Interesting bearing failure artice on 6 speeds

Energy One


Troop Supporter
I too don't use 6th unless I'm cruising on the highway 70 or better. Yes, an outer bearing support would be wise if your running an open primary...:D


Active Member
I do not like the Baker six. I have heard all the comments about how great the six speeds are for a bike. I just don't see why. Its the one thing I don't like on my bike. I rarely use sixth gear. Unless, I am cruising 80 or beyond. To me it seems to lug with anything less than 80, and there is much more vibration. I live where the speed limit is 55mph, and do not get on a freeway often. With a bike that makes the horsepower ours do, I would think a 5 speed would work just fine. My bike has 3000mi on it and I have owned it for a couple months. I am looking for other options, but baker doesn't offer other gear ratios from what I have been able to find out.


Excellent article Neil. Like a few above I only use 6th when I'm above 75-80 mph and always downshift when accelerating.

I use Spectro 6 Speed Synthetic 75w-140w. Recommended by Baker..
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Active Member
Interesting article Nomad -- thanks for posting. Yep -- top gear for cruise only in any machine -- even a tractor =)
Whaaat? I stack hay in D 3!! :loony:
Anybody with tractor experience should know to drop it down to accelerate! :up:


Well-Known Member
my bearings just failed and I removed the trans wondering how to align it when I put it back in??? any help?? thanks


Same here, need instructions on alignment of transmission and belt. Removed my transmission to replace the bearings and now my belt wants to ride on the outer edge of both pulleys no matter how I adjust the rear wheel.


Well-Known Member
Same here, need instructions on alignment of transmission and belt. Removed my transmission to replace the bearings and now my belt wants to ride on the outer edge of both pulleys no matter how I adjust the rear wheel.

I didnt remove the motor so I bolted the inner primary to the motor then to the trans, tighten the motor up then the trans, then go underneath and tighten the trans
If you have not loosen your motor bolts at all?! After tightening the inner primary to your motor and transmission. Before tightening the 6 transmission mount bolts, you need to look that the gap the transmission may have bewteen the frame and transmission. It may need shimmed? From the sound of it and no matter what you do, belt keeps tracking to the outer edge after having the transmission removed and put back in, would mean when tightening your transmission down, your transmission is not align with your motor or rear wheel. Which also will cause other problems for you. Good luck!

Jersey Big Mike

Well-Known Member
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.
Valid points on torque and accelerating in 6th gear but your facts and math are off in other regards.

5th gear is 1to 1 ratio input of drive shaft to output shaft relative -- NOT related to rpm of engine
-- Think about it for a second -- How could you sell a 5thspeed tranny rated as 1:1 if your description were true since you are not taking into consideration the pulley ratio from engine to clutch in the primary, also the ratio from the output pulley on tranny to final belt pulley.

6th gear over drive input shaft if going .89 for every 1 turn of output shaft -- ie overdriving it. ie same speed on road, engine rpm goes DOWN in overdrive and therefore doesn't work as hard! (you have this described backwards.)


Active Member
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.

Not carved out of billet, or are our trannys made even cheaper for B.D.M. ?



Mr. Old Fart member #145
Staff member
Lifetime Supporting Member
What y'all beating' up on Neil for. This thread was started back in June of 2008.

Mr. Wright

Lifetime Supporting Member
Just replaced the outboard bearings on my 03, has close to 90,000 miles on it. To my knowledge, nothing has ever been done to this Jims, except through out bearing.


Active Member
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.

05 is the year I upgraded my Vintage to a six speed. Fortunately, my then Big Dog mechanic was going to a show where the Baker boys were showing off the new six speed tranny and were strongly advocating the new gearing that delivered a 1:1 in sixth gear. I chose that option and am really glad I did. That was 40,000 miles ago and she still sings.