[ponyakr]

"...The stock factory hard parts in a T 400, 4L80E, will live just fine to 750 HP..."


Not for the sake of argument, but just to present my differing opinion, I don't think the factory int sprag or roller clutch that came in most Pontiac TH400's will live with that much power. I broke 2 of the stock 16 element sprags, with only about 400hp/500 torque.

My trans guy, at the time, installed what he called a 500 Cadillac sprag, in all my bracket TH400's, and I never broke one. I assume those sprags were about equal to the 34 element sprags used today, for HP TH400 builds.

[ta man]

I would think a slower et like a 11 to 13 second car would actually show the parasitic losses more than a 10 second or quicker car.

[Sirrotica]

Originally Posted by ta man

I would think a slower et like a 11 to 13 second car would actually show the parasitic losses more than a 10 second or quicker car.

Direct quote from Jakes Performance:

he 4L80E will theoretically consume more HP than a 4L60E or other lighter duty transmission. It has a positive displacement pump as opposed to a variable displacement, it is heavier, has more rotating mass, more clutch drag, and on the surface would seem to “eat” HP. The biggest loss would seem to come from the heavier rotating mass. However what is widely misunderstood is that yes it’s heavier, but that alone doesn’t cause more power loss. Remember an object in motion tends to stay in motion unless acted upon by another force. So unless there is more friction involved, a heavier rotating mass doesn’t take any more HP to maintain the same speed as a much lighter mass. It DOES take more power to accelerate or decelerate the heavier mass. So what this means to the average enthusiast is the faster your car, the more power the transmission will consume. This applies to all transmissions. Power loss through the transmission will increase the faster you accelerate it. Our testing has shown that you will not see any significant power loss in a 11, 12 or 13 second combination. They simply aren’t accelerating fast enough that the rotating mass really comes into play. As you get into the low 10 second ¼ mile times, you may start to see some differences between a lightweight transmission and a heavier one. The thing to remember is, typically the lighter duty transmissions become a maintenance item at these power levels. More frequent rebuilds and failures. So for a small loss of power often equating to less than .05 second in Elapsed Time in the ¼ mile, you gain reliability. Unless you are racing for a record attempt where hundredths of a second are crucial, reliability is usually a more important factor.

I'm sure Jake has plenty of experience with these transmissions to back up his statements.

[Sirrotica]

Originally Posted by ponyakr

"...The stock factory hard parts in a T 400, 4L80E, will live just fine to 750 HP..."


Not for the sake of argument, but just to present my differing opinion, I don't think the factory int sprag or roller clutch that came in most Pontiac TH400's will live with that much power. I broke 2 of the stock 16 element sprags, with only about 400hp/500 torque.

My trans guy, at the time, installed what he called a 500 Cadillac sprag, in all my bracket TH400's, and I never broke one. I assume those sprags were about equal to the 34 element sprags used today, for HP TH400 builds.

Also from Jakes Performance:

A totally stock unit or rebuild will typically live well with up to 450 flywheel HP/TQ. Above this point the direct clutches will not live long without some hydraulic improvements.
Using our modifications or some valve body kits, the direct clutch issues are resolved and the 4L80E will generally be reliable up to the 750 HP/TQ range unless it’s a very heavy combination (over 4500 lbs) or using nitrous.

The weak point above this power level becomes the OEM input shaft. An upgraded input shaft becomes mandatory. We like to upgrade the forward hub at the same time.

The next real weakness is the stock 34 element sprag. This part is actually capable on a well built unit of living at over 1000 HP/TQ BUT it requires care and knowledge by the end-user. Knowledge of proper burnout procedures is critical. It will also be a maintenance item at the 1000 HP level. It will need to be inspected/replaced occasionally depending on how the unit is used.

We recommend upgrading to a “Super Drum” style sprag that requires a modified or custom made drum and race. It has 36 elements that are wider, a larger race, and uses more intermediate frictions. If it fits in your budget, this is always an excellent upgrade above the 750 HP/TQ range. Combined with the input shaft and forward hub upgrade, it makes the 4L80E almost bulletproof.

Jake is probably in the top echelon of aftermarket performance transmission shops in the country. He does acknowledge that a sprag unit can break. The shafts, pumps, drums, and other hard parts will be reliable under 750 HP according to Jakes website. He cites proper burnout procedures as a longevity extender in either T 400 or 4L80E transmissions.