lmt0705

iTrader: (7)

do you think its a neccesity to have a hardened input shaft in a 4l80e in a car making 800 rwhp. some builders say yes and some say no.

supermouse4

Most definitely, it is cheap insurance for protecting your transmission from damage that your motor is putting out horsepower wise.

It is a must in my book.

355TurboLT1

iTrader: (11)

Carl Rossler seems to think so and I tend to agree. Many circles consider 750 ft pounds of torque to be its limit. Im going with a forged input as well as intermediate shaft. Out of all of the parts the direct drum is the weakest link. Check out this link from ck performance.


http://www.ckperformance.com/resourc...OMPONENTS.html

built408

iTrader: (10)

I think anything over 600rwhp is a gamble on a stock shaft.

Firechikn

iTrader: (15)

I've ran the stock one for a while now. No problems. That would be in the 950 lb torque range.

slow67

iTrader: (2)

The direct drum is not a weak link. Your thinking of the intermediate sprag that attaches to the direct drum. Also with a proper build, the 34 element sprag should be good for 1000hp.

355TurboLT1

iTrader: (11)

According to Rossler both in stock form are not good for 1000hp. If you think its good go right on ahead. They have seen them explode. The 34 element sprag replacement as I mentioned, does not completely address the issue with a turbo car making that kind of power. I decided to avoid the half assed approach many buiders take and went with the best.

slow67

iTrader: (2)

I have a good friend that has been building high perf TH400s for 15 years. He says they are good for 1000hp. Hes even had them in a 1400hp 10,000lb monster (Airborne Ranger) and it lasted twice as long as the build before it (4 weekends instead of usual 2) with stock stuff.

BTW when you get the upgraded 36 element sprag/race/drum assembly it is the stock drum machined, so the drum isn't the issue (unless you are getting an aluminum drum).

lmt0705

iTrader: (7)

your friend said the shaft and the drum are good to 1000hp?

slow67

iTrader: (2)

And I quote:

https://ls1tech.com/forums/12515810-post16.html

355TurboLT1

iTrader: (11)

So you are saying the stock modified drum is stronger than the billet aluminum drum with steel insert. Man you need to do your homework on 4L80's. I think Rossler knows a bit more than your "friend" does. Do some research on the drums and what HP they can have problems regardless of the sprag upgrade. This is from a PRO in the industry, not "some Guy". I really could care less about internet opinions.

To the OP, if you are going over 800hp i would upgrade the drum and the input shaft. The intermediate is good up to 1000hp and usually is not an issue. Look at what others are doing (besides ls1tech.com) and make your decision. Call Rossler and a few other builders and get there reasoning. The torque is obviously what kills things and a turbo car will have plenty of that. Good luck.

lmt0705

iTrader: (7)

im getting answers on both sides of the fence here, all from reputible builders. I dont think even if I maxed my F1A I could get to 900 rwhp. maybe 820 to 850 range, however the car is pretty heavy. I just spoke personally with my local transmission guru who builds everything from slightly modded trannys to stuff for 6 second cars (including his own) and his opinion was the input shaft is more than up to task. he believes I need a 36element sprag. would there be a difference in abuse between a supercharged and a turbo car? I would think theres a lot more torque off the line in a turbo car.

355TurboLT1

iTrader: (11)

Once you approach 800-900 ft pounds I think it becomes more a function of motivating that already heavy car that kills this stuff. A much lighter car with the same power not be such an issue. Some guys have had trouble free use at these power levels, but remember there are so many different variables here. My opinion on this is yes, guys have been to this power level and have not had too many issues(that we know of), but would you skimp out on a forged motor by resusing the stock crank(when you know its questionable) just because it "might" hold the power you are putting out? If you plan to stay at or below 800hp you will most likely be just fine with a forged input shaft. It's cheap insurance. Some top builders believe modifying the stock drum and incorporating the larger sprag is a bandaid approach to fixing the real problem.

Like I said, call Rossler and discuss your setup. None of us besides the rebuiders themselves can make any good recommendations on what you should do. This is all specualtion. Call the sponsors here as well. Then make your decision. Did you look at ck perfomance???

slow67

iTrader: (2)

I never mentioned aluminum drums. And yes, the aluminum drums are stronger (in a way), but only has 1 purpose, to reduce rotating weight. This *can* possibly cause a hp gain, as well as be safer *if* you think you absolutely have to throw it in neutral at the end of a run.

Most of the upgraded sprag/race/drum assemblies use the stock cast iron (albeit machined) drum, which really has no hp limit. The only limit is rpm.

Until recently, you could only get the aluminum drums in solid aluminum and teflon seals would wear them after a few thousand miles. You also can't use the intermediate band with the aluminum drum.

This info is from someone who makes a living building performance transmissions.

And yes, he has had many conversations with Rossler, Chris @ CK, Hughes, etc over the last 15 years.

I have personally seen broken input shafts behind STOCK 6.0Ls (they were towing)

If you plan to max it out, I would go with the billet input shaft, intermediate shaft, upgraded sprag (900rwhp in a stalled auto is approaching 1100fwhp or more) and forward hub.

355TurboLT1

iTrader: (11)

You did mention them. "BTW when you get the upgraded 36 element sprag/race/drum assembly it is the stock drum machined, so the drum isn't the issue (unless you are getting an aluminum drum)." Some have had issue with the hub. I know all about the RPM issues, but they do break in other situations and there are better options. I'm happy I went with Rossler.

Most "get away with" just upgrading the input shaft. I believe in building it right the first go around. Its also a money issue for some people. I dont mind dropping 5k for a transmission thats been thoroughly thought out and proven in high hp applications. We all have our own idea of how to do something.

jakeshoe

iTrader: (14)

Since I was brought up in the conversation I will add to it..

TH400,
Stock input shaft and smooth (early or 4L80E) drum with 34 element sprag is good to approximately 1000 HP.

The 34 element sprag will actually go higher IF properly prepped. This requires doing some work on the center support, drum, and in some cases the forward hub.

Cast iron or aluminum material on the drum doesn't matter. The stock cast iron drum will take 1500+ HP. I've seen it done numerous times and I've done it myself. RPM is a killer of it.
That is why you do not shift to neutral at the end of a run, but that's another discussion.
If you are spinning more than 7500 rpm across the traps, put an aluminum drum in it for safety.

Aluminum drums are a maintenance item, even with the steel sleeve in the bore.
The drum drives the reaction tube by the splines broached into the center of the drum.
Even a properly machined, heat treated, and hard anodized aluminum drum will eventually see spline wear or in many cases the inner sprag race will start to spin on the drum.
These are usually pinned in place and there is only so much material there to pin it.
When you take into consideration that the drum comes to a complete stop everytime the trans shifts to 2nd, and the inner race sees this load, you can understand why they fail here and are a maintenance item.

One advantage of the aluminum drum is they are lighter and shock loading of the sprag is reduced on the 1-2 shift.

The TH400 input shaft is robust and holds up well. I've seen stock ones take over 1500 HP in a 10K lb monster truck. I wouldn't advise that, but it has been done pretty often.
I think the extremely low gearing helps in that situation.

If a person had a turbo combo in a normal weight car at or around the 1000 HP range, I would give them the option of stock or billet.

The same car but a N2O combo, I would want to use a billet piece because of the torque spike.

The stock forward drum is broached to accept the input shaft, the splines in the drum usually fail before the shaft itself.

Aftermarket input shafts can bring on their own set of problems in a TH400 as well. The lube circuit passages are smaller and this can kill engine thrust bearings in some cases.
There are ways to work around this but it's something to be aware of.

4L80E:
Stock input shafts are questionable. They occasionally break in stock 6.0L applications.
I agree that the 750-800 HP/TQ range is a good one to consider the billet shaft.
If money were no object I would install a 36 element drum in every TH400 or 4L80E I built.
However when you add a $500 hit to an already expensive transmission (the drum costs more than that but I deduct for the 34 element setup), most guys just can't justify it when the 34 element (properly prepped) will take over 1000 HP/TQ.

The ideal situation would be for someone to make the direct drum and reaction tube all one piece, but that's also wishful thinking that is a bit deeper into the theory than I care to discuss online.

Carl Rossler is one of the industry leaders, he has earned that reputation. I don't care to try to discredit him or his business in any way. However he isn't the only builder who can build a killer transmission.

There are quite a few of us who specialize in performance and racing transmissions and can build an equivalent product, but it's a pretty small industry and many of us talk amongst each other. I was on the phone for over an hour today with another very well known performance transmission company owner talking shop.

I will say it's normal business practice to "upsell". The slightly greater profit of using more "fancy" parts drives the upsell.

I also see a trend online for people to argue what they bought, whether they have any real first hand knowledge of even understand the fundamentals of whatever the product is, they argue to do it their way, because they have to justify their purchase to themselves.

I keep my screen name fairly low profile so I may be just "some guy" but I have TH400's, 4L80Es, and other GM units out there living quite well at elevated power levels and a good enough reputation that I stay busy.