News flash! January 2010
Obsolete- New Process Gear manual transmission parts- for sale! Going through our inventory, we ...
Frequently Asked Questions (FAQs)
Q: What oil do you recommend for your Syracuse four-speeds? What about synthetics?
A: We recommend an SAE 90 petroleum oil (single or multiweight) meeting the American Petroleum Institute specification GL4 of – if it also meets the MT1 sub specification (this is the important part that assures compatibility with bronze synchronizer rings)—GL5. Name brand GL5s almost always meet the MT1 subspec, store brands never do. We like to see it written on the bottle to be sure, so we typically reach for Valvoline’s 80W90.
Regarding synthetics, some of these are lubricating miracles but two of their biggest features – super slipperyness and tenacity – have been known to bite our customers in the behind. Synchronizers are friction brakes and only function when the rings can cut the oil film. With some synthetics shifting becomes almost impossible and then, since draining and changing oil doesn’t strip the synthetic from the synchronizer cones, it is necessary to remove, disassemble and strip the gearbox. Finally, since specialty synthetic blenders have their eyes on axles rather than four-speeds, synthetics that worked yesterday may not work in the formulation on the shelf today. We advise customers who want to experiment with synthetics to buy two quarts—give one to your brother-in-law and, if it works for him, put the other in your car.
Q: I'm installing a SuperCase and the countershaft fir in the front case wall seems very tight. Is my new case defective?
A: Probably not. Customers are so accustomed to rebuilding worn out OE cases with enlarged countershaft bored that no one remembers how things were when cases were new. Tight is good. Use an arbor press if available and make sure to line up the flat on the countershaft rear before pressing or you'll need to do it again!
Q: I'm installing a SuperCase and my 'large pin' M20 cluster gear won't fit (or turn) in the case. Is my new case defective?
A: You probably have an OE cluster fitted with a backlash damper. Remove the damper assembly --- the cluster won't fir otherwise and your gearbox will perform equally well without it.
Q: My M20 Muncie has a spring-loaded plate riveted to the cluster; what's it for, and why is it only the wide-ratio?
A:
It's a 'backlash damper', a device designed to eliminate gear noise. As to how well it works, in an ideal environment --- new case. new gears, new damper assembly with fresh spring --- it apparently works well enough; in the real world forty years on probably not so much. In servicing the design's three common automotive gearbox appearances --- New Saginaw cluster gear (appeared 19966) technicians routinely discard the assembly without complaint. General Motors even delete it in some Saginaw production, although that may have been to save money in less noise sensitive applications (read 'cheap' H-bodies), not because it didn't work.
As to why the damper assembly is only found on one-inch countershaft M20's, the earlier 'small pin' M20's had the same 'head set' gear data as the M21 close ratio, changing the tooth counts by two to change the ratio --- 24/29 compared to 26/27. It follows, the laws of physics being what they are, that the M20's 24 tooth maindrive was weaker than the M21's 26 tooth. Whether this was a real problem or only a theoretical one is not clear, but GM decided to change to larger, strong and probably noisier teeth in the new 'large pin' M20, 21/25, and to counter the additional noise they fitted the damper.
Q: I see that some of your 26 spline maindrives are 'necked-down' behind the splines. Sure, that saves weight, but doesn't it make the shaft weaker?
A: It actually makes it stronger. The feature you're looking at is a torsion bar, just like the ones on old Mopar iron but less whippy and less likely to go bang in your garage at three in the morning. Here's the theory: shock loads, mostly from the clutch or poor shift technique, must be successfully handled for your gearbox to survive; concentrate them in time and space and the gearbox fails sooner rather than later. Spread them out, however, and the gearbox not only survives, 1t can handle more power. To do th1S we reduce or el1m1nate corners, maX1m1ze transition radii and allow the shaft to twist and untwist very slightly along a carefully shaped length.
Q: I'm buying a new gearbox (or rebuilding my current one) and I'll be buying a new clutch at the same time. Should I replace my 10 spl1ne setup with 26?
A: 26 spline inputs, properly designed, are significantly stronger than 10 spline. There are several reasons why this is so: (1) the GM 10 spline geometry is straight-sided with fillets of very small radius at the root concentrating bending stress in the corners, while the GM 26 spline geometry is involute ('gear-like' rather than 'key-like') with relatively large fillet radii and more than twice' as many driving surfaces; (2) involute splines are self-centering so the loads, smaller per spline already, are more evenly distributed; and (3) since the 'core diameter' -- the diameter of the circle tangent to the spline roots -- is larger for the the GM 26 spline than the GM 10 spline more torque can be safely transmitted down the shaft. All things considered, though, the difference is not so great that drivers of sensibly driven street cars should discard serviceable 10 spline hardware.
Q: Do all your 'M22-style' gearsets make the signature whine?
A: Yes. It's part of the experience, and we're smart enough not to tamper with it. That said, the actual distribution of frequencies depends on the tooth counts in the meshes generating them (for example. a 17 tooth gear turning at 3000 rpm produces 51,000 vibrations per minute. a frequency of 850 cycles per second -- well within hearing) so knowing the input rpm a sound analyzer can tell the difference between our several gearsets. If you have perfect pitch you might detect the difference, too.
Q: I understand that 'M22-style' gearsets are noisy. How noisy?
A: Everyone's perception of noise is different -- just ask your teenaged son. The question is further complicated by.the fact that most of our gearbox.customers are middle-aged males, a demograph1c w1th notor10usly less acute hear1ng than the1r W1ves, daughters and girlfriends. Assuming, then, that you can hear the difference between 'M20/21-style (high helix)' and 'M22-style (low helix)' gearsets, bear three things in mind:
- The 'M22 sound' in the movie 'Two Lane Blacktop' was added in post-production and doesn't necessarily reflect the sonic environment at the driver's seat.
- The loudness of the noise diminishes as you climb through the gears, low being louder than second, second than third, third than fourth: fourth, being direct, should make almost no noise at all, and that's where most of us live.
- Noise is a symptom of vibration which, in gears, is typically due to tooth-to-tooth spacing errors arising from cutting and heat treatment; as our gears are more accurate than forty-year-old original equipment the loudness is almost always less than that made by GM gears.
Q: I have some 'Muncie' gears in GM boxes that have a circled 'W' on them. What does that mean?
A: Gears with that marking are aftermarket gears produced by the New Bedford Gear Division of Borg Warner. For many years they produced the 'Muncie' service gears for General Motors.
Q: Who maintains your prints?
A: Clever question. If a vendor maintains the prints everything can be made to print -- he changes them to match production. Everything we buy is controlled by prints we draw and maintain. And we reject parts that aren't 'to print'.
Q: Parts can't be better than the prints from which they're made. Are your gears 'reverse engineered'?
A: In some cases, where OE prints aren't available, our gears are drawn from samples -- 'reverse engineered'. For us, this only establishes a baseline. We review the design, how the item functions and the parts with which it mates before releasing the item to our vendors. This enables us to make improvements, which we frequently do, and sets us apart in an industry where items are frequently purchased on price and with no regard for its environment.
Q: Does being predominantly an aftermarket supplier help or hinder your quality?
A: Back in the day the saying at one OE gearbox manufacturer was 'If it's to print it goes in service, if it's not it goes to production.' Most of our product is shipped loose to our customers -- there's no question that knowing this keeps us focused.
Q: Are your 'Muncie' four-speed gears as good as original equipment?
A: If they were only that good we'd reject them! Seriously, there have been so many improvements in manufacturing -- computer controlled machining, computer controlled furnaces for heat treat, statistical process control, cleaner steels -- that 'as good as 1970-era OE' is setting a fairly low bar. That said, some of our competition can't clear it, so the question is still valid.
Testimonials
Auto Gear Company has some great letters and photographs from satisfied customers- such as a police department race team, a bus line company, a landscape machine builder, a street sweeper manufacturer and some classic car enthusiasts. However, it takes time to get the requests and all the legal requirements done prior to publishing them on a website. So, until we get that done, our testimonial page is still under construction.