SunCoast Diesel ALTO 4L80/85E CATEGORY 4 REBUILD KIT - SC-4L80E-CAT4-A

Features and Benefits:

• NEW 4L80E OVERHAUL KIT
• ALTO RED EAGLE CLUTCH PACKS WITH INCREASED CLUTCH COUNT
• HIGH PERFORMANCE KOLENE STEELS
• UPGRADED INTERMEDIATE BAND
• NEW 4L80E FILTER
• NEW 4L80E BUSHING KIT
• NEW 4L80E THRUST WASHER KIT
• NEW LOW/REVERSE ROLLER CLUTCH
• UPGRADED 34 ELEMENT SPRAG
• UPGRADED STATOR SUPPORT BUSHING
• TORLON CHECK BALLS (10)
• UPGRADED CASE SUPPORT BUSHING
• TRANSGO STAGE 2 SHIFT CALIBRATION KIT
• SONNAX SMART TECH OVERUN KIT
• EXTREME DUTY FORWARD CLUTCH HUB
• UPGRADED BILLET OVERDRIVE PLANET
• 300M BILLET INPUT SHAFT
• AEROMET MAIN SHAFT
• TRIPLE DISC BILLET 258MM TORQUE CONVERTER

In this Category 4 4L80E Rebuild Kit, several upgrades are made when comparing it to the Category 3 4L80E Rebuild Kit. These upgrades include the forward clutch hub, which is upgraded to extreme 4140 billet steel, and the main shaft is upgraded to an Aeromet steel alloy. The overdrive planet is also upgraded to a billet piece in this kit.

The 4L80/85E Transmission

The 4L80E (and similar 4L85E) was a series of heavy-duty transmission assemblies from GM designed for rear wheel drive configurations. The 4L80E was heavily based on the TH400 first produced in October 1963, adding electronic controls and an overdriven fourth gear. The 4L80E's were optioned only in Chevrolet/GMC pickups, 2500 Suburbans, vans, and commercial vehicles, and the Hummer H1. The 4L80E proved to be a big hit in 1991 with its release in the Silverado 454SS.

The 4L80E (RPO MT1) is rated to handle engines with up to 440 ft lb while the big brother the 4L85E (RPO MN8) is rated to handle vehicles with up to 690 ft lb.

This is a complete 4L80E super rebuild kit containing Alto Red Eagle clutches with upgraded power clutch pack that includes additional clutches and steels. The additional friction count along with the upgraded steels will improve your 4L80E's torque and horsepower capacity.

This kit will include everything else you need to rebuild your 4L80E transmission. A new filter is included as well as a bushing kit and and thrust washer kit. The band in the kit is a high performance RedEagle band.

Supporting the stator

In this SunCoast GM 4L80E transmission rebuild kit we include an upgraded Sonnax stator support bushing.

GM 4L80E and 4L85E units may display no converter lockup or codes 68, 39, 1870 or P0741. Imbalance of torque converter clutch apply oil through the front stator support bushing contributes to this complaint. A journal clearance of .002" or more will generate sufficient leakage to cause lockup clutch slippage, causing the transmission to stay in third gear. Sonnax front stator support bushing 34016-W is designed to reduce leakage by minimizing journal clearance and also increasing journal length.

Sealing Things Up

SunCoast always upgrades the check balls in all of our new 4L80E and 4L85E transmission rebuilds. In this kit you will receive 10 of these new Torlon check balls.

These new checkballs (.250") are made out of tough, wear-resistant imidized plastic. The imidized plastic balls seal better than steel balls because they conform to the separator plate ball seats. Steel checkballs are hard and heavy, wearing separator plate ball seats from the repeated high impact of the ball on the seat. Elastomer or rubber check balls seal well. However, the elastomer material wears, reducing the size of the ball. Similar imidized plastic balls have been used on some original equipment late model valve bodies with excellent results. These imidized plastic checkballs are not available through the original manufacturer.

Upgraded sprag

The intermediate sprag on the 4L80E's typically come with a 16 element intermediate sprag assembly. The can lead to failure in high horsepower and torque situations. In this 4L80E transmission rebuild kit we are upgrading the sprag to a 34 element sprag doubling the torque capacity.

A Different Plate to Serve On

On many 4L80/85E rebuilds it is not uncommon to find the factory separator plate damaged beyond repair. This is a direct result of the factory steel check balls beating the plate repeatedly.

This SunCoast 4L80E rebuild kit also has a new upgraded separator plate included with it. We use a Transgo tempered steel separator plate for longer life. This plate is custom-plated for rust resistance.

Upgraded Case Bushing

If you rebuild a lot of 4L80E's then you already know that case bushing walkout and thrust washer wear are common issues in the GM 400, 4L80E and 4L85E units. This upgraded heavy duty case bushing kit combines the tried and true no-walk case bushing with a high quality thrust bearing that replaces the OE thrust washer and selective spacer to update this area for maximum durability in all applications. Selective shims are included for setting and adjusting rear end play.

When in Doubt, Ask for Help

Insufficient holding power in the overdrive roller clutch is the underlying cause of chronic overdrive roller clutch failure in hardworking 4L80E and 4L85E transmissions. When the roller clutch fails, the damage can be catastrophic, and the only fix is replacing the drum, planetary assembly and mating components.

The Sonnax Smart-Tech Overrun Clutch Valve Kit (34200-40K) offers a hydraulic solution to this known mechanical problem. With unique rerouting of hydraulic fluid pressure, this patented kit keeps the overrun clutch applied at all times (except OD 4th), reinforcing the roller clutch to adequately support heavy loads.

• Improves OD roller clutch holding power in D4 and Reverse ranges
• Extends the life of workhorse transmissions while preventing warranty claims and comebacks
• Installs quickly onto the valve body — no transmission removal needed

The Extreme Forward Clutch Hub

Sonnax Extreme Duty Forward Clutch Hub Kit (34322-02K) is manufactured from forged 4140 steel and features nitrited and case-hardened splines to eliminate spline wear in extreme applications. Includes bearing between hub and direct clutch housing. The case-hardening at bearing surfaces is removed to make further modifications easier. This forward clutch hub and bearing combination shifts the support of the forward clutch hub from the main shaft to the direct housing and sun gear shaft.

Compared to OE or other replacement forward clutch hubs, Sonnax Extreme Duty Forward Clutch Hub Kit (34322-02K) has an additional .025” thickness designed-in to reduce endplay and provide further endplay adjustment options. No machining is required for typical installation.

• Eliminates spline wear in extreme power and offroad applications
• Simple installation adds bearing and reduces unit endplay
• Easily modified for addition of second bearing

The Forward Clutch Hub

This 4L80E rebuild kit also comes with a new heavy duty forward clutch hub. This is an ideal upgrade over OE hubs in GM 400, 425, 4L80E and 4L85E applications that commonly see a high fracture rate of the forward clutch hub. It is made from 1045 steel forging and features a thicker cross section for increased strength and rigidity that is so commonly seen in these units.

• Made from forged 1045 steel
• Thicker cross section for increased strength
• Added durability for daily drivers, work trucks and mild performance applications

Upgrading the Input Shaft

The 4L80E, while inherently strong, still has limits. When we are talking about limits, we are faced with the realization that the factory cast input can and will break. This can be to either shock load causing a sheer break or due to torsional fatigue, causing a fatigue break.

In this SunCoast 4L80E Rebuild Kit, we upgrade the input shaft to a billet one. This new billet 4L80E input shaft is manufactured from 300M billet steel. This shaft is vastly stronger than the OEM shaft and is a must-have component for higher horsepower and heavy towing applications.

Upgrading the mainshaft