What are the options to upgrading to a stronger 700R4 Input Drum Assembly ?

I am rebuilding and upgrading my 1987 Corvette transmission with the auxillary valvebody.

After my own research and talking with transmission experts, with the latest modifications, you still have the factory input drum assembly to worry about failing under high torque loads.

Sonnex sells a press on reinforcement ring that goes onto the inside of Input Drum to keep the aluminum drum from splitting where the steel input shaft is pressed into. Some experts call this a Bandaid fix.

PATC transmissions is offering sometime in the future a Titanium metal Input drum for the 700R4's and 4L60E's. To replace the much weaker factory aluminum drum. No aftermarket steel input drums have ever been offered.

Read elsewhere of an individual using a 300mm late model 4L65E Input drum in his 700R4 trans. 4L65E supposedly being the strongest Input drum ever produced from GM for 1982 to 2010 700R4, 4L60E, 4L65E, and 4L70E transmission family. 700R4's like my 1987 trans use a 298mm drum assembly.

At this point, feeding much more than 300 horsepower and 400 ft./lbs of torque is just asking for big troubles. The input drum will fail at the splines, the aluminum shell will give away, or the steel input shaft will twist in 2. I seen a few failed input drums from 700R4's at my friends local transmission shop last week.

The most bullit proof option i am told is to use the old Turbo 400 trans with a Gear Vendors overdrive unit

I dont wish to install a GM 4L80E trans with a stand alone computer to control the trans shifting.

Perhaps Pete K. can shed some light on this matter ?

BR

 

I have never seen 1 failed drum, much less 2 in the same week.

If I had 2 input shaft/drum failures on my builds, under 600 ft lbs of torque, I would be looking to see what I did wrong on the builds.

 

I dont know how those input drums failed Pete. The input drums ripped apart/destroyed i seen recently. Maybe 5-6 grand neutral drops ? that will kill any transmission soon.

There is alot of complaints all over on the internet about the 700R4, 4L60, 4L60E input shafts and aluminum drum.

I did not have to search hard at all today.

Read a few from top trans experts around the country posted.

My local trans guy Jeff is lending a hand in the rebuild process of my 700R4. He asked me if I found a better input drum.

A Google search netted alot of complaints from all around on the aluminum input drum.

I havent broke my stock 1987 input drum. But it is a concern, spending money upgrading elsewhere, then having the input drum fail.

What do You do to the 700R4 input drum Pete for better durability ?

Run them as is if they pass a visual inspection?

Do You have them cyrogenticaly treated? Liquid nitrogen - cold hardening.

Or do you use that Sonnex press on ring to reinforce the input drum?

Or is it a trade secret ? lol I have run into that more often than not.

 

Careful inspection, and a sonnax sleeve if they are running spray or boost. The real secret to the drum surviving is the torque converter. Guys that try to run big power through a 12 inch converter have problems. I probably have more than 200 transmissions out there running more than 400 ft lbs of torque (likely closer to 300), and I don't see the problems you are describing.
If the problem was that rampant, I expect the aftermarket would not have waited 28 years to create an aftermarket input drum. Just my 2 cents.

 

I have heard that before too. Torque converter selection is key to making a factory input shaft live in GM transmissions.

A small diameter conveter takes the torsinal load off of the trans input shaft. Less weight and stored inerta energy the input shaft has to contend with and survive under.

Alot of people hate these 700R4 and 4l60E trannies from what I have read today. Including longtime Veteran transmission builders.

And many hotrodders I know dislike them just the same.

I allways enjoyed the quick and firm shifts my Vettes 700R4 trans delivered in the past. Till it finally failed under my heavy right foot on the gas for over 2 years. It lasted much longer than I ever anticapated.

Trying to avoid a ticking time bomb, taking extra TLC building this trans of mine.

I actually like this Corvette despite all the C4 nuicenses that go with owning them, driving, and repairing them.

Nothing beats the good old Turbo 400 trans for durability from my experience, just no overdrive !

 

Not sure why people don't like them. When built right, they hold up. I am not a professional trans builder, and I am not aware of anyone running my stuff suffering failures. My own car makes almost 600 ft lbs at the wheels on spray, and it doesn't break. Probably just jinxed myself, but if a dummy like me can build them successfully, I don't understand why pro's are having troubles.

 

I dont know why they are having problems either Pete.

At this point, I am going to rebuild this 700R4 as I see fit, to my standards and liking.

Too much Trick of the month parts and Gimmicks to buy and stick into these GM 700R4's.

And with some mild blueprinting and clearance checking as the GM 1987 Corvette manual shows how and my ATSG manuals show how to likewise.

I dont think you are dummy like you describe yourself to be from time to time in your posts. No man with 1st hand experience can ever lay such claim. Especially with automatic transmissions involved.

Thanks Pete, BR.

 

You have the right idea. Blueprinting, and careful selection of aftermarket parts.

 

I do plan to purchase one of those billet input drums, if they impress me. But only because I want to install a transbrake in my 700r4.

 

No one has ever mass produced a billet Input Drum for the 700R4, 4L60, 4L60E yet Pete from my recent research.

Maybe because of quality control problems, cost, and definatley this very bad economy. Cant sell enough of them to justify producing a large batch of input drums.

Steel would be the cheapest material to work with. But a few have said that it would be too heavy in weight. And then strain the rest of the transmission in operation.

Why General motors chose to make the Input Drum Main Body out of Alloy Aluminum.

There is also no center support in the 700R4 transmission family like the old Hydromatic Turbo 400. Heavy parts dont matter in the Turbo 400.

PATC transmissions has a small note on their website that they are going to release a Titanium Alloy Main Body Input Drum.

Sounds definatley Bullit Proof. But I know allready that it will be very expensive.

I have bought custom made Titanium Manley Brand Valves for my race engines in the past. $900.00 a set of 8. Thats for only the exaughst valves. Or intake valves. $1800.00 for a full set of 16.

There is a cheap titanium alloy that most race manufactures use.

Then there is a high end grade areospace grade titanium alloy used by the top manufactures use such as Manley Valves.

What do You think the price tag will be on the Billet Alloy Input Drum Or the Titanium Alloy Input Drum Pete ?

 

I spoke with the owner, Don at PATC when I dropped $1200 bucks on their custom ratio planetaries.

I can only guess, but I would expect the drum to run in excess of $1000.

 

Yes, I seen the custom planetary close ratio gearset they offered for the 700R4's and 4L60E transmissions. Cool Parts but Very Expensive.

Thats out of my Budget. LOL. My old lady would Kill Me. LOL

Shes here watching me type right now. lol.

She says I have to learn not to be so hard on the Corvette while driving it.

I tell her its so much fun though. lol

I have other cars I own that I can play hard with. And drag race if I choose to.

Muncie 4-speed equipped, and another with a Turbo 400 trans.

Just they dont have the same driving manners as my 1987 Vert has.

And everyone thinks that an old L98 Corvette will NOT run hard. I have suprised many in past. Including LS1 powered cars.

Do You sell any transmission rebuild kits Pete? Or reccomend any?

I am in the market to buy a kit.

I have my GM front and reaction 5 pinion planetary gearsets. Overkill as you stated in the past.

Hardened GM sunshell. New GM Reverse Input Drum. All GM torington needle thrust bearings.

Thanks, BR

 

I also have the 1 5/8" Long spline front ring gear hub and updated reaction tube hub assembly too.