--- title: What Transmission Output Shaft Spline Count Do I Need for a Gearstar Transmission and Transfer Case? description: Find Gearstar transmission output shaft spline counts for 700R4, 4L60E, 4L65E, 4L80E, and 4R70W applications, plus Dana 20 adapter details. --- [Skip to content](https://knowledgebase.blueprintengines.com/knowledge/what-transmission-output-shaft-spline-count-do-i-need-for-a-gearstar-transmission-and-transfer-case#main-content) English Show submenu for translations ![IN CRATE ENGINES..png\]](https://knowledgebase.blueprintengines.com/hs-fs/hubfs/IN%20CRATE%20ENGINES..png?height=40&name=IN%20CRATE%20ENGINES..png) Open main navigation Close main navigation - English Show submenu for translations - Go to www.blueprintengines.com Go to www.blueprintengines.com How can we help you? - There are no suggestions because the search field is empty. 1. [Knowledge Base](https://knowledgebase.blueprintengines.com/knowledge?hsLang=en) 2. [Technical Support](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en) 3. [Transmissions](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en#transmissions) # What Transmission Output Shaft Spline Count Do I Need for a Gearstar Transmission and Transfer Case? ## Selecting the correct driveshaft yoke, transfer case, or adapter requires knowing your transmission's output shaft spline count. This is especially important on 4x4 applications, where transfer case input spline counts and adapter compatibility must be verified before assembly. This guide applies to customers using Gearstar Builder Series transmission packages with BluePrint Engines and swap applications. ### ***What Are the Output Shaft Spline Counts for Gearstar Builder Series Transmissions?*** Use the following spline counts when determining yoke, driveshaft, transfer case, or adapter compatibility. | Transmission Configuration | Output Shaft Spline Count | | --- | --- | | Chevrolet 700R4 | **27-spline** | | Chevrolet 4L60E | **27-spline** | | Chevrolet 4L65E | **27-spline** | | Chevrolet 4L80E | **32-spline** | | Ford 4R70W (2WD) | **28-spline** | | Ford 4R70W (4x4 with Bronco Dana 20 adapter installed) | **6-spline** | ### ***What Information Do I Need for a 4x4 Transmission Swap?*** Before ordering a transfer case, adapter, or related driveline components, verify: - The exact transmission model. - The transmission output shaft spline count. - The transfer case make and model. - The transfer case input gear spline count. - Whether an adapter is required between the transmission and transfer case. Failure to verify these details can result in incompatible components and installation delays. Does the Ford 4R70W Use the Same Yoke as an AOD? **No.** A 4R70W transmission requires a yoke specifically designed for the 4R70W. The AOD yoke should not be substituted because the barrel diameter differs by approximately **0.100 inch**. A commonly referenced heavy-duty yoke for the 4R70W is: - **Sonnax Part Number: T3-3-14061HP** Always confirm fitment with your driveline supplier before ordering. What Transfer Cases Work with the Gearstar 4R70W Dana 20 Adapter? The Gearstar 4R70W adapter package uses a **6-spline output configuration** when the adapter is installed. ### Important Compatibility Note The Dana 20 adapter is designed specifically for: - **Ford Bronco Dana 20 transfer cases** It is **not intended for other transfer case models** without additional modifications or alternative adapters. ### ***Why Is Transfer Case Input Spline Count Important?*** The transfer case input gear spline count must match the transmission output or adapter configuration. A mismatch can cause: - Inability to assemble components. - Transfer case installation issues. - Premature drivetrain wear. - Additional adapter requirements. - Delays during engine and transmission swaps. Always verify spline counts before purchasing mating components. Frequently Asked Questions ### Can I use a 27-spline transfer case with a 32-spline 4L80E? **No.** The spline counts must match or an appropriate adapter/conversion solution must be used. ### Is every 4R70W transmission 28-spline? **No.** A standard 2WD 4R70W is **28-spline**, but a 4R70W equipped with Gearstar's Bronco Dana 20 adapter uses a **6-spline output configuration** at the adapter interface. ### Can I use an AOD yoke on a 4R70W? **No.** The AOD yoke differs in barrel diameter and should not be used in place of a dedicated 4R70W yoke. ### What should I verify before ordering a transfer case adapter? Verify: - Transmission model - Transmission output spline count - Transfer case model - Transfer case input spline count - Adapter requirements ### Why won't my transfer case fit my transmission? The most common causes are: - Incorrect spline count - Wrong transfer case input gear - Incorrect adapter - Misidentified transmission model - [General Support](https://knowledgebase.blueprintengines.com/knowledge/general-support?hsLang=en) - [Technical Support](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en#main-content) - [General Engine FAQ](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en#general-engine-faq) - [BluePrint GM Style Engines](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en#blueprint-gm-style-engines) - [BluePrint Ford Style Engines](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en#blueprint-ford-style-engines) - [Transmissions](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en#transmissions) - [Fuel Systems](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en#fuel-systems) - [Parts and Accessories](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en#parts-and-accessories) - [Carburetors](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en#carburetors) - [Alternator](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en#alternator) - [Term X](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en#term-x) - [Valve Train](https://knowledgebase.blueprintengines.com/knowledge/technical-support?hsLang=en#valve-train) - [Factory Five FAQ](https://knowledgebase.blueprintengines.com/knowledge/factory-five-faq?hsLang=en) - [Engine Specs](https://knowledgebase.blueprintengines.com/knowledge/engine-specs?hsLang=en) - [Discontinued Engine Specs](https://knowledgebase.blueprintengines.com/knowledge/discontinued-engine-specs?hsLang=en#main-content) - [Engine Support](https://knowledgebase.blueprintengines.com/knowledge/discontinued-engine-specs?hsLang=en#engine-support) [![Chill listening crop-3](https://knowledgebase.blueprintengines.com/hs-fs/hubfs/IN%20CRATE%20ENGINES..png?width=92&height=24&name=IN%20CRATE%20ENGINES..png "Chill listening crop-3")](http://navy-blueprint-logo) www.blueprintengines.com Help Center Copyright © 2026, BluePrint Engines