Catostrophic tranny failure on dyno

10secgoal

Active Member
Dec 1, 2003
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San Diego
Wanna talk about pissed off ?! It was supposed to good day. I was going to the dyno, right ? I was pissed off after the first pulls on the motor as it was. I was only getting 275 to the rear. The ft/lbs were nice numbers though. 369 at like 4800. The motor should have more, but I didn't want to be there anymore. I was quite pissed that I rented the dyno for the day and the people wouldn't let me tune the bloody thing the way I wanted. So I was just going to get some numbers and tune at the track. I had had enough of them. Then the starter went out. Good 'ol Autozone products. Lifetime guarantee does no good if all you have is a guaranteed piece of ****! Once I got it in I ran the bottle. It was like 8/1 on the a/f ratio. After fooling with everything and running it again it was at a better but fat 11/1. That was the last run. At about 6300 I felt a bad vibration. I let off. Too late!! I twisted the driveshaft into almost 3 pieces. Into two atleast. It looked like a twisted straw that had been cut in the middle. It got real bad when I saw the starter I just put, in on the ground. When the driveshaft hit the ground it toook out my exhuast, tailshaft,bellhousing,and at least one arp stud on my stall. I don't really even know yet. I haven't looked. I already want to sell the thing I'm so FN pissed, looking at it won't help. I only know what I know from the parts that were on the ground under the car. It did make 341hp and472trq to the rear on a 100hp shot though. :nice: The 175 was next. Guess I'll never know. The 8 in held up :rlaugh:
 
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Dude! So sorry to hear about your car :(

I've not had any big problems like that but anytime something terrible happens you need to walk away from it and stay away for a while, it may take a few weeks too.

D.Hearne said:
You gotta Love C-4's------ Every one I've ever had cratered, not as bad as yours though. Sounds like time to swap in a Toploader 4 speed. Or at least use an FMX.

That is the opposite of everything I've heard and read. C4s (when built accordingly of course) are living behind 1,000HP engines and many sub-9 second 5.0s are converting to them. But the FMX has had a bad rep since I've been in the hobby (about 1983). I know your expertise D, if that was not posted by someone with your knowlege I would have probably ignored it. Fill me in here please.
 
Well, all I can say is, Back in the 70's when the Cleveland was the hot thing to have ( instead of today it's the 351W ) Everyone knew that the transmission to have behind one was the FMX, this included the folks at Ford. Virtually all the 351C's that came from the factory had FMX's, I don't believe I've ever seen them equipped with C-4's. The FMX seems to have fell out of favor with the 351C, even though both were excellant. I had a 69 Econoline van that came with a 302, and a heavy duty C-4. In the 10 year time span that we had this van, we had to have the C-4 rebuilt 5 times. I pulled a C-4 from a 67 Stang to use in my 89 Ranger V8 swap, after 3 months behind a stock 88 Crown Vic 5.0, it too cratered. :bang: I have since switched to an ebay special-Toploader 4 speed and it's been there ever since, without touching it. :D I've got an FMX sitting in the shop that I pulled from a 71 LTD, that's waiting for a new home, and I've no doubts that it'll most likely work fine. Have another that's bolted to a 390 from a 63 Merc, that after a 5-6 year nap,wouldn't pull, but worked fine after adding 1 1/2 quarts of ATF ( so much so that it smoked the tires) Like I said, it's been my experience that any C-4 will leave you stranded , I just have no faith in them. I know that they've been built to handle lots of power, but you don't hear about them cratering when the power's applied, and I know that this does happen. Another tidbit to ponder: Why did Ford base the AOD on the FMX instead of the C-4 ? The C-4 evolved into the C-5 ( have one of those too, anyone need one? ) but went no further as far as what I've heard. You can ask anyone that has an FMX and you'lll rarely have them bad mouth it. Only drawback to them is the lack of aftermarket support, maybe it's cause they don't break parts as fast as the C-4? :shrug: And so don't require as many replacement parts? :shrug: Makes you wonder :nice:
 
67GTCOUPE said:
Guess you will be installing a driveshaft saftey loop?
Wouldn't have mattered here. Were it broke, it still would have hit the ground like it did and still broke.
D.Hearne. I heard that FMX soak up more HP than anything. Yeah I've heard good and bad of c-4's as any performance part. Although I can't really say that the tranny broke because of a weakness. Although a cast iron fmx probably would have taken it.
As for a top loader, that's what I was thinking. Or a tremec. A close ratio 4 speed would be nice though. But I really need a break. I'm seriously thinking about selling it all. But I would take such a lose I don't know if it is possbile. :shrug: Not to mention everytime I here an import or a car rev. I would just be another jack ass that says, "I use to have fast car, ran tens on radials." You know that type.
 
While I hate to hear the bad luck. I want you to think about this. That could have happened on the track or street. You may have broke a bunch of parts on the dyno. If you had did that while driving/racing the car, you could have been killed or killed someone else, not to mention crash the car. So its not all bad. I use to sort out the car in the driveway. It was a long driveway. That way I didnt have to worry about getting it home when it broke something. Remember too that stock parts arent made to stand up to extreme conditions. Stay away from rebuilt parts at the parts stores for racing. In my 30+ years of racing. I have broke things they said you cant break. And seen things that should have broke that didnt. I have learned not to cut corners. It cost more in the long run. If you live through it. Again sorry for the bad luck.
Bud

Hey Hearne: I will let you know how well a C4 stands up. I'm thinking about putting one behind the FE motor I'm building instead of the C6. Its one of those, you cant break it things..... :rlaugh:
 
stock for stock D's right, the C4's just dont hold up under heavy duty, or high performance settups. i have a C4 in my grand marquis(the original AOD apparently blew up and the PO replaced it with a C4) and it is holding up fine, of course my 302 is only making about 160hp right now. but the reason ford based the AOD off the fmx and not the C4 is because the fmx had more room for the o/d unit. properly modified C4's can handle up to 1,000hp. the C4 is a favorite of drag racers because it is light and has low rotating mass.
 
know quite a few people running c-4's behind 9 sec big blocks..
like connecting rods, it's one the places you cant skimp... was going to use a c-4 behind the 557.. decided to go with a 'glide..

BTW, I broke an FMX in two...

putting a stock trans behind a hipo engine is asking for trouble...

and keep at it.. setbacks suck... but the 1st time you really get on it.. heheh.. :nice:
 

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Dark Knight said:
know quite a few people running c-4's behind 9 sec big blocks..
like connecting rods, it's one the places you cant skimp... was going to use a c-4 behind the 557.. decided to go with a 'glide..

BTW, I broke an FMX in two...

putting a stock trans behind a hipo engine is asking for trouble...

and keep at it.. setbacks suck... but the 1st time you really get on it.. heheh.. :nice:
That FMX looks like maybe the transmission mount was loose, with the way it broke off at the tailshaft housing /main case junction. In that case, it wouldn't have been a design flaw/weakness, just poor maintenence
 
Man that sucks... just remember.. its a car.. it can be fixed.. save up some dough.. and get a lentech Stage 3 AOD.. or I think art carr c4.. i believe both of those have a if it breaks in the horsepower range we build it for its replaced for free.