Fried my TH400. Parts advice

After my car being back on the road for only a month the trans appears to have died a sad death. It wont shift out of 1st and when it does occasionally fall into 2nd it slips and bucks. It was already a 2nd hand trans with unknown history so I suppose it has done well.

I want to know if i'm on the right track with these rebuild kits. My budget is very limited due to shipping costs and exchange rates. The price for just stock rebuild parts down here is way too high.

This is the rebuild kit I was going to go with as it comes with a trans kit which is a bonus:

http://www.summitracing.com/parts/TCI-228800/

I understand that one of the main improvements made is a heavy duty sprag. Is this what i require?:

http://www.summitracing.com/parts/TCI-227900/

Now the big question. My car has a boss hog 3200rpm 10" converter in there which I bought sometime last year. It slips horrendously pretty much all the time which is probably what led to the death of the trans (it does have a cooler but obviously not enough). Too much stall and too cheap of a converter so now im looking for something a bit more suited to my driving.

The car is driven around the suburbs 90% of the time with around 9.9% highway use and would be lucky to see the strip once a year. It has the recently rebuilt 3.42posi in the back and the engine has mildly ported and polished stock irons with a Holley street HP 750cfm with dual 2.5" exhaust. It flows really well with a cam with similar specs to this http://www.taperformance.com/proddetail.asp?prod=TA_310-455 but with stock lift and idles at around 750rpm.

These hughes converters seem like good value for money so bearing that combo in mind would their 2000rpm or 2500rpm be more suited?

http://www.summitracing.com/parts/HUP-GM25/

Thanks

 

Matt, Im by no means a transmisssion expert but I do know heat and HP are the major killers of transmissions, I do know the sprag is one of the weak points in the TH400, I run a 2000-2500 Boss Hog stall in my GS and am very satisfied with its operation both Hwy and street, I would think for your application the transmission parts you have picked out will do the job just fine, depending on how heafty your cam is you don't want to go overkill on a stall if its only going to be used on the track a very small percentage of the time. Just my 2 cents worth. Im sure someone with more knowledge will chime in.

 

Yes, that sprag is a good investment.

Regarding converters, you can contact Jim Weise here http://www.trishieldperformance.com/ Here's info about his converters: http://www.v8buick.com/showthread.php?t=147066

Coan is another well-known supplier that will build a converter to suit your needs.

Devon

 

I'd imagine you already checked this, but is the modulator getting vacuum?

 

Spending big bucks on a higher quality converter is something I can't justify at this stage. I'm looking for something that would give me better than stock break-away without sacrificing driveability.

It seems that the 3200rpm that's in their now was stalling way too high for daily driving and just slipped most of the time. It sounded like a CVT where the engine would do 3000rpm no matter how fast you were going. It was probably just due to the weight of the car that needed to be lugged around.

Vacuum to the modulator was the first thing i checked p.

 

Matt, the problem is that when it comes to converter efficiency (which is what you're complaining about), you get what you pay for. A well built, efficient converter with tight internal clearances is what makes it perform so much better than a typical low budget off-the-shelf item.

Between two that stall at 3000 rpm for example, the well built version will behave close to stock at part throttle, while the cheap version is slipping immediately. It's a matter of saving up $300 and spending it now, vs saving up $500 and not being sorry or having to do another "do over".

Devon

 

while i'm aware of that, it's more a case of it either gets something that will be better than what i have or it's just going to get one of the stock ones that i have lieing around the garage put in it.

 

Regarding the rebuild kit, it would be good if you took the trans apart to know what it really needs. Lately I have found some pretty expensive kits don't include any torrington (should replace) or sleeve (probably OK) bearings, a vacuum modulator, filter, some other items, but have a pricey shift kit I don't need. For a small fraction I can get just as good a rebuild kit, but without the shift kit and without all the steel plates (that are practically always fine). Sure I still need some other pieces, at least there is some money left to buy them. The 34 element sprag is justified for some applications. If a trans is just suffering ancient rubber piston seals, a $32 kit will do the job. On the other hand, a burned up clutch pack could have spread crud everywhere including the torque converter. Bruce Roe

 

Thanks Bruce that's the kind of advice i'm grateful for :beer. The trans has already been split and disassembled by the builder. The sprag is actually busted and all the friction material is toast. The bands, clutches and steels all look very chewed. That is the reason for the full rebuild kit which includes all of those items.

My trans builder also mentioned the need to have the torque converter flushed to remove the spread out junk for that very reason. I see this as a time to replace it with something that i will find more suited to the driving I do rather than spend the money rebuilding the converter that fried the trans in the first place.

Because the car is not raced and I realize i went overboard with the stall on the converter last time this is the opportunity to get something that will do what i need it to. So basically what im asking is with a bloody heavy car with 3.42 gears and a cam that's advertised to make it's power 2000-5000rpm would i be better going for a 2000rpm or a 2500rpm advertised stall converter. They say that the big blocks will stall converters a bit higher than whats rated which is why I'm learning towards the 2000rpm but at the same time dont want it to feel toooooo "boggy".

 

i installed a 2200 stall th350 converter in my 70 wildcat
it was a cheap upgrade
the 350 converter will bolt in the th400

my car weighs 4600 lbs and the converter flashes to 2500 rpm out of the hole

just my 2 cents worth

scott

 

Cheers Scott. Sounds good, do you know if that was a 12" converter?

 

i think it was a 10"
but dont quote me on that
scott

 

matt,
it's a shame your car doesn't have the original switch pitch 400 , that would be perfect for what your wanting to do. Bob

 

Yeah, too bad the original transmission is gone. Otherwise, go with a 12" converter with a 2200 max stall RPM, 2000 RPM better. You need the diameter for it to feel right at light throttle in a big car. It would allow for just about as much cam as you would want in a fullsize. You'll love how it drives. Hi stall converters, even the high end ones, absolutely suck in fullsize cars. The cheap ones just suck even worse. I've tried several of the high ends ones mentioned on here and absolutely hated them at anything but full throttle. One tenth of a second quicker at the track, is not worth poor driveability and horrible gas mileage the rest of the time.

 

Stock vs Heavy Duty sprag....I just ate the sprag in my turbo 350 ...I say get the heavier one while your rebuilding it- good insurance ....:TU:

 

I appreciate what I'm getting back as it will really help be in the future. But the situation right now is I'm a 19 year old student and work 10 hours a week on minimum wage. 1 of my dollars is only worth 75 of your cents and even the smallest box costs at least $75USD to ship. I could have bought another Nissan Skyline and been like everyone else but i chose to be different so this is the price I pay.

I will go ahead with the rebuild kit and the sprag as some of you have agreed will work well for me. This will let my trans builder get on with putting the thing together so I have a box ready for the car.

As far as torque converters go the car is never raced except for the occasional stop light burn. Like David said the small diameter converters behave annoyingly in big heavy cars and I have definitely witnessed this first hand. It looks like ill go for one of the 2000-2200rpm rated 12" ones which should give better than stock performance without sacrificing anything else.

As always, thanks for the words of wisdom. Hopefully one day I will be able to contribute to people in situations like my own. :beer

 

Hey guys just got back from all my summer holidays and found my car still dead in the garage.

I don't really know enough about these things to be confident in what i want to order. In regards to the sprag specifically, I can't see it in the bin of parts I have.

The code on the box is 73-PD-76755

My immediate thought was that this is not the original transmission which is unfortunate. From some kind of 1973 Pontiac I presume?

Now what do I do in regards to this sprag. (I don't have any old style drums around).