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How To - Tips => Engine & Transmission => Topic started by: dratts on September 09, 2012, 09:44:24 AM
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I'm so discouraged with my transmission problems. I apparently broke another input shaft. First one was stock. Second one was the 300m alloy. This one was the last GM Racing aermet 100 alloy available. I had wanted to dyno the turboed ls4 and run it through the quarter just to see what I have. Now I intend to just replace the input shaft with another 300m and just drive it carefully until I can figure it out. It's been in the garage more than it's been on the road ever since the engine install. I know that the Fiero guys have put the same amount of hp to the ground with their turbo 3800s. I have put over $10,000 into the turbo kit and built transmission. No problems at all with the turbo system.
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wow over 10k
expensive build
I thought this was the cheapest way to go.. hope you figure it out
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That doesn't include the original engine install. My goal was to equal the power and performance of the real deal, so that I wouldn't have to listen to those people who say "It's only a kit car". I have no idea what to do now. As far as I know there are no stronger input shafts or transmissions than what I already have.
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It is probably not so much the horsepower, but the torque. I was having the same kind of problem with my Porsche. I built a new motor now with a different torque curve. Less low end torque with more mid and high end. High horsepower low torque if that makes sense. That and no hole shots. It seems to be working for me.
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You gotta have something else going on ::scratch other than the power breaking the shaft. The odds of you breaking 3 input shafts in a nonracing situation is almost unthinkable.
Can you post up some pics of the other shafts where they broke? Are they twisting or snaping apart? If you put some pics up I will show them to a guy I know that used to be on a crew on a GM sponsered NOPI drag car. He is the man on performance FWD GM transmissions...
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What's the Dia of the shaft?
Some issues I found while researching transmissions comes down to bearing support within the transmission. Not having enough support allows the gears to push apart when you apply a lot of tq, which causes the shafts to bow. Normally it just breaks the gears but maybe your gears are strong enough and it's the shaft giving way. I think Jdinner made a plate for this issue..? The "Dinner Plate" ::study
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Did you consider having the shaft cyro-ed before you install it?
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It sounds like you are running a stock Fiero transmission. (Dinner Plate is for the Audi).
I believe this issue is caused by one of two things or both.
1) Is the clutch friction disc equipped with torsional springs? If not, replace it with one that does.
2) Are you trying to put down a patch of rubber?
Keep in mind you are now heavier, you have more rubber contact on the road and you are running more horsepower. It is going to break. This is not a matter of 'it might break' it is going to break regardless. You need to NOT shock the driveline.
Let the clutch out easy, get rolling and then hammer on it. It is the sudden shock that broke it and no person will convince me otherwise. I have seen it way too many times.
The only other thing it could be is a block of steel floating around inside the transmission that is jamming the gears.
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I should have been a little more clear. The current transmission is a built version of the 4t65ehd that came with the ls4. I started out with an isuzu hooked to a 350 sbc. My son in law broke that one. No surprise and no blame. The next one to break was the stock 4t65ehd input shaft. Replaced with a 300m input shaft and a 7/8" chain. Broke that one immediately. Next one was with a $1000 aermet 100 alloy input shaft and the built transmission from cartuning. It went when the torque converter let go and filled the tranny with debris. Then we cleaned the transmission out and installed a built torque converter. That was what I was running with a fresh tranny tune from cartuning when it let go again. I put the car away and haven't done anything yet out of disgust. I strongly suspect the input shaft, just because it felt then same as the last time it broke. Under hard acceleration, not from a stop when I lose all forward gears and reverse. Plan on replacing the input shaft with another 300m because there is nothing stronger and the. Just drive it with severely reduced throttle (like an old guy, which I am anyway) until someone can figure out what is going wrong. I know that Fiero guys are doing low 10 second quarters without all the mods I've done. They have to be putting down similar horsepower, but with a shorter wheelbase which should put more weight transfer, but 600 lbs lighter weight than mine. Anyway I will be back on the road soon with a lighter right foot.
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The previous shafts just sheared at the narrowest part. I appreciate the offer of your technical guys and I'll stay in touch when I get the tranny out again.
You gotta have something else going on ::scratch other than the power breaking the shaft. The odds of you breaking 3 input shafts in a nonracing situation is almost unthinkable.
Can you post up some pics of the other shafts where they broke? Are they twisting or snaping apart? If you put some pics up I will show them to a guy I know that used to be on a crew on a GM sponsered NOPI drag car. He is the man on performance FWD GM transmissions...
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The 300m and aermet 100 alloy shafts are far stronger than any cryo treated shafts. People are putting 600 hp through the 300m shafts with few failures and the aermet 100 was engineered for over 1000 hp.
Did you consider having the shaft cyro-ed before you install it?
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So, there is no chance of a misaligned input shaft?
When you say "built" transmission, do you mean it has a harsh shift kit in it?
If so, you might want to go with a stock shift pressure to reduce shocks.
Are you bypassing or doing something weird with the converter lock-up?
I find it very hard to believe that is happening with an auto trans.
Try a scrapyard transmission before spending any more money on it.
If you want to cryogenic treat it - send it to me, I'll perform the voodoo here and charge a fair price. (kidding of course)
Cryogenic processing really only helps wear, not strength. So the surface protection may improve but it will still snap under shocking conditions.
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Is it possible to misalignment the input shaft? Kevin at cartuning sold me the turbo kit and I sent the transmission to him for beefing up. It has a shift kit and an oversized piston for better clamping in third gear as well as better clutches and a few other things. He is going to send me more information, but he's leery of giving away his secrets, which I understand. We put a performance torque converter in the last time, but we had Kevins tune on it and I believe that there was nothing weird or bypassing done on the converter. Thanks for the suggestions!
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You have any pics?
I am interested to see this. ::thumbup
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I completly understand your frustration, kinda had the same situation many yars ago on a drag car I had purchased. I kept breaking the input shaft on a powerglide. Had it rebuilt 4 times and it kept breaking. Finally the trans guy said get a whole different powerglide, and he would build one from scratch. Sure enough I got one from a salvage yard, he built that one and I never had another transmission problem. Come to find out the 1st powerglide case was warped, dont know how it happened but under normal daily driving it was fine. Put some power to it and it would snap the main input shaft.
I know it sucks, but maybe you could just start with a whole different transmission core and start fresh. Good luck what ever you decide....
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I talked to someone who had a similar problem as TonyPaul described. The guy kept having issues with the seal around the output shaft. It was replaced 3 times under warranty on a brand new transmission. Finally the dealer replaced the transmission and sent out the original one to be inspected. Turns out that the bored holes for the output shaft and seal were out of round slightly.
So maybe that's your issue and it's causing the shaft to walk or bind, then break...? Maybe finding a new transmission case will solve your problems.
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I want to thank you guys for the responses I've gotten. I don't know if missalignment is the problem, but I for sure will look at it and take it into consideration. I was totally unaware of this possibility until you guys spoke up. Thank you again!
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I totallyagree with just getting a stock tranny on eBay and trying that
It's your lowest cost possible fix
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Here is a little more info on the problem with Don's transmission. The last input shaft broke when accelerating at more than 50 percent throttle from 20 ish MPH in third gear (trans in manual mode no down shift) Stall on the converter is stock but the converter is built. First shaft (stock broke shifting from 3rd to 4th at 90MPH, second shaft broke accelerating up an on ramp from a city street (gear unknown).
Pic of the Aermet 100 shaft
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That is not a load/impact/torque fracture of the shaft. They look really different when the hardened steel is broken under shocking torque. That looks like it was put on a lathe.
The load conditions you are describing will not break the shaft. I feel you have a poorly made transmission or serious problems with the housing.
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Yeah hardened steel usually busts into jagged pieces when fractured. The material pictured appears to be soft. Do you know a shop that could test the brinel/Rockwell of the shaft? Maybe they are only case hardened with a soft inner section...
Did the others break exactly the same?
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The first stock input shaft, the second 300 m input shaft and the third (this one) aermet 100 shaft all sheared in the same place. (where the o-ring fits). This one was different in that it scored the bushing surface and twisted the splined area. For what it's worth it was in a 25 mph zone and I might have been doing 35. So far there have been some people who blame the 3rd gear acceleration for the break. I do know that I should not have been in third gear for an acceleration at that speed. I am still surprised though. This was the input shaft that GM Racing used in their 1200 hp ecotech. I think that they did about 180mph in the 1/4.
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Just googled it. 6.75 at 206mph!
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I researched the transmission for a bit. It's only rated at 280 ft lb stock... You have done upgrades to it but what tq is your engine putting out?
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Just get a whole new (used) core and go from there. That transmission just doesnt want to live behind a badass motor in a badass car, it wants to live behind some old grandpa's Buick Park Ave.
I would see if I could get a lower mileage trans from a salvage yard and throw it in. See how well it holds up in stock form, then down the road rebuild it with some better parts. I wouldnt get a different trans throw a bunch of money at it, then put it in and then come to find out its something else causing the breakage....
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We haven't dynoed the engine yet. The turbo kit is supposed to supply 640hp, but I wasn't anywhere near that when it broke. The transmission was a 20,000 mile unit from Morads and I spent over $3,000.00 getting it built by car tuning, the same guy (Kevin) who supplied the turbo. I was totally surprised to see the twist on the splined section. At his point I'm starting to question if the heat treating after machining the aermet alloy was adequate.
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I just spoke with my trans guy about your problems, he said- inside your transmission case there are machined grooves around the inside of the case. These grooves are what hold these various large snap rings that hold in the clutch packs/steels/ foward drum/ect. More than likely one or more of the material around the grooves has gave away or just broke and is not able to hold down the cluch packs/ drum/input shaft/ect. Its kinda wallowering around in there and it will catch at a certin spot and just snap anything that isnt lined up...
Hope that makes a little sense~ He has my friend 700r4 on his bench right now that has almost the same problem. Someone tried to put some 200r4 parts into his 700r4 and it broke one of machined recessed areas. My buddy has a '32 Ford coupe replica that had a weak sbc 305 in it and the trans never gave him any problems. We just put in a brand new 383 crate motor in it and the trans lasted 20 minutes....
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I think that we need far more info if we are going to be of any help and we need more pictures. Was the trans completely torn down after the first shaft breakage? What did the trans oil smell like? Did the car slow down and then lose power? Did the car have a loud bang and then slow down? How much chaff in the oil pan? Any other trans parts showing excessive wear? Are any of the sprags showing chatter? Looks like a double gear engagement part failure.
Jim
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I would see if I could get a lower mileage trans from a salvage yard and throw it in. See how well it holds up in stock form, then down the road rebuild it with some better parts. I wouldnt get a different trans throw a bunch of money at it, then put it in and then come to find out its something else causing the breakage....
I agree, do it stock for now and see how it performs.
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We haven't dynoed the engine yet. The turbo kit is supposed to supply 640hp, but I wasn't anywhere near that when it broke. The transmission was a 20,000 mile unit from Morads and I spent over $3,000.00 getting it built by car tuning, the same guy (Kevin) who supplied the turbo. I was totally surprised to see the twist on the splined section. At his point I'm starting to question if the heat treating after machining the aermet alloy was adequate.
Do not know what your torque rating on the box is but I am using an Audi 01E box (6 speed manual) and that is rated to 450Nm torque. I was told in no uncertain terms at GT40.com that that is the ONLY box to go for. I suggest you look for such a box usually found on 2wd A6?A8 or S8's Prestige Motors in the UK sold me one.
As far as your pic of the broken shaft, I'm no expert but did you do any suspension lowering on your ride? If you did remember there is play on the shafts and if you cut the coils and drop the ride that play gets neutralized and can cause the shaft to ride (milling?)
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Wow! What a great bunch of responses and so many things to consider and discuss with my transmission guys. Thank you! Thank you! There is no place anywhere that I could get this much support and advice.
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I'm agreeing with jdinner. Replace trans unit. It really sounds like too many mods done to the trans and then you don't know which way to turn to fix the problem. I turned a Turbo-400 into a Clutch-Turbo once, added a reverse pattern valve body, accumulator piston flop, and front pump pressure boost. It worked but what if it didn't???? I think that I would have felt very much like Dratts.
Jim
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The first input shaft broke when it was in the original transmission engine package. Not entirely unexpected as the input shaft was a known weak point. The second (a300M alloy one) was a surprise to me as I only got about 15 miles before it broke. It shifted very hard and fast and I'm not sure if that had anything to do with it as I'm unfamiliar with performance automatic transmissions. We then did a $4,000 performance rebuild on another transmission and the first time I put horsepower to it I broke the last aermet100 alloy shaft that was available. I heard another opinion yesterday about the shaft alignment issue. So I've had two transmissions in the car now. How do I measure shaft alignment? Should I go back to the transmission that was part of my original engine transmission package. I was there once already with the 300M shaft. Should I go there again with a better tune for torque management? I'm back on the road again right now and driving it like a little old lady. The transmission seems ok except that the torque converter slips in and out of lock out with the slightest throttle variation. Personally I suspect torque management as the problem with the first 300M shaft failure. One of my transmission rebuild was due to a torque converter failure. I wish that I had been informed about the likely failure of that part. I would have installed a built torque converter with the transmission in the first place. I sure hope that anybody who follows me can benefit from my misfortune. I've spent close to $8,000 on my transmissions so far and all I wanted was to put my car on the dyno once with 15 lbs of boost to certify the horsepower, then run it throughout the 1/4 once to see what it would do. After that I wanted to feel the horsepower at 5-8 lbs occasionaly without beating on it and not worrying about breaking it. So far all I've got from my builders is "sorry about that, give me some more money and I'll fix it again".