One of the most sought after and coveted parts in the 3800 (and LS4) fwd aftermarket has been the GMR 1" Gear Set.  Anyone who wanted a fast car would have to find this needle in a hay stack, or be doomed to rebuilding the transmission more frequently, or just not even building the car in the first place.  MMS has stepped in to solve this problem.  Introducing the brand new MMS 1" Chain Gear Set for the 4t65e transmissions.  Our goal was to make the strongest and most reliable gear set possible, while keeping the price at a reasonable number.  Some people may say that spending almost $2k on a gear set isn't quite what they'd think of as reasonable, but considering used versions of the GMR have been selling for $3k and sometimes $4k, suddenly $1999.99 seems like a steal for a brand new set with a brand new chain.  Also with ours, you have the option of maintaining your transmission because we'll be selling the chain separately for those that ever want a replacement.  Keep in mind though, we will only be selling replacement chains to those who have actually purchased our gear set.  To ensure this, each and every sprocket we make has a set of numbers machined into it designating the number of teeth of the sprocket, relative side gear ratio, and even an individual serial number corresponding to the number of the actual set purchased.

When we began the design process, we took a look at what was currently out there:  stock gemini gear sets, 7/8" chain sets, and the rare GMR 1" sets.  None of these is perfect on their own.  Even the GMR has it's flaws.  We painstakingly went over all of the dimensions and characteristics of these various gear sets to come up with what we feel are the best dimensions and tolerances for the all new MMS 1" gear set.  We sought to achieve the strength of a GMR set with the reliability of a stock set, and this resulting design does just that.  We found that the 7/16" pitch GMR's although stronger on paper, had some major engagement issues, so we opted to go with a 3/8" pitch setup, just like the factory gemini and 7/8" sets have.  While it's not technically stronger than an ideally-functioning 7/16" pitch set, when you factor in the fact that the GMR we tested was binding when the chain would engage with the teeth on the sprockets, this represents a stress concentration which would drastically reduce the actual strength, thus making the 3/8 pitch a better choice.  The gears sets are made from pre-heat-treated chromemoly.  Blanks are CNC machined, the teeth are professionally hobbed, the splines are then cut to be a perfect snug fit on the input shaft and 4th clutch shaft respectively, then the sprockets are heat-treated to achieve the optimal hardness for the best strength and longevity results, and then the surfaces that need to be smooth on the sprockets are precision ground to the exact specifications of the factory parts so that everything installs and meshes properly into the transmission.  We also dialed in the thrust values to achieve the best out-of-the-box sprocket alignment possible.  We still recommend that transmission builders pre-load the case and checking these thrust numbers to accommodate for any case-shift between different castings of transmissions, but this is just to ensure you get every last bit of strength out of your new MMS gear set.

Lets talk gear ratios.  Our first batch consists of 3 options.

1) 35/35 teeth which is 1:1, combined with a typical 3.29 differential, this yields a 3.29 gear ratio

2) 33/37 teeth, which is 1.121:1, combined with a typical 3.29 gear ratio, this yields a 3.69 gear ratio

and a new ratio which you may not have been expecting...

3) 32/38 teeth, which is 1.188:1, combined with a typical 3.29 gear set, this yields a 3.91 gear ratio

Now many of you may be wondering why we didn't do 2.93.  We ran a prototype test batch of these sprockets to whittle down the design, dial in all the processes, and eventually send out to all the guinea pigs to install and test in each of their high performance fwd vehicles.  These customers gave us input of the gear ratios they were looking for, and we made our first batch options based off their input.  That being said the 3.91's were just an idea I was playing with that I wanted to experiment with, and am anxiously awaiting video from one of the guinea pigs.  So at this exact moment, it's true that we do not yet offer the 2.93 gears, but we've had enough interest from potential buyers and transmission builders that we will be adding this ratio as an option on our next batch.

We did some experimenting also with some coating options on the sprockets and on the chains, and as soon as we hear back from ours guinea pigs about how well these coatings are holding up, we'll be making the decision of whether to include this as an option.  The picture above with the black chain has a wear-resistant teflon-based coatings on the chain and on the sprocket.

We hope the 3800 and LS4 community is just as excited about this new product as we are to offer it to all of you.  Enjoy!

We've updated the item to have a fixed shipping value of $45.  This will be shipped via USPS Priority Mail unless maybe you're ordering other items at the same time.  This $45 value includes insurance for gear set in case of any damage during shipping.  This fixed shipping is also only available in the continental US only.  International shipping is available, contact mikem@milzymotorsports.com for shipping prices outside of the continental US.

P.S. - We'll be adding some better/touched up pictures here soon.  I just didn't want to delay the launch of this amazing product any further.