Swapping transmissions can often present unforeseen challenges, especially when working with unique vehicles like the Subaru SVX. One Subaru enthusiast encountered such an issue when attempting to install a Forester transmission into their 92 Svx, specifically noting a rear differential incompatibility related to axle insertion. This article delves into the potential causes and solutions for this problem, focusing on the 92 SVX and rear differential nuances.
The core issue reported is that the rear differential on the 92 SVX appears to be different from the Forester, particularly where the axles connect. This immediately raises questions about compatibility and the necessary steps to complete the transmission swap successfully. The 92 SVX is known for its distinct features, and the rear differential is no exception. Notably, the SVX is equipped with a rear Limited Slip Differential (LSD), which is a crucial factor to consider when troubleshooting compatibility issues.
One potential solution involves swapping the internal components, or “guts,” of the differentials. This approach aims to maintain the correct gear ratio required for the Forester transmission while ensuring axle compatibility with the 92 SVX. Here’s a breakdown of the components and considerations for this differential swap:
To achieve the desired compatibility, the goal is to combine parts from both differentials to create a functional unit. Specifically, you need to ensure:
- Correct Gear Ratio: The ring and pinion gear set from the Forester differential is essential to maintain the proper 4.44 gear ratio, which is designed to match the Forester transmission.
- Axle Compatibility: The central section, or “chunk,” of the differential from the SVX LSD is needed because it is designed to properly receive the 92 SVX axles.
When performing this swap, there are two main approaches to consider regarding which differential housing to utilize:
Option A: Forester Ring and Pinion into the SVX Housing
This method involves installing the Forester’s ring and pinion gear set into the original SVX differential housing. The pinion gear bolts to the housing, and the ring gear attaches to the SVX LSD chunk. If choosing this option, it is highly recommended to replace the pinion and side seals to prevent leaks and ensure proper lubrication. However, this approach may involve more complexity as it requires working directly with the pinion gear, which can be more intricate to handle and may affect the pinion seal preload.
Option B: SVX Guts into the Forester Housing
Alternatively, you can install the internal components from the SVX differential, including the LSD chunk, into the Forester differential housing, while retaining the Forester’s original ring and pinion gear set. This approach may be considered easier because it avoids disturbing the pinion gear assembly. In this case, you would transfer all side caps and shims from the SVX differential to the Forester housing to maintain proper clearances and bearing preload. New side seals would also be advisable in this scenario.
Choosing Option B might be preferable as it potentially simplifies the process and minimizes the risk of altering the pinion gear preload, which can be sensitive. Furthermore, the Forester differential housing may require a minor modification to accommodate the larger SVX LSD chunk. The non-LSD Forester housings often have small internal protrusions or “bumps” that may obstruct the SVX LSD unit. These bumps can be carefully ground down using a grinder to create sufficient clearance for the LSD to fit properly. This modification is generally straightforward and doesn’t require extensive work.
Another less certain possibility mentioned is exploring axle swaps or custom “Frankenstein” axles. This would involve finding axles that are compatible with both the Forester transmission and the 92 SVX differential or potentially fabricating a hybrid axle solution. However, this approach is less explored and may involve more complexity and uncertainty compared to the differential gut swap.
In conclusion, when encountering rear differential incompatibility issues while installing a Forester transmission in a 92 SVX, swapping the differential internals is a viable solution. Option B, installing the SVX differential guts into the modified Forester housing, appears to be a potentially easier and less risky method. While the exact procedure may require careful execution and potentially minor housing modifications, understanding these options provides a solid foundation for tackling this unique automotive challenge. Remember to always consult repair manuals and seek professional advice when undertaking complex modifications to your vehicle.
