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Old 08-09-2003, 09:43 AM
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TH 400 shift problem

I have a turbo 400 behind a mild 454. I have rebuilt this transmission twice with the same end result. It gets about 2000 miles a year. It has the b&m heavyduty street strip shift kit. First my tire chirping 2nd and 3rd slowly vanish then when i go to put it in reverse, there is a delay. Sometimes up to 5 or 6 seconds before it kicks into reverse. Fluid levels are where they should be. When I rebuild it it works fine for a season and ends up the same way. This trans should last longer than that. Any ideas?

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Old 08-09-2003, 12:44 PM
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Tires chirping when shifting may impress you, but it doesn't impress the trans. It is not designed to do that, and likely doesn't help your situation, as it causes pre-mature wear and break-down. It sounds like you either have a pressure loss somewhere from something broken or worn that you are not finding when doing the "rebuild" or the clutch packs are going together without proper clearance. Too much clearance will cause them to actually slip when engaged and burn up. Too little clearance will cause them to burn up by having too much friction on them when they are not supposed to be engaged. Some people believe that leaving some of the springs out of the drums helps it to engage quicker. Actually what happens is it dis-engages slower, as the springs are what releases the clutches. Like a manual clutch, the wear comes from engagement and disengagement, not the time in between.

Another prime example of why people should get professional help for transmission work. The people that sell the videos and books on DIY rebuilding have money at stake in the parts business. They are not and can not tell you everything you need to know to do the job right.
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Old 08-09-2003, 01:20 PM
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No springs were left out of the drum, this trans went together by the gm service manual specs with the only alteration being the shift improver kit. Professional help would be great if I had an extra 1000 bucks. I'm a diesel mechanic by trade and feel I should be able to figure this out. Any advice will be appreciated.
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Old 08-09-2003, 06:41 PM
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What did you find wrong at each rebuild?
What was done to the converter and cooler at each rebuild?
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Old 08-09-2003, 07:52 PM
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The first rebuild was my trans project in diesel school so everything was gone through. New steels ,clutches, front pump and the shift improver kit. I put a new 3500 stall in front of it and quickly found out it wasn't the best combination with a 3.08 gear and being solely street driven. Pulled it apart again (clutches burnt) replaced all steels and clutches flushed cooler and lines, replaced converter with a new stock piece and everything worked great for about 3 months. Now the delay going into reverse andthe shifts are softening up.
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Old 08-09-2003, 09:10 PM
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I would get rid of the B&M shift kit.

I built a th400 for a friend and added a b&m shift kit, it gave nothing but problems from broken intermediate race to broken low plantairies. Someone told me there is something about the b&m that breaks parts in a th400.
Me and a few other people have looked at this trans during it's several breakdowns.
Finally my friend got sick of the truck and sold it to me, I took the trans out set it aside and built another one with a transgo 1&2 kit, I loved the way that transmission shifted.
Later got around to disassembling the troubled th400 that was originally in the truck and found the forward clutch seals blown out. I think the pressures got a little too high from the pressure reg spring in the kit or something.

This troubled th400 is now in my nova with a manual valve body and a total rebuild and works great.

I also found the input shaft loose in the drum and a sticking governor valve.
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Old 08-09-2003, 09:36 PM
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BigBlock... Sorry, I didn't realize that a TH400 was a diesel. Being a diesel mechanic in no way would make you qualified to do my trans. Obviously it didn't help with yours either. The problem with trying to rebuild a transmission by a GM manual, or any other for that matter, is that it can't tell you what you will learn by doing.
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Old 08-09-2003, 11:19 PM
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Thanks yoda. There are a lot of parts on a hot rod that you don't want to work likethey did from the factory, it's not my daily driver and I don't want it to shift like it is. If you don't work on AT's every day, wouldn't a service manual be a logical place to get information?

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Old 08-09-2003, 11:26 PM
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adtkart......... remember these trannys are not voo-doo to work on.

so what if it takes 2-4 rebuilds to get the thing to work correctly for more than a few weeks. it is just a learning curve

I built my first automotive engine at age 15...... 34 years ago. Never built a diesel engine though. can't be much to it though.

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Old 08-09-2003, 11:53 PM
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On shift kits...

Keep in mind I'm not a pro trans rebuilder by any means like Crosley is, just a well-read enthusiast...

I have used both the B&M and the Transgo kits, on a trans in good MECHANICAL shape they work fine, as intended.

If the hard parts or seals are FUBAR, the shift kit will steadily make things worse, as most every kit will use boosted main pressure for clutch and band application.

A tire-chirping shift is GOOD, for everything but the tires.
The worst thing you can ask is for a TH-400 to shift long, gentle and 'lazy', like they come in a Cadillac.

If you can barely feel it shifting, that means there is an extended time period that the clutches/bands are acting slowly. Like slipping a stick shift clutch, the slippage puts excessive heat into the parts, that the fluid must carry away.

A quick, almost neck-snapping shift as provided by most of the kits in the strip-only mode means the slippage time is at a minimum, along with the trans-destroying heat buildup.

And yes, I have put many kits in GM trannies in the Heavy Duty/Towing mode, and gone back and stiffened them up more because I felt the HD mode was still slipping too much. Worst comes to worst you may have to buy another separator plate from a trans shop if you need to change from one kit setting to another...

Why do you think they ask if you're running an auxillary cooler? Heat is the auto trans enemy, every 20 degrees higher than 220 degrees shortens trans life by HALF. The fluid only needs enough heat in it to get rid of any condensation buildup inside the trans case. Any more heat than that and you can cook the clutches, warp the steels, and literally bake the internal seals in place. If necessary, get a fitting brazed into the pan and put a trans temp gauge on it, see just how hot it really gets.

Anyways, that's my take on this issue. I did not mean to step on any toes, just to report the facts as I understand them, and I tested to a 98% comprehension in school on stuff I read so I don't think I'm too far off on this...

Doc
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Old 08-10-2003, 08:35 AM
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Quote:
Originally posted by Crosley
adtkart......... remember these trannys are not voo-doo to work on.

so what if it takes 2-4 rebuilds to get the thing to work correctly for more than a few weeks. it is just a learning curve

I built my first automotive engine at age 15...... 34 years ago. Never built a diesel engine though. can't be much to it though.

Crosley... you're right. They are not voo-doo. Anyone that knows anything about an automobile, or anything mechanical, should be able to rebuild them and never have any problems. OOPS.... I guess that says something about the ability of some of these posters. Then again, I have never seen a book or video that explains how a mildly worn part feels or looks to a trained person. The examples I have seen are the extremes. Sure they don't work if they are completely worn out! They also don't work in performance applications if they are worn less in the right places. I guess that is knowledge that the average person should be born with. Unfortunately, I wasn't born with that knowledge. I had to learn it through training and experience.

I can see the advantage of the 2-4 rebuilds to get one to work right. Look at the experience you get, and the money saved. I know that the kits are free and no real labor to it! By the time you are done doing it that way, you definately know how to put one together so it won't work.

The part about chirping the tires only hurting the tires (not from Crosley) is a joke. That causes stress on the whole drive line, not just the tires.

Yes Crosley... diesels must be simple. They don't even have sparkplugs to go bad...
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Old 08-10-2003, 09:51 AM
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I never said...

that the driveline would NOT be stressed more. It stands to reason that the driveshaft and rear axle will see more stress under full-throttle use if it will chirp the tires on each shift. The tires become the limiting factor though, and a spinning tire is taking power from the trans and transfering it into smoke, not broken parts. Once the tire is spinning, it's coefficient of friction is less on whatever surface it is on, compared to it having grip. The shock loads on the driveline become higher, but tire grip is still the key factor, and we all know anything (pretty much) can spin the tires no matter how much of an underpowered dog it is otherwise (Yugo owners need not reply)...

If your car has worn out U-joints or a wimpy rear axle design it IS possible something is going to break. If that is the case then one needs to make sure the rest of the driveline is capable of handling the power the motor is putting out.

Where the shift kit helps the most is under part-throttle shifts. At these shifts (which happen probably 90% of the time one is driving their car on the street), the trans shifts just as quickly, but not as hard, simply because the engine IS at part throttle. The faster the shift is made, the less heat and wear is done to the trans hard parts.

Personally, I'd be pretty pleased to simply install a shift kit and find my otherwise stock vehicle now has enough power to bust a driveshaft or an axle. Those parts are much simpler mechanically than any engine or trans rebuild. FWIW, I have a Ford 8" axle in the '54 ford, behind a 500/TH-400. Yes it may break if I get on it too hard, but I can always find more 8" axles...

My '28 4x4 with a Cad 500/TH-400/Model 20 and 4.10 geared, welded 44's with 38.5 Boggers never busted anything in the driveline other than the wimpy 1.25 dia front driveshaft. I broke 2 of those, twisted the shaft itself into a pretzel actually, and that is a serious amount of torque from the driveline. Yes, I drove it on the street like that for 6 years. Tire slippage with the Boggers was always my limiting factor, I could smoke them pretty much at will. The axles should have been the weak link in this case, but it was the front driveshaft that was the off-road fuse. I could live with that, it was simple enough to re-tube the driveshaft if it did break. I only used the front drive part time, and only off road, the rear would get me home if it broke the front.

Take it as a joke if you'd like, makes no difference to me. I have always given advice/comments with the best intentions online, nobody says you have to agree with them.

But I DO know a lazy shifting trans will put more heat into the trans fluid than a firm shifting trans with a kit. That is a proven fact, not my opinion or conjecture. There are enough myths, opinions, and old wives tales out there that I will not aid in the continued passing-on of incorrect information...

Doc
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Old 08-10-2003, 10:50 AM
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Quote:
Originally posted by adtkart
BigBlock... Sorry, I didn't realize that a TH400 was a diesel. Being a diesel mechanic in no way would make you qualified to do my trans. Obviously it didn't help with yours either. The problem with trying to rebuild a transmission by a GM manual, or any other for that matter, is that it can't tell you what you will learn by doing.
I think you're going a little too far with this.
No one can predict a persons ability, especially if you don't know them.
I happen to be very good with most things mechanical, I've never had any formal training. I started with samll engines when I was 7.

Where I work I see guys all day long who have been through every class and every seminar and act like they work at nasa or something....And they still don't know jack about what they're doing. The only thing the training and certificates gets you is written proof that you know something about what you do and increase your chances of getting a job in that field.

I think some people are born with the ability to be better at some things then other people. Then on the other hand here come the guys with the book smarts. Natural ability is far better than book smarts IMO, the problem is you can't prove you have this natural ability over the internet or in a job interview.

Yes experience counts most, I've been given some very good advice that always worked from people on the internet who do it for a living.
This is what BigBlock69 is looking for, maybe all he needs is that one piece of information to get his trans right.
I have built many transmissions and a few have had one simple problem that gets me stumped and have come online and by providing a thorough discription of the problem recieved information to pull me through and get it right.

Crosley and others have helped me out a lot, never with an attitude problem, just a straight forward answer that works everytime.

And on the other hand come the people who think they need to degrade everyone. You need to change your ways or find another forum.

Quote:
Originally posted by adtkart
The problem with trying to rebuild a transmission by a GM manual, or any other for that matter, is that it can't tell you what you will learn by doing.
Heres a good example. I posted one time about a 700 I built by the manual, it had a bad 2-3 shift flare. Not only did I get a reponse telling me the manual is not the best thing to follow I also got advice on what to do to solve the problem .
Now tell me how you're helping.

I'm an a/c technican, does that mean I'm not qualified to build engines, transmissions and rearends?
I have built and sold quite a few of the above without any failures (except for the ones that want builds with inferior parts-which I don't do anymore).
I'm in the process of painting a full size, extra cab, longbed dually pickup truck and it's turning out beautiful. Never had any paint work training. And it's not the first vehicle I've painted succesfully.
Would you let an a/c guy paint your vehicle?

You need to stop judging peoples abilities, lose the attitude and try to provide some actual help.

Last edited by Jason; 08-10-2003 at 10:50 AM.
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Old 08-10-2003, 11:36 AM
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Jason.... If you read my post through and paid attention, maybe you would understand. Reading a book or looking at a video will not teach you how to spot the things that can likely cause problems, other than extremely worn or broken parts. If you are an AC technician, which you claim, and I can't/won't dispute, you should understand. There are things that you know from experience that are not in the books. Can you learn the difference in the noise of a bad ac clutch, as compared to a noisy compressor from a book? I don't think so, but can bet that you would know the difference right away. That is something that is learned by doing and training in the field, and can'tbe taught in a classroom or learned from a book or video. The same thing goes for trans work. The problem that I have is that there are alot of people here that are telling everyone that they can go out and buy a kit, at the tune of about $150.00 or so, take out their trans and put in the kit and everything will be OK. For some, that may work. For many others, it is going to end up being a big, expensive nightmare. I have seen times when trans have been rebuilt and not worked when done by experienced builders that knew their stuff. It was found later that the case had a crack that only showed up when hot. Lip seals for the drums are easilly cut during installation, even by the best.

Ideally, it would be great if someone could post a question on a transmission problem, and, with all of the information, they could get the correct answer to correct the problem with no cost. Now for the real world. Most problems can be caused by several things. It can be anything from a bad original part in the trans, to bad parts in the kit, to wrong assembly. Some of that can be checked, in the car, by a professional that has the tools and knowledge. So often there are people that are posting answers to questions when they know nothing about it. A common wrong response is to change the fluid and filter. I have seen people suggest changing the modulator, on trans that have none.

You think I've got an attitude, get over it. When you've done over 5000 transmissions, come back and we'll talk.
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Old 08-10-2003, 11:48 AM
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I think in adkarts world only Lingenfelter builds engines and only he builds Transmissions .

which clutches are burning up? all of them? how many clutches per stack are you using? did you rebush the trans on the rebuilds you did? did you go through the valve body 100% and check for valve galling and make sure everthing is moving freely? upon dissasembly of the trans on past rebuilds were the seals hard or cracked?

with this kind of info some conclusions can be drawn, if seals are hardening in a short period of time, high operatring temp is likely the issue, causing seals to crack or harden resulting in low apply pressures.

are you simply just over powering it? probably not because its ripping the tires free.

if the seals are in good shape, then assume there is a pressure prob, possibly from worn sealing rings, out of spec bushings or a worn out valve body.

i Have been told i am not a "PRO" but i do rebuild these things on a regular basis as part of my livelyhood and aside from the first few i did they all work very well and lasted very long.

i dont understand some peoples unwillingness to help people solve their problem, they would rarther make snide **** remarks and offer nothing usefull.
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