after all the trans guts so they are basically part of the diff ratio. Transfer gear ratio X ring and pinion ratio = effective total diff ratio).

As far as a cutoff year, it depends what changes you're referring to. I dont think there is year where nothing swaps with anything else. But there is a difference between 95 and 97 trannies.. 96 was the first year of a new body style of the van which had a new transmission mount that bolted to the top of the diff area on the trans. Any trans that has 3 vertical bolt holes on top of the diff area is 96+, and any without them (3.0L trannies anyway) is 95 and down.

[RoadWarrior222]

The bigger 2.5 cars likely have the same ratios, so you should be able to find parts in an A413.

[turbovanman²]

Its probably the transfer gear nut came off, I had it happen once too, sigh. Those suckers are spec'd at something like 200 ft/lbs and like Vigo said, around 95, they have a locking mechanism to stop that from happening.

You can't just mix and match gears due to the different ratio's, count the teeth and divide to get the ratio. You should replace them as a set.

[Vigo]

Make sure to inspect the bearing race in the case for the gear that walked out. It may have put a bad pattern on that race which would mess up a new bearing in a hurry if not replaced as a pair (bearing + race).