Let me preface by saying I'm a complete transmission dunce, so please excuse my ignorance. The transmission in my 79 Bronco is going out, my buddy has one out of his truck that he wrecked, with a legitimate 5,000 miles on it. It has been sitting in his workshop for a year now, and has no torque converter. It's a 4x4 transmission that was bolted to a 400, perfect match for my Bronco.

Now comes my question(s)...because my head is spinning.

First of all can someone explain the stall speed for me please??? My 400 is mildly built with cam, headers, intake, etc...the typical bolt on stuff. I hop on O'Reilly autos website and I see stock replacements for $70ish. There are two, one with a stall at 1200 rpm, the other at 1600rpm. I hop on Summit, there are several more options. Some of the 4x4/offroad stalls that go upward of 3,000 rpm, and others less than that. So what is stall speed and how do I figure out which one I need???

Next question is...pilot hole. I thought on a 4x4 behind a 335/385 engine a C6 was a C6 was a C6...but I see a few different listings for pilot holes as well. My buddy's transmission was a relatively stock rebuild, so I assume stock diameter pilot hole is what I need...but what is stock size???

Last question...I also see different torque converter diameters...what's the difference???

Any help is much appreciated. Thanks.

 

So should I feel bad about myself because my questions are just that stupid, or is everyone just as lost as I am???

 

I can't comment on pilot holes, but stall speed is the engine rpms at which you start to deliver power to the wheels. Too low and your engine will bog down and always be pulling at a stop, too high and you really have to put your foot into before you start to move. It depends on your application and where your power curve is, but given your build you probably want the 1600.

Be patient, others will chime in.

 

Depending on cam rpm range. If your peak hrspwr/torque is lets say 4000rpm divide by 2. so a 2000 stall would be max converter i would use in 4wd application. so like mentioned 1600 would be a good place to start. If looking for fuel efficient lower your stall to like 1400 rpm. One of the by products of converter stall/slipping is heat, heat is bad! So if you are driving around and normal rpms in vehicle is around 2000 to 2800 you want your stall lower than normal driving conditions. In daily driver application/4wd wouldn't want to run a converter over 2200. making heat and if setting in traffic your just slipping and making heat and breaking down your tranny fluid. their is more to this conversation but this is the basic stuff. IF you install your converter yourself need to spin converter several times and make sure it engages the pump, you will feel it drop in place after spinning.

 

I would stick with a pretty low stall speed. stock or 1200 if you are just street driving and playing offroad. you can go higher if your engine makes GOOD power and you are racing it. ive got a 2500 stall in a race only half ton with a mild 460.

I think some of the early 460s had a smaller pilot hole in the end of the crankshaft. make sure you get a coverter for a 400/460, as fe series and smallblock both use different size pilots.

 

a lot of times diameter corresponds to stall speed. smaller diameter is higher stall. you may find that 2 with same stall speed have different diameters. smaller diameter will build more heat. larger diameter wont wrap up as fast due to more mass to get spinning.

 

Thank you all for the information. The rig is a trail runner/expedition style vehicle. Right at 325hp/400tq. The engine will wind out to 5200 but peak numbers are sub 3250. Not a mud pit truck, but it will clear out the 37" Boggers from time to time...but the majority of the time it's taking me to a trail or running an old two track.

I didn't mean to come across as impatient. At the time I posted there were 60+ views...so I assumed that either meant no one wanted to waste their time responding to stupid questions or they were in the same boat as me.

 

IMO there is NO such thing as a stupid question. If you don't know then it is a wise man that asks that "stupid question". No one learns by staying silent. That's how I am learning by asking questions... some may seem to look dumb to some that know the answer but to a guy that doesn't well you all get what I am trying to say. So ask your questions and learn. No doubt on some questions you WILL get a number of answers, others there is only one. Good luck and Happy truckin' John from Brussels Ontario, Canada

 

If you are buying a new convertor, Call the guys at hughes performance in arizona. These guys know there stuff and will get you where you need to be (weight,HP,)

i put in a towmaster XTM and am very much pleased.
XTM and XFM Series Converters

Chris

 

sounds like I would stick with a low stall then. stock or 1200 (which is probably pretty close to stock anyway.) for the price difference I would probably just go stock. but it wouldn't hurt to call and see what they say as mentioned above. you can never have too much information to help you make your own decisions.