FAQs About the TH400 Smart-Tech Drum Module

Here you will find a list of frequently asked questions we've heard from racers and builders about the Sonnax Smart-Tech drum module, 34555-01K. If you have additional questions or need assistance with the module, please contact our product support team.

Scroll down to view all or use these links to jump to a specific section:

• About the Module

• Performance & Safety Benefits

• Horsepower & Application Compatibility

• Transmission Parts Compatibility

• Setup & Installation

Who is the Smart-Tech drum module for?
It is for any drag racer who wants to improve the performance, consistency and safety of their TH400.

What’s included in the Smart-Tech drum module?
This all-in-one kit includes 100% new parts for upgrading the forward and direct drums plus everything else from intermediate sprag to back of the pump. See the complete module component list here. An input shaft is not included — see Sonnax options here.

Why is this so much more expensive than an aluminum drum?
While it is more costly than a single drum, the Smart-Tech drum module is a great value:

• All-in-one upgrade: Using an aluminum drum requires sourcing and buying a drum and the added expense of other parts for the larger sprag PLUS related parts (piston, clutch hub, etc.). With the module, you get 100% new, top-quality parts in one box (more than 100 pieces in all) to upgrade the entire forward/direct drum area of the transmission.
• Superior performance: Thanks to its unique design, the module improves vehicle performance more than aluminum drums.
• Superior safety: Unlike OE-style drum setups with direct drum components that can overspeed and explode, the module is at no risk for this problem. That is of huge value for the safety of vehicle and driver, especially in certain types of racing where stock TH400 cases are used.

Is the Smart-Tech drum module the same as the Kilgore Superlight?
The general concept of splitting functions of the direct drum, moving some functions to the input side, and as a result, reducing the number of components that counter-rotate is similar. In all other ways the Sonnax module is dramatically different — from massive clutch capacity and better internal support of components to 100% new content (no used core pieces).

How will the Smart-Tech drum module help me?
It delivers improved performance, quicker ETs, more traction/stability on the shifts and power to the wheels, plus greater durability and increased safety because there is no risk of drum explosion.

Will this make my car faster?
Users have seen measurable improvements with the Smart-Tech drum module at all power levels of competitive racing, from 500HP stock-type applications to 3,500+ HP no prep and pro mod vehicles.

How much ET will I gain?
Users have reported .015–.020 seconds with improvements in driveshaft speed and g-meter at onset, during and after both shifts.

TH400 drums are known to explode. Can this happen with the Smart-Tech drum module?
With OE-style drum setups, the forward drum is connected to the turbine in the torque converter and does not overspeed. The direct drum is mechanically connected to the gear train, and when there are other faults, it is the direct drum that overspeeds (a multiple of engine or driveshaft RPM) resulting in drum failure/explosion. Because of its unique design, the Smart-Tech drum module has no separate direct drum. There are still some module components connected to the gear train that are susceptible to overspeeding (steel shaft, clutch hub and separate friction plates), but due to their reduced diameters and mass, they will not explode and do not pose a threat.

Does the Smart-Tech drum module have centrifugal apply concerns?
Testing has shown that there are no centrifugal apply issues up to 9,500 RPM.

At what horsepower level should I consider using the Smart-Tech drum module?
Users have seen measurable improvements at all power levels of competitive racing, from 500HP stock-type applications to 3,500+ HP no prep and pro mod vehicles. Others are adopting it in applications with stock cases purely for safety reasons. Unlike OE-style setups, the module’s unique design prevents drum components from exploding and causing catastrophic transmission failure.

How much horsepower can the Smart-Tech drum module handle?
An upper limit is not yet established, but the module has run without issue in a range of race vehicles, some at 3,500 and 4,000HP. No testing has been done in lockup or diesel applications.

Can I use the Smart-Tech drum module on the street?
Yes, as long as there is no front band. The module is intended for drag racing manual shift setups with no front band. Units have survived drag and drive events with no issues.

Will the Smart-Tech drum module work in a 4L80-E?
No, due to its unique design, the module is only for applications that do not run a front band. The 4L80-E has the overdrive ring gear incorporated into the forward drum and typically still utilizes a front band.

Can I use the Smart-Tech drum module with a 2-speed TH400?
Yes, though there won’t be as significant an efficiency boost because 2-speed applications do not deal with direct drum counter-rotation in 1^st Gear and stopping the direct drum on the 1-2 shift. When using the module in a 2-speed application, however, there is still the benefit of lighter module components to pick up speed on the 2-3 shift, plus increased safety compared to an OE-style drum setup.

Is a 1-3/16" 27-spline input shaft available from Sonnax?
No. There may be other suppliers that offer one, but it must have a 28-spline configuration where it presses into the Smart-Tech drum module.

Is a lockup shaft available from Sonnax?
No. There may be other suppliers that offer one, but it must have a 28-spline configuration where it presses into the Smart-Tech drum module.

Will a Coan 29-spline input shaft work with the Smart-Tech drum module?
No. The input shaft must have a 28-spline configuration where it presses into the drum module.

Will the Smart-Tech drum module work with a Coan “big main” setup?
No. Sonnax has considered it and the current design allows for this potential to be developed, but a “big main” setup is not compatible with the parts available today.

Do I need an SFI-rated case to use the Smart-Tech drum module?
No, the module works well in stock TH400 cases.

Can I use the Smart-Tech drum module with a clean neutral valve body?
Yes, the module increases overall safety of clean neutral valve body designs, allowing them to be more like “safe” neutral valve bodies.

Do I need a clean neutral valve body when using the Smart-Tech drum module, or can I just throw the car in Neutral after a run?
No, a clean neutral valve body is not required. And yes, it is OK to shift to Neutral after a run with the module.

What core parts are required?
None. Assembly and installation of the Smart-Tech drum module do not require any used TH400 core parts.

What else do I need for installation?
You will need a stock-style intermediate clutch pack and an input shaft. Note: Most larger pro mod sprags require custom (non-OE) intermediate frictions, steels and backing plate. If the transmission was previously built with these, the builder will need to source OE-style versions of these components to install the Smart-Tech drum module.

Are spare/replacement parts available?
Yes. See the instructions here for a complete service part list. Some parts may be special order.

Is it necessary to use the rubber clutch separators?
No, it is builder’s choice whether to install them into directs and/or forwards. However, we recommend using them as they are a standard method for increasing overall durability and efficiency.

Does the Smart-Tech drum module require similar clutch counts and line pressure settings as traditional, OE-style drum designs?
This is largely dependent on the power and weight of the application, but generally, the module requires less clutch and line pressure than conventional drums.

Should I run high-energy frictions instead of those included with the Smart-Tech Drum module?
While there are a lot of friction options out there, the BorgWarner frictions included with module are recommended because they have consistent quality and thickness that make setup more predictable. Overall, the module requires less clutch and line pressure than conventional drums. Users have seen excellent results with the BorgWarner frictions up to 3,500+ HP and 9,000 RPM. If there are threshold issues, these frictions will give clear signs that can help identify other problems.

Does the Smart-Tech drum module require a bearing between the drum and center support?
No, the module does not require a bearing. It is compatible with radial thrust bearings at this location, and the module sprag shaft component can be modified to work with ball bearings at this location.