---
product_id: 321925241
title: "Stone River Products Castrol TranSynd 668 Allison 2021 Updated SPEC 1 GALLON ONLY BY DOXA WORLDWIDE"
brand: "castrol"
price: "€ 141.80"
currency: EUR
in_stock: true
reviews_count: 8
category: "Castrol"
url: https://www.desertcart.fi/products/321925241-stone-river-products-castrol-transynd-668-allison-2021-updated-spec
store_origin: FI
region: Finland
---

# Thermal & oxidative stability Superior gear protection Extended clutch & anti-shudder durability Stone River Products Castrol TranSynd 668 Allison 2021 Updated SPEC 1 GALLON ONLY BY DOXA WORLDWIDE

**Brand:** castrol
**Price:** € 141.80
**Availability:** ✅ In Stock

## Summary

> 🛠️ Drive with confidence, powered by Castrol TranSynd 668 – the ultimate transmission fluid upgrade!

## Quick Answers

- **What is this?** Stone River Products Castrol TranSynd 668 Allison 2021 Updated SPEC 1 GALLON ONLY BY DOXA WORLDWIDE by castrol
- **How much does it cost?** € 141.80 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.fi](https://www.desertcart.fi/products/321925241-stone-river-products-castrol-transynd-668-allison-2021-updated-spec)

## Best For

- castrol enthusiasts

## Why This Product

- Trusted castrol brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Heat? No Sweat!:** Exceptional thermal stability prevents oil breakdown even in extreme conditions 🔥
- • **Unmatched Gear Defense:** Protect your transmission with industry-leading gear wear resistance ⚙️
- • **Corrosion & Foam Fighter:** Keeps your transmission clean and efficient with excellent corrosion and foaming resistance
- • **Endurance Under Pressure:** Extended clutch-friction durability keeps your ride smooth and reliable 🛡️
- • **Universal Fit, Premium Performance:** Works seamlessly with Allison, GM 4L80, 6L90, and more—upgrade your fluid game today

## Overview

Castrol TranSynd 668 Allison 2021 Updated SPEC is a premium synthetic transmission fluid designed for heavy-duty trucks and GM transmissions. It offers superior gear protection, extended clutch and anti-shudder durability, and excellent thermal and oxidative stability to prevent deposits and oil thickening. Trusted by professionals, it delivers outstanding corrosion and foaming resistance and fits a wide range of applications, making it the go-to choice for enhanced transmission performance and longevity.

## Description

Buy Stone River Products Castrol TranSynd 668 Allison 2021 Updated SPEC 1 GALLON ONLY BY DOXA WORLDWIDE: Fuel Additives - desertcart.com ✓ FREE DELIVERY possible on eligible purchases

Review: Great Transmission Fluid - TranSynd 668 is one of the best transmission fluids available on the market currently. Developed specifically to meet rigorous Allison specifications for heavy-duty working trucks. Also works in GM transmissions like 4L80 and 6L90 and has better performance than standard ACDelco or GM Dexron VI or III fluids. OK to mix with Dex until the next fluid change. TranSynd is considered a more versatile premium synthetic option that meets a wider range of specifications and has a higher shear resistance. It can withstand more shearing forces without breaking down, making it a better choice for applications requiring extreme durability. Been running it in all of my GM and Allison transmissions for many years. Recommended.
Review: Great quality you can trust - This is the only transmission fluid I will use on my truck period !!

## Features

- Delivers improved gear protection.
- Delivers extended anti-shudder durability.
- Delivers extended clutch-friction durability.
- Excellent corrosion and foaming resistance.
- Excellent thermal and oxidative stability that helps to prevent deposits and oil thickening.
- Fit type: Universal

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B095SZB2DK |
| Best Sellers Rank | #5,132 in Automotive ( See Top 100 in Automotive ) #20 in Transmission Fluids |
| Brand | Castrol |
| Brand Name | Castrol |
| Container Type | Bottle |
| Customer Reviews | 4.9 out of 5 stars 947 Reviews |
| Item Form | Liquid |
| Item Weight | 3.41 Kilograms |
| Liquid Volume | 1 Gallons |
| Material | Synthetic |
| Package Information | Bottle |
| Recommended Uses For Product | Automotive |
| UPC | 079191219164 |
| Unit Count | 128.0 Fluid Ounces |

## Product Details

- **Brand:** Castrol
- **Item Weight:** 3.41 Kilograms
- **Liquid Volume:** 1 Gallons
- **Material:** Synthetic
- **Package Information:** Bottle

## Images

![Stone River Products Castrol TranSynd 668 Allison 2021 Updated SPEC 1 GALLON ONLY BY DOXA WORLDWIDE - Image 1](https://m.media-amazon.com/images/I/71RP2LrvVRL.jpg)

## Available Options

This product comes in different **Number Of Items** options.

## Questions & Answers

**Q: Can I use this in my 2001 silverado 2500hd with an allison transmission?**
A: Yes, I recommend flushing and filter (Both) try to remove as much of the Dino oil as possible.
Transcend works wonderfully in my '01 and '05 Chev Allisons

**Q: Can this be use with nissan rogue 2017?**
A: no

**Q: Ok for Genesis 80 2017**
A: no

**Q: I am trying to find the color of the fluid. Not able to find it on the product description. Any comments?**
A: It's red. Just like the older version.

## Customer Reviews

### ⭐⭐⭐⭐⭐ Great Transmission Fluid
*by B***L on January 20, 2025*

TranSynd 668 is one of the best transmission fluids available on the market currently. Developed specifically to meet rigorous Allison specifications for heavy-duty working trucks. Also works in GM transmissions like 4L80 and 6L90 and has better performance than standard ACDelco or GM Dexron VI or III fluids. OK to mix with Dex until the next fluid change. TranSynd is considered a more versatile premium synthetic option that meets a wider range of specifications and has a higher shear resistance. It can withstand more shearing forces without breaking down, making it a better choice for applications requiring extreme durability. Been running it in all of my GM and Allison transmissions for many years. Recommended.

### ⭐⭐⭐⭐⭐ Great quality you can trust
*by C***N on December 15, 2025*

This is the only transmission fluid I will use on my truck period !!

### ⭐⭐⭐⭐⭐ Great for the Allison
*by J***N on January 7, 2026*

Great fluid. Chevy shifting so much better now.

## Frequently Bought Together

- Stone River Products Castrol TranSynd 668 Allison 2021 Updated SPEC 1 GALLON ONLY BY DOXA WORLDWIDE
- Allison 29539579 Screw-on Filter with Magnet Filter Kit replacing filter for Allison transmission per OEM Specs, For utility terrain vehicles
- ACDelco GM Original Equipment PF2232 Engine Oil Filter

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**Shop now:** [https://www.desertcart.fi/products/321925241-stone-river-products-castrol-transynd-668-allison-2021-updated-spec](https://www.desertcart.fi/products/321925241-stone-river-products-castrol-transynd-668-allison-2021-updated-spec)

---

*Product available on Desertcart Finland*
*Store origin: FI*
*Last updated: 2026-02-28*