Integra & Honda B-Series Transmission Gearing

Integra LS transmissions are the cheap and plentiful option for Honda B-Series drivetrains. Their long gearing usually means less shifts on the race track, but could we go faster with different gearing? Well, that will depend on the track, and the situations you find yourself in during a race…

A Quick Primer

Your transmission multiplies engine torque to give you far more torque to turn the wheels. It’s based on your gear ratios: if your 1st gear ratio is 3.230 and your final drive is 4.266, then your effective gear ratio is 13.779. That means that 100 ft-lbs at the crank becomes a whopping 1377.9 ft-lbs at the wheels (minus drivetrain losses), but it will also take 13.779 rotations of the engine to make 1 rotation of the wheels.

Think of it as trading RPM in exchange for more torque to accelerate the car. This is also why we generally want to shift at the maximum RPM in each gear when racing, even if the engine’s powerband isn’t up that high… the lower gear is giving us more actual torque at the wheels than if we were to shift earlier into the next gear.

Some Actual Data

We’ll compare 4 different transmission options:

1) Cheap & Plentiful: Integra LS (’94-’01 RS/LS/GS; ’90-’93 is same but shorter 5th: 0.742)
2) Performance Oriented: Integra GS-R (’94-’01)
3) The Exotic: Integra Type-R (’97-’01)
4) Hybrid: LS w/ 4.71 final drive and GS-R 5th gear

Wow, the Type-R gearing looks awesome! What’s the catch? Let’s take a look at the trade-offs, for an engine that revs to 7000 RPM, and runs 205/50-15 tires:

So, ignoring the cost and difficulty of finding a Type-R gearbox, its advantages still aren’t free… The awesome torque multiplication becomes short-lived when it has less usable range in each gear, resulting in needing to shift into higher gears sooner, needing to use 5th gear at all of our tracks, and more shifting in general. It’s worth pointing out that the GS-R and Type-R engines rev much higher than this 7000 RPM example, so that’s a big part of the formula for those drivetrains.

The Type-R gearbox is certainly no slouch and could still be great for this example car, but you’ll have to work for it, and may find yourself more often needing to use a non-optimal gear to avoid shifting in a corner. Take another look at options 2 (GS-R) and 4 (Hybrid LS), which also offer increased performance, but with a bit more range in the gears and hopefully less cost too.

Here’s another way to look at it, showing the effective torque multiplication at each speed (MPH):

Decisions

As you can see, they each have their strengths over the others at different speeds, with even the long LS gearing being helpful for staying in lower gears for longer, and the mighty Type-R gearbox becomes a problem at 100+ mph when it shifts to 5th. Everything has its trade-offs, but what we’re aiming to do here is to optimize the gearing for the conditions that we’re racing under. Not just basic acceleration that’s easy to show in graphs, but also trying to optimize acceleration while coming out of a corner, without running out of gear and needing to shift in the middle of it.

We’re looking for the compromise that best fits most tracks and situations, and remembering that it is advantageous to have more torque multiplication / acceleration earlier rather than later, but having to shift more often or sooner can be a disadvantage too. The stock LS gearing isn’t “bad”, and I’ve previously won races and set lap records with it, but I do believe it could be a little better. A high-revving engine can also help make shorter gearing more practical and enable you to use lower gears for longer, but a difficulty of that approach is getting a good wide powerband (and horsepower numbers can rise rapidly above 5252 RPM, so our engine rules effectively limit this advantage too).

5th gear is a bit of a special case, because it’s often so long that you can’t use all of its range, and you feel a big decline in acceleration if you ever need to use it on track. But, it doesn’t have to be a fun-ruiner like that… A dedicated race car will usually want to shorten it so that your maximum RPM in 5th is just a little higher than the top speed you’d ever be able to reach on track. When fuel economy and highway cruising don’t matter, there’s not much sense in running a 5th long enough to reach ~140 – 160 MPH if the car is only capable of 130 and you can only get it up to 110 by the end of the longest straightaway. Once you have a good performing 5th, it can make even more sense to shorten your other gears (or final drive) so that you can make use of all 5 gears instead of just the first 4.

Some other variations to consider:

1) GS-R transmission with a Type-R 5th. This is nearly identical to the effective ratios of gears 3 – 5 from the Hybrid LS setup described here, plus you’ll also have more LSD options (including using a stock Type-R LSD). Unless your car is a cable clutch, or you already bought an LSD for the LS fitment (like I did), this will likely be more cost-effective than buying a new final drive for an LS.

2) Hybrid LS w/ 4.71 FD and a Type-R 5th (instead of GS-R 5th). This would yield a 119.9 MPH top speed (instead of 129), and an effective gear ratio of 3.994. A slight edge whenever you need to use 5th.

Note: As of this writing (2018), Front4 rules limit each car to just one gearing change per season. We don’t want people changing their gearing for every event in an attempt to optimize it for each track, because that would drive up everyone’s cost to be competitive. Instead, find a good compromise that fits the majority of the tracks and run that all season.

Honda B-Series Transmission Tinkering & Tips

  • If you have a gear grind (3rd is most common), you should replace the synchros AND the selector sleeve. The sleeve teeth often get chewed up worse than the synchros. There are plenty of guides and videos on the Internet on how to do this, but it’s not too bad, and you shouldn’t need a press to get to the 3-4 or 5-R synchros and sleeves (everything on the mainshaft should slide off). Synchrotech sells carbon synchro upgrades and hardened sleeves.
  • It’s fairly straightforward to swap gears 3, 4, or 5 with most other 1992 and newer B-Series transmissions (for the same gear number). You can often find them from Synchrotech or on eBay. You will likely need/want a press for the countershaft’s top bearings, and then everything else can slide off the shaft with a little encouragement. Each “gear” will actually be a pair of two gears, one on the mainshaft and one on the countershaft. Keep the pairs together; don’t try to mix & match within them, as the engagement will be wrong and may cause damage. There may also be some synchro differences in some cases, and I’m not sure if that impacts cross-compatibility of the gear itself.
  • It’s not much more work to swap out the final drive or the differential. The final drive is the huge ring gear with the differential bolted to it, and it’s paired with the countershaft itself. Don’t forget that the bolts on the differential are reverse thread!
  • The Integra Type-R came stock with an LSD, which will bolt up to a GS-R final drive, but not to the LS or B16A2.
  • The LS 4.266 final drive and differential uses a different ring gear bolt pattern than the GS-R/Type-R 4.40, so if you want to swap between these, then you’d need to do both parts. The LS and GS-R/Type-R differentials also use different bearings to match the tranny case, so that would need to be dealt with too. My suggestion is to keep it simple and just go aftermarket for whatever transmission you have.
  • There are aftermarket final drives available for the LS fitment, but they aren’t always advertised as such. Check with the manufacturer before buying anything; the MFactory 4.71 final drive I put in my ’95 LS transmission was listed on their website as being for the B16A2, but some of their resellers listed that same part number as fitting the ’92+ LS. I got it and it bolted right up.
  • Swapping 1st or 2nd gear is not practical, because their mainshaft gears appear to be permanently attached.
  • It will take more work to swap a Hydro transmission (like from a ’94-’01 Integra) into a car that was designed for a Cable transmission (’90-’93 Integras and most Hondas of that era), or vice versa. The difference is primarily in how the clutch is actuated (via hydraulic fluid or using a cable), but there can be some speed sensor and transmission mounting differences too.
  • The pre-1992 transmissions have some fitment and internal differences that may not be compatible with the ‘92+ models.
  • Not much is known about the compatibility of parts from the ’98-’01 CRV’s manual gearbox, but if you’re adventurous, that may be a fun project. The manual option appears to have only been offered on 4wd models, so you probably wont be able to bolt up the whole transmission, but I wouldn’t be surprised if the gears inside of it are compatible with other B-Series transmissions. Here are the ratios:
    • 1st: 3.500
    • 2nd: 1.956
    • 3rd: 1.344
    • 4th: 1.071
    • 5th: 0.812
    • Final: 4.562

 

Weston

Front4 Series Co-Director #73 White 1995 Acura Integra

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