Automatic Transmission Treatment

Forte Automatic Transmission Treatment

Harsh gear
changes in your
automatic?

Automatic gearboxes rely entirely on clean fluid to shift smoothly. When the fluid degrades — jerky changes, slip and delay follow. Forte ATT smooths operation and protects all automatic transmission types — DSG, conventional auto, Citroën LHM and more.

Order — £20 → How it works
★★★★★
£20 · Free UK delivery · No draining required · Compatible with all automatic transmission types
Forte Automatic Transmission Treatment bottle — smooths harsh gear changes and protects all automatic transmission types
Active diagnostic alerts — is this your gearbox?
💢
Harsh or jerky gear changes
Gear changes that jolt or feel harsh rather than smooth indicate degraded transmission fluid that has lost its viscosity and friction modifier chemistry — the properties that control how smoothly the clutch packs engage.
Forte ATT can help
⏱️
Delayed engagement in Drive or Reverse
A pause or hesitation when selecting Drive or Reverse — particularly when cold — indicates degraded fluid that has thickened and cannot build hydraulic pressure quickly enough for immediate engagement.
Forte ATT can help
📉
Slip between gear changes or at speed
The engine revving without a corresponding increase in speed — slip — indicates clutch packs that cannot grip correctly due to depleted friction modifier chemistry in the transmission fluid.
Forte ATT can help
Active diagnostic alerts — mechanical symptoms of automatic transmission fluid degradation including harsh gear changes, delayed engagement, slip between changes and fluid foaming
The pathology of failure

Why Do Automatic Gearboxes Develop Harsh Gear Changes?

An automatic gearbox is a purely hydraulic machine. It has no mechanical linkage to the driver — every gear change is controlled entirely by fluid pressure and fluid chemistry. When the fluid fails, the gearbox fails.

Automatic transmission fluid does multiple jobs simultaneously — it transmits hydraulic pressure to engage gear changes, lubricates all moving components, cools the transmission and controls the friction characteristics of the clutch packs. Every gear change relies on precise hydraulic pressure delivered by fluid of exactly the right viscosity.

Over time and mileage the fluid's viscosity improvers break down, its friction modifiers are depleted and its anti-wear additives are consumed. The fluid thickens when cold and thins excessively when hot. Clutch pack engagement becomes imprecise — gear changes feel harsh or are delayed. In severe cases slip occurs as the clutch packs can no longer grip correctly.

Extended service intervals — or transmission fluid that has never been changed — accelerate this degradation and are the most common cause of automatic gearbox problems on high mileage vehicles.

The pathology of transmission failure — showing how automatic transmission fluid degrades over time, losing viscosity friction modifier and anti-wear properties, causing progressive deterioration in gear change quality
Mechanism of action — engineered intervention. Showing how Forte Automatic Transmission Treatment restores viscosity friction modifier and anti-wear properties to degraded transmission fluid to smooth gear changes and protect the transmission.
What it does

What Does Forte Automatic Transmission Treatment Do?

Forte ATT restores the fluid properties that automatic transmissions rely on — viscosity stability, friction modifier chemistry, anti-wear protection and anti-foam properties.
  • ✓
    Smoother operation and gear changing Restores friction modifier chemistry for precise clutch pack engagement — eliminating harshness and jerkiness
  • ✓
    Reduces harsh take-up and flaring Controls the rate at which clutch packs engage for smooth progressive gear changes rather than sudden jolts
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    Maintains fluid efficiency over a wide temperature range Restored viscosity stability means consistent performance whether the transmission is cold or fully warm
  • ✓
    Prevents wear and extends transmission life Restores anti-wear additives that protect all moving transmission components
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    Prevents leaks by conditioning seals Conditions transmission seals — restoring flexibility and reducing minor leaks
  • ✓
    Remains in the system until the next fluid change All Forte tube products can stay in the system — no need to drain after use
Broad spectrum compatibility

Which Transmission Systems Is Forte ATT Compatible With?

One product covers virtually every automatic and hydraulic transmission type — from conventional automatics and DSG to Citroën LHM hydraulic systems and fluid suspension.

Forte ATT is one of the most universally compatible transmission treatments available — covering automatic gearboxes, DSG, Citroën LHM, manual gearboxes with crankcase oil fill, hydraulic jacks and fluid suspension systems.

For Citroën vehicles Forte ATT provides a specific additional benefit — it conditions the rubber seal between the hydraulic fluid pipe and gas globe, which is a common source of leaks and stiffness on older Citroën hydraulic systems. This makes it particularly valuable for Citroën owners experiencing heavy or stiff suspension alongside gearbox issues.

Broad spectrum compatibility — showing all transmission types compatible with Forte Automatic Transmission Treatment including conventional automatics, DSG, Citroën LHM hydraulic systems, manual gearboxes with crankcase oil fill and fluid suspension systems
🔄
All Automatic Gearboxes
All conventional automatic transmissions using ATF — any make or model
⚡
DSG Gearboxes
Direct Shift Gearbox — VW, Audi, Seat, Skoda DSG systems
🇫🇷
Citroën LHM Systems
Hydraulic systems using LHM fluid — conditions the rubber seal between hydraulic pipe and gas globe
⚙️
Manual Gearboxes (crankcase oil fill)
Manual gearboxes filled with engine/crankcase oil — overcomes notchy gear changes
🔧
Hydraulic Jacks & Rams
Hydraulic lifting equipment and rams using compatible fluid
🚗
Fluid Suspension Systems
Hydraulic fluid suspension systems — including Citroën Hydractive suspension
Instructions

How To Use Forte Automatic Transmission Treatment

Add to the transmission fluid. No draining required — Forte ATT works through the existing fluid from first use and stays in the system until the next fluid change.

Add Forte ATT via the transmission dipstick tube or filler point. It mixes through the existing transmission fluid immediately and begins working as the transmission reaches operating temperature. Improvement in gear change quality is typically progressive over the first few hundred miles.

  • ✓
    Add to the transmission fluid Via the dipstick tube or filler point — no draining, no specialist equipment
  • ✓
    Remains in the system No need to drain after use — stays active until the next transmission fluid change
  • ✓
    For Citroën LHM systems Add to the hydraulic fluid reservoir — same product, same process
  • →
    Monitor over the first few hundred miles Gear change improvement is progressive as the treatment circulates and the fluid properties are restored throughout the transmission
Prescriptive treatment protocol — showing how to add Forte Automatic Transmission Treatment to the transmission fluid via the dipstick tube with no draining required
Common questions

Every question about
Forte Automatic Transmission Treatment, answered.

My DSG gearbox jerks on low-speed gear changes — will this help?
Yes — DSG jerk at low speeds is a very common complaint and is often caused by degraded DSG fluid that has lost its friction modifier chemistry. The friction modifiers control exactly how the dual clutch packs engage at low speeds — when depleted the engagement becomes abrupt and jerky. Forte ATT restores this chemistry. Note that DSG gearboxes also benefit from regular fluid and filter changes which should be part of any maintenance approach.
My automatic gearbox slips — will Forte ATT fix it?
Forte ATT can help if the slipping is caused by depleted friction modifier chemistry in the transmission fluid — which is a common cause. If slipping is caused by physical wear of the clutch packs or mechanical failure within the transmission, professional diagnosis and potentially rebuild or replacement will be needed. Forte ATT is the logical first step before committing to expensive diagnosis — if it improves the slipping, the cause was fluid-related.
Can I still drive if my automatic transmission is slipping?
A slipping auto isn't safe to ignore — slipping generates heat that accelerates wear and can quickly turn a fluid problem into a mechanical one. If it's slipping badly, flaring between gears or dropping into limp mode, get it checked before driving far. If it's early and fluid-related, adding Forte ATT promptly can restore the friction chemistry before lasting damage is done.
How much does it cost to fix a slipping automatic transmission?
An automatic transmission rebuild or replacement is one of the most expensive repairs on a car — often well into four figures. If the slipping or harsh shifting is from degraded fluid and depleted additives rather than mechanical wear, a bottle of Forte ATT is a tiny fraction of that, which is why it's the logical first step before paying for diagnosis or a rebuild.
My Citroën's hydraulic suspension is stiff — will it help?
Yes. Forte ATT is specifically compatible with Citroën LHM hydraulic systems and conditions the rubber seal between the hydraulic fluid pipe and gas globe. Stiff or harsh Citroën hydraulic suspension is often caused by degraded LHM fluid and hardened seals — Forte ATT addresses both. Add to the hydraulic fluid reservoir.
How is Forte ATT different from just changing the transmission fluid?
Changing the transmission fluid removes depleted fluid and replaces it with fresh. Forte ATT supplements the existing fluid by restoring the additive package that has been depleted — it is not a replacement for a fluid change but a treatment that works between changes or as a first intervention when symptoms appear. If the fluid is very old and heavily degraded a fluid change followed by Forte ATT in the fresh fluid is the most thorough approach.
Can I use it on a CVT continuously variable transmission?
Forte ATT is formulated for conventional automatic transmissions and specific fluid types listed. CVT (continuously variable transmission) units use a specific CVT fluid with different friction requirements — using the wrong product in a CVT can damage the belt or chain. Check your vehicle's CVT fluid specification and contact us if unsure before adding any treatment to a CVT.
My automatic gearbox has never had the fluid changed — will this help?
Yes — Forte ATT is particularly useful for transmissions where the fluid has never been changed, as the additive package will be significantly depleted. However if the fluid is very old and dark, a transmission fluid change is also recommended. Forte ATT can be added to the fresh fluid after a change for the best possible result — restoring properties the change alone cannot add back.

Smooth the shifts.
Protect the
transmission.

Forte ATT smooths harsh gear changes and protects all automatic transmission types — compatible with conventional autos, DSG, Citroën LHM and more. No draining required. Free UK delivery.

£20free UK delivery
Order Forte ATT — £20 →
Use alongside
  • →
    Forte Diff & Gear Treatment If the vehicle also has a noisy differential or manual gearbox — Forte Diff & Gear Treatment handles EP gear oil applications alongside Forte ATT for automatic transmission fluid systems
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    Forte Power Steering Treatment For Citroën vehicles with both hydraulic suspension and power steering issues — Forte Power Steering Treatment also works with LHM fluid
Use alongside these products

Complete drivetrain care.

For manual gearbox or differential
Forte Diff & Gear Treatment
If the vehicle also has a noisy differential or manual gearbox alongside automatic transmission issues, Forte Diff & Gear Treatment is the correct product for EP gear oil applications — used alongside Forte ATT for complete drivetrain care.
View Forte Diff & Gear Treatment →
For Citroën LHM vehicles
Forte Power Steering Treatment
For Citroën vehicles use both Forte ATT and Forte Power Steering Treatment — both are compatible with LHM fluid and provide complementary benefits to the hydraulic system, suspension and power steering.
View Forte Power Steering Treatment →
At every oil change
Forte Advanced Formula Motor Flush
For complete vehicle maintenance — use Forte Advanced Formula Motor Flush at every engine oil change alongside Forte ATT for transmission care for the most thorough high mileage vehicle maintenance approach.
View Forte Advanced Formula Motor Flush →

Take A Look At Our 5 Star Reviews For Forte Seal Conditioner

At BMW Tool Rental, we pride ourselves on providing excellent customer service and offering honest and reliable advice to our customers. We understand that when it comes to your car, you want to ensure that you are using the right products and getting the right advice. That's why we take the time to listen to our customers, understand their concerns, and provide the best possible solution.

Our forte seal conditioner has received numerous 5-star reviews from our satisfied customers, who have found our product to be effective in reducing engine oil leaks and stopping blue smoke caused by worn valve seals. However, we don't just rely on product reviews to show our commitment to customer satisfaction. We offer a personal touch that sets us apart from other retailers.

If you have any questions about our products or services, we encourage you to reach out to us. We're always happy to help and provide you with the information you need to make the right decision. Whether you're looking to rent our AGA valve seal tool or purchase our forte seal conditioner, we're here to help.

Take A Look At Our 5 Star Reviews For Forte Seal Conditioner

At BMW Tool Rental, we pride ourselves on providing excellent customer service and offering honest and reliable advice to our customers. We understand that when it comes to your car, you want to ensure that you are using the right products and getting the right advice. That's why we take the time to listen to our customers, understand their concerns, and provide the best possible solution.

Our forte seal conditioner has received numerous 5-star reviews from our satisfied customers, who have found our product to be effective in reducing engine oil leaks and stopping blue smoke caused by worn valve seals. However, we don't just rely on product reviews to show our commitment to customer satisfaction. We offer a personal touch that sets us apart from other retailers.

If you have any questions about our products or services, we encourage you to reach out to us. We're always happy to help and provide you with the information you need to make the right decision. Whether you're looking to rent our AGA valve seal tool or purchase our forte seal conditioner, we're here to help.

Registered office
Clements Trading Ltd
82a James Carter Road
Mildenhall, Bury St Edmunds
Suffolk, IP28 7DE
Lichfield
BMW Tool Rental
63 Purcell Avenue
Lichfield
Staffordshire, WS13 7PH

Clements Trading Ltd trading as BMW Tool Rental. Registered in England & Wales, company no. 10629836. Registered office: 82a James Carter Road, Mildenhall, Bury St Edmunds, Suffolk, IP28 7DE.

BMW Tool Rental is an independent specialist supplying tool hire and Forte automotive additives. We are not affiliated with, authorised by, or endorsed by BMW AG. "BMW" is a trademark of BMW AG and is used here for descriptive/compatibility purposes only.

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