Interesting bearing failure artice on 6 speeds

Nomad2day

Longhair Redneck Geek
While searching the Internet to learn what makes the baker 6 speed, how it is made and researching bearing failures, I ran across this article. Thought I would throw it out here to hear other people thoughts on this.

Dr. Chaos Service Bulletin #26 speed transmission bearing failure.
There has have been numerous reports on trap door bearings and the main shaft main ball bearing going bad prematurely on six speed transmissions on all makes. I have personally seen bearing damage and main shaft bending from the Rev Tech 6 speeds. I've also heard from very reliable sources that Baker and yes even Harley has have had trouble with their six speed transmission bearings. The next sentence is not entirely accurate but will suffice for this discussion. The six speed transmission uses pretty much the same design as the proven 5 speed design only with an extra gear. The problem is, is with the main shaft and the fact that the clutch pack is mounted so far away from the shaft support which is the main shaft ball bearing. The main shaft and the clutch pack is unsupported at the end. The clutch pack hangs off the end of the shaft and is flexed back and forth by the torque of the engine. The tightness of the primary chain and the secondary drive belt also contribute to stress on the main shaft bearing, which then this transfers the force to the trap door bearings. This unsupported main shaft design was adequate with a 50 or 60 hp engine putting out low torque numbers. With the recent trend in high HP and high torque engines and ever increasing and cheap affordable cubic inch upgrades, like for the Twin Cam (95 cu in.). T the 5 -speed transmission is meeting its design limits. Remember the stock 5 speed transmission in 5th gear is a 1 to 1 ratio, which turns the rear wheel one revolution for every full revolution of the engine. Now enter the 6 speed transmission with a final drive ratio in 6th gear of .83 to .89 (overdrive). Which means the rear wheel turns only .83 to .89 (roughly) of a revolution while the engine turns one complete revolution. This means that there is a lot more torque being transmitted to the unsupported main shaft with the same clutch basket hanging off of the unsupported end of the shaft. What this does is stress out the main shaft bearings and the trap door bearings prematurely before their time causing transmission failure or at the very least an early rebuild. I have seen 6 speed transmissions from every major manufacturer needing bearing overhaul around the 20,000 to 30,000 mile range. Which is way too early! I think there is something we can do to slow down this process considerably. I think we are riding these 6 speeds all wrong (me included). I think we are accelerating far too often in 6th gear and not down shifting to 5th gear as we should. We do this because we can. We now have so much more torque with these more powerful engines that we can accelerate in 6th gear without downshifting. I believe This is the problem. If we do all our accelerating in 5th gear, then once we reach cruising speed, then and only then shift into 6th for cruising. That way no excess torque is placed on the unsupported main shaft and our aftermarket transmissions will and should last longer. Just my two cents.
 

Fibersnake

Banjo Playing PsychoBilly
Very interesting indeed and makes allot of sense. I like the note of the shifting to 5th for aceleration and just keeping it in 6th for crusing. Not sure how other use the 6th gear, but myself I tend to not put in in 6th until 75 MPH or more, like to keep my RPM up near the 3000 Range and if I do drop the hammer, normally shift it down then come on up till I hit 3500 or so.

So far no issue with the tranny and hopefully will have none. Not sure if the info you posted is accurate or not, but will say that I ride mine more like he suggest and (knock on wood) no issues with the tranny yet. Oh I do use just the standard RevTech Tranny fluid and change it out about ever other oil change. My not be crap, but it is habbit and oil is cheap.
 

Raywood

The Pirate
Staff member
Lifetime Supporting Member
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Troop Supporter
I would add that this may not apply to the 05 and newer bikes which use the DSSC. This primary allows for a shorter shaft than the HD style primaries that have to space the motor out to clear the fatter tires such as the one on my 03.
I haven't had an issue with either of my BD's and they both had a lot of miles on them. And 95% of these miles have been hwy miles. I use 6th gear all the time but I'm usually running 85+ unless I'm with Knotso then it's closer to a 100!
I've also only changed the oil in my 05 three times now after the 500 mile service and it has over 52,000 miles on it. I'm pretty easy on my bike other than running at high speeds on the fwy. Also, the only oil I've used is the Redline Heavy Shockproof!! Great stuff!!!
Interesting article though. I remember when HD did the recall on all the 6 spds when they first come out.

:flag:
 
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BigDogBro1

Made in the USA
Raywood's 52k miles of experiance makes sense to me - Both us BigDogBros don't hammer our bikes and now I'm glad of it. I for one have always considered 6th gear as a cruise overdrive and don't lug it down. Plus, treating your dog like it's a Suzuki Haybusa is something you may end up paying for eventually. Personally I don't hammer my bike when I ride - because I like to ride it, not fix it.
 

T Mack

SUCKER FREE
Raywood's 52k miles of experiance makes sense to me - Both us BigDogBros don't hammer our bikes and now I'm glad of it. I for one have always considered 6th gear as a cruise overdrive and don't lug it down. Plus, treating your dog like it's a Suzuki Haybusa is something you may end up paying for eventually. Personally I don't hammer my bike when I ride - because I like to ride it, not fix it.
It sure is hard not to with all the power we have.... But I'm with you, I try not to Dog my Dog too much...:D :D :D
 

Vegas

Well-Known Member
Sul....6th is definitely not as deep as it used to be on the dogs. My 03 Chopper had a tallker 6th and so did my buddies 06 APC with the baker. Overdrive was never meant for accelerating in any machine. What is the first thing you car does when you give it some throttle...kick down a gear. I always drop it in 5th to accelerate unless I am going 75 or 80.
 

chacha

Chaff Your EHC!!
Calendar Participant
Interesting article Nomad -- thanks for posting. Yep -- top gear for cruise only in any machine -- even a tractor =)
 

reloaderbmg

OLD DOG
only dog mine now & them! and in low gears, 6th is at 60mph.
at no time from 4th gear up im below 2,000rpm. and higher in 6gear!
 

EJ

Member
I agree 6th gear is 65 or better I dont like to lug the motor in 6th if i slow down or accelerate I downshift to 5th. I like to give the ol girl a bit of hell every now and then just to show them harley boys i ride with what the old dogs got.:cheers:
 

Raywood

The Pirate
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Lifetime Supporting Member
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Troop Supporter
BD 6th gear is 1 to 1.

Bakers is .86? to 1
Baker introduced the DD6 (Direct Drive 6 spd) and BDM adapted it with the introduction of the 05 models.
Earlier models used the OD6!

Baker still offers both tranny's.

:flag:
 

V

Guru
Good info
If you were to switch to a open primary it seems like you would want the outer support, right?
 

awags

Member
According to the 04 manual 65 is the absolute slowest you should use 6th. I wont even think about it till atleast 75! I never gave the tranny a second thought but lugging the engine is terrible for it- Let her scream- They like the higher rpm's anyways. I just got back from tha S&S 50th, put on about 400 miles and averaged 43-44 mpg, the best tank @ 46mpg with the girlfriend and a loaded saddle bag! I wasn't riding it hard- but do always keep up the rpm's.
 

Fibersnake

Banjo Playing PsychoBilly
awags,

On the 05 they list 62MPH@2000RPM for 6th and 81MPH@3000RPM for 6th. I normaly do not even think about 6th unless seeing 75 plus for a good long distance. My bike does seem to like to see the 3000 RPM light on or just a tad below activation.
 

emcclary

Active Member
I agree with most 6th gear is strictly a 70+ mph event with downshifts as needed due to traffic etc.
 

woodbutcher

Mr. Old Fart member #145
Staff member
Lifetime Supporting Member
i hear ya.

just saying that we dont have that true overdrive that the article was referring to.

Baker does offer a high TQ bearing. wonder if that would help with any shaft flex?
seems to me that if you have the opportunity/need to rebuild the tranny, if at all possible, change your bearings to needle instead of ball bearings to get rid of the point loading and give more of a contact area for the support of the shaft. thought may be off base, but i don't think so.

damn, it's good to be back!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 

scubaman15

Well-Known Member
Lugging the motor is never a good idea... But I will say this if it breaks I don't want it, I ride my bike and I flog it when its safe to , Its a rush and makes me feel alive ,I also corner it till something drags ...shit I bought this bike for the performance and every Harley rider who thinks thay got a hot bike wants to try it "and some of them have true hot rods" but I love the power of the 117...when the Warranty runs out I will test the tranny with even more power ... If you can't run it through the gears what good is it!! IMHO
 

Nomad2day

Longhair Redneck Geek
As Raywood said, The artice may not really apply to our transmissions due to the being a dssc. This is from the Baker site explaining the DSSC some and how it is different from the other transmission. I am talking about the clutch being wat out on the mainshaft anyway.
Good stuff.

BAKER Drivetrain | Custom Transmission Products

the D.S.S.C.™ drivetrain assemly (Drop Starter Slam Clutch)

DSSC is a complete drivetrain unit consisting of a Right Side Drive transmission and an enclosed primary drive. The inner primary, outer primary, tranny case, trap door, top cover, and pulley shroud are all carved out of 6061-T6 billet. We cut no corners to make this premium drivetrain look like Tiffany jewelry and take punishment from a big inch motor.

the art of balance: low and centered

In 2001 we introduced Right Side Drive (RSD) for ground-up, wide tire customs. Any primary drive setup could be used in conjunction with RSD, but there was a problem. Actually not a problem but more like an opportunity. Using a left side drive primary in conjunction with RSD left a gaping hole between the inside of the primary and the left side of the transmission case - the space once occupied by the left side drive pulley. Our new DSSC primary slams the clutch inward 2.3-inch into the space once occupied by the pulley - thus the phrase SLAM CLUTCH.

While we were slamming the clutch inward, we rotated the starter down into the vacant space behind the transmission case - thus the phrase DROP STARTER. Lowering the starter in the chassis permitted seat heights to be lowered up to 2.5-inch. It also cleaned up the left side view profile.

DSSC is a complete drivetrain unit consisting of a Right Side Drive transmission and an enclosed primary drive. The inner primary, outer primary, tranny case, trap door, top cover, and pulley shroud are all carved out of 6061-T6 billet. We cut no corners to make this premium drivetrain look like Tiffany jewelry and take punishment from a big inch motor.

DSSC is a complete RSD drivetrain system and is compatible, without modification, with Daytec, Rolling Thunder, Dakota Thunder, and similar RSD Softail and Hardtail frames with zero engine offset and a left tranny offset. The offset is built into the inner primary - no spacer required. DSSC is set up for 240/250 tire applications using a 1-inch belt. 280 and 300 tire applications are possible with a 530 O-ring and an offset sprocket, call for details.

DSSC Features:

RSD6 6-speed gearset with 2.3-inch shorter mainshaft
43 tooth sprocket-basket with 9 friction plates
28 tooth motor sprocket - no compensator
88 pitch 428-2 double row chain
O.E. type chain adjustment and shoe
Stock-like 1.54 ratio primary reduction
Doweled top cover for positive location
Compatible with Spyke starters (not included)
66 tooth ring gear for big motors
No jackshaft on the starting system
Hydraulic clutch actuator has a 1.5-inch piston
Mechanical clutch actuator compatible with stock cables
With or without neutral switch
 

Throttle

Member
My 5th gear is only effective above 60 mph. It just seems to get louder and louder. I changed the transmission fuild to Spectro 75/140. The transmission was very quite for the first 2,500 miles, but it is getting loud again. I have 14,500 miles - 2007 Bulldog2007. Unfortunately, i do like to jack rabbit occasionally up to 60.
 
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