Richmond Gear 79-0064-1 Pro Gear Ring and Pinion Set (4.88) for GM 8.875" 12-Bolt Differential
Product description
What this gear set is (and why people buy it)
Richmond Gear 79-0064-1 is a ring and pinion gear set built for GM 8.875" 12-bolt differentials. In plain terms, it’s the drivetrain “ratio swap” part that changes how your rear end pulls—typically something you’re shopping for when you want a different balance of acceleration vs. cruising. The set is specifically described for use with GM Impala models from 1965 to 1972, replacing OE aftermarket 988488.
On paper, the selling point here is the 4.88 gear ratio paired with precision-made components. That ratio is often chosen when you want the car to feel more responsive off the line, but it also means your highway RPM may not match the calm, relaxed feel you get with taller gearing. So, it’s a good fit if you’re chasing performance feel—but it can be a compromise if you mostly drive long distances.
The specs that actually matter for fit and strength
This isn’t a “universal” gear set. It’s aimed at a specific differential size and bolt pattern: GM 8.875" 12-bolt. It includes:
- 9310 stainless steel ring gear with 39 teeth
- An 8-tooth pinion
- A 1.625" pinion shaft diameter
- 30-spline pinion
- 12 ring gear bolts
The 4.88 ratio is tied to how those tooth counts and gear design work together. If you’re matching to an 8.875" 12-bolt housing, this is the kind of job where being “close” isn’t the same as being right. The set is described as designed to provide secure, robust installation thanks to the bolt setup and the pinion shaft / spline details.
Gear ratio details: what you can expect in drive feel
With a 4.88 ratio, the rear end is geared to multiply torque more aggressively. Practically, that tends to show up as stronger takeoff and better pull in situations where you want the car to respond rather than coast. The product description also points to performance and durability as the intent.
That said, it’s worth keeping expectations grounded: the right ratio depends heavily on your tire size, driving habits, and how you want the car to sound and feel at speed. If your priority is smooth highway cruising, a shorter 4.88 can feel busy. If your priority is performance and you’re building around that goal, it fits the brief.
Compatibility notes you should double-check before buying
The listing frames compatibility around GM 8.875" 12-bolt differentials and specifically GM Impala ‘65–’72. It also states that it replaces OE aftermarket 988488.
There’s also a condition mentioned about the differential carrier: the gear set is described as compatible with a 3.90 or higher ratio differential carrier. That’s an important constraint to verify against what’s already in your setup, because swapping gears into the wrong carrier condition can turn into a frustrating parts mismatch.
If you prioritize correctness, verify these items first: your rear end is truly an 8.875" 12-bolt, and your carrier ratio requirement matches what the kit calls out.
What stands out vs. more basic upgrades
Compared with simpler maintenance or “keep it stock” repairs, a ring and pinion change is a bigger commitment. You’re not just fixing wear—you’re changing how the car moves.
Where this set makes the most sense is when you’re already focused on performance tuning of the rear axle. The components are identified as stainless steel (9310) and the set includes detailed pinion shaft and spline information, which is exactly what you want when reliability matters and the job needs to hold up.
It may be overkill if your only goal is quiet, trouble-free commuting. Gear changes are for when you’re deliberately aiming for a different driving character.
Warranty and what it signals
The description says it’s backed by a 2-year or 100,000-mile warranty. That’s a meaningful safety net for something as labor-intensive as ring and pinion work—because you don’t want to find out later that the parts don’t hold up.
Still, warranty coverage doesn’t replace proper setup. Gear sets depend on correct installation practices and matching the right differential configuration.
What you get and who it’s for
In this package, you should expect a complete ring and pinion set built for the GM 8.875" 12-bolt differential. It’s aimed at people working on GM Impala ‘65–’72 or similar builds that require replacement of the OE aftermarket 988488.
It’s a solid match if you’re building a performance rear end and you’re specifically choosing a 4.88 gear ratio. It may not suit you if you’re trying to keep cruising RPM low or you don’t have the exact 8.875" 12-bolt application.
Final verdict
It’s worth buying Richmond Gear 79-0064-1 if you’re specifically targeting a GM 8.875" 12-bolt differential setup, you want a 4.88 ratio feel, and your Impala ‘65–’72 application (including the replacement fitment mention for 988488 and the 3.90+ carrier note) lines up.
Skip it if you’re not sure your rear end is the right size/bolt configuration, or if you’re primarily after a light-duty repair with no desire to change drivetrain character—because a ratio swap is a deliberate performance step, not a casual upgrade.