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B15/P11 tranny- why it's better than B13/B14

90K views 145 replies 65 participants last post by  Sigfod 
#1 · (Edited)
Well, I started pulling my B15 tranny apart today to install my friction type LSD and thought I'd share with all of you a little bit of what I found. We all know that B15 trannys hold up to high HP way better than B13/B14 trannys and I've frequently seen many folks wondering what exactly is responsible for this. Unfortunately, there really hasn't been any definitive answer. Thanks to a friend of mine who has many torn apart B13 trannys, I was able to compare and spot some big changes in the B15 tranny. Hopefully what I have found will shed some light on the major differences. I am assuming that the P11 tranny is identical but I don't have one to compare with here.

What we already know:
There is some seperation of the input and main shafts under WOT that occurs in B13/B14 trannys. This puts a great deal of stress on the ends of the gear teeth (at its worst in 3rd) leading to shearing in high HP scenarios. The B15 tranny does not seem to have this problem and thus holds up much better to high HP applications.

But why?:
Obviously the B15 case is significantly different than B13/B14 cases. An addition that was made with the introduction of the B15 tranny is pictured below.



The two seemingly pointless 14mm bolts pictured actually serve a very important purpose and that is reinforcement. Inside the sleeves that they screw into is a small spring that holds pressure on a check ball (2 springs and 2 check balls total). The check balls contact the two shifter rods that 'ride' the main shaft and essentially hold tension on them when in place. The shifter rods are notched where the check balls contact them and you cannot even remove the case without removing those two bolts first. This is quite a nice improvement over the B13/B14 design where the shifter rods are loose at best. In addition to this, the shifter rod that 'rides' the input shaft sports a much beefier fork and sits with much more stability over the B13/B14 counterpart. Support, stability and reinforcement are obviously greatly improved.

As far as the internals go, everything is different, including the diff. IMHO, it seems like the gear stacks are beefier on the B15 tranny (see pic below). Sorry that I have no comparison pics with a B13 or B14 tranny.



Probably the biggest difference that sets the B15 tranny apart though is the positioning of the reverse idler gear. To get to the gear, you must take off the small cover pictured below, and remove its retainer pin (also pictured below). This gear is actually held into the tranny case itself (by the retainer pin) and meshes with the input shaft. It basically forces the input shaft to stay completely meshed with the main shaft, yet another reason why there is virtually no play in these trannys.


Reverse idler gear cover


Removing the snap ring to take out the retainer pin.


Threading a small bolt from the cover into the retainer pin to lift it out.


The actual retainer pin removed.


After the pin is removed, the reverse idler gear pulls right out of the case.

So to highlight how the input and main shafts stay meshed in the B15 tranny, I give you the following synopsis:

Input shaft: Supported on one end by the input shaft bearing and on the other end by the reverse idler gear and a better design rear bearing, thereby preventing play under WOT.

Main shaft: Supported on one end by the diff final drive gear and on the other by the spring-loaded check balls as well as the bearing race, thereby preventing play under WOT.



Hope this sheds some light on some big differences between the two types of trannys......
 
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#5 ·
so does anyone know if the p11 tranny and b15 trannys are the same??? and do you have to do the same modifications to the b15 tranny as you do the p11 tranny thats explained in the techinical library?

edit: **** nevermind i just read that thread again and answered my own question... sorry that..

matt
 
#6 ·
Thank you coalitions-el, even I could understand your write-up and pics :tongue: . I fixed my B-13 tranny just last year, but next time that biatch starts acting up, it B-15 tranny here I come!
 
#9 ·
Shawn B said:
Thank you coalitions-el, even I could understand your write-up and pics :tongue: . I fixed my B-13 tranny just last year, but next time that biatch starts acting up, it B-15 tranny here I come!
No problem, even I was wondering why the B15 tranny was so much better than the B13/B14......until yesterday. ;) I figured I'd try to do a good write-up since I've seen so many other people who wondered as well.
 
#10 ·
Thanks for the writeup, bro. Very informative. :biggthump
If i ever blow up my P10, I'll know what to look for. ;)
 
#12 ·
coalitionSE-L said:
As far as the internals go, everything is different except for the diff. IMHO, it seems like the gear stacks are beefier on the B15 tranny (see pic below). Sorry that I have no comparison pics with a B13 or B14 tranny.
http://www.se-r-list.org/fifth.gear.phtml

just thought it would help a little bit.. although not by much..

 
#14 ·
SR20DEe said:
I have noticed before on other (simple case comparo's that the b15 tranny looks alot larger.. any way to take some measurements of the FINAL and gear set? also can you measure input to output shaft spacing? I'm simply curios :p
I won't be able to get back out and work on the tranny until this weekend, but I am definitely going to. I will most likely have it put back together too, but I can try to take some measurements for you while it's still apart. Can you be more specific as to what measurements you want taken? I understand that you want me to measure the final drive gear but what else specifically are you looking for?
 
#15 ·
with your caliper(or what ever measure ment tool) I want you to measure the Direct distance in MM from the centers of each shaft(input and output)
I'd Kill for the Sizes of the each of the input and output gears.. but it probably would be worthless :tongue:

ive bookmarked this thread For whenever I feel Competent enough to Tear down my Tranny (100,000 miles from now :D Or whenever i blow the 4th gear synchro away from abuse)
 
#19 ·
From looking at this pic:


and this one:


It looks like the gears are moved around on the shafts. Normally 5th gear is on top of the input shaft, but now it looks like its in the middle. In the B15 transmission, does the fork move between 2 gears, or one?
 
#22 ·
Its311Pete said:
Very nice write up Coalition. This is some insightful information.
Thanks. After the weekend I should have the measurements posted that SR20DEe requested (including the gear diameters).
 
#24 ·
Well, I did some digging and found out a few things.

1. What I initially called the "retainer gear" is actually the reverse idler gear. This came as a surprise to me because I've never seen a reverse gear that didn't have straight cut teeth. This gear also stays meshed with the input shaft at all times (as was noted in the original post for the added stability it provides) and is completely seperated from the striker area which is another weird thing. It does not move at all on its shaft (retainer pin) either. :confused:

2. The strange gear on the end of the main shaft that does not stay meshed with anything on the input shaft is actually the main reverse gear. It also does not have straight cut teeth......weird.

I'm still a little confused about exactly how this transmission engages reverse, but I'm not going to lose sleep over it. Anyhow, I've edited the original post with the "proper" terminology for this gear.

SR20DEe, I wanted to get out there and take measurements of the gears for you this weekend but I'm having difficulty with removing the shifter rods (I can't measure with them in the way). They have a unique lock ring in various places and I've tried about 5 different types of snap/lock ring pliers to remove them but haven't gotten my hands on a pair that will successfully remove these little bastards. I did see on Matco's website that they have exactly the type that I need......but I'm hesitant to pay $25.00 for a pair of pliers that I'm going to use once. Anyhow, I'll continue to search and that will be my last resort. When I do get the lock rings out, I'll take the measurements and post back here.
 
#25 ·
coalitionSE-L said:
I'm still a little confused about exactly how this transmission engages reverse, but I'm not going to lose sleep over it. Anyhow, I've edited the original post with the "proper" terminology for this gear.
Ok after staring at it for quite some time along with the FAST system, I see how reverse works. Reverse shares a slider with fifth and reverse. I have never seen a manual tranny with a synchro for reverse. Kind of cool. In the B13/B14 tranny when you shift into reverse all the sliders go neutral and the reverse idler is pushed up to engage the slider for 1st and 2nd which has mating straight cut teeth. So the B13/B14 tranny has a slider for 1st/2nd, 3rd/4th and 5th. This one instead adds to the '5th gear slider' making it a 5th/Reverse slider. Having a helical reverse is also odd as it will be as quiet as the other gears, i.e. no whirrrrrrrrrring when you back up as B13/B14.

The reverse idler gear gets pretty beat up on the side because of way it forces itself up to mesh the other two gears it contacts, so this is a improvement in 4 ways:

1. Reverse is quieter. (not a big thing but of note)
2. Reverse will be easier to shift into from a stop.
3. It braces the input shaft as noted before. :D
4. The idler gear will not wear like before.
 
#26 ·
Thomas Reynolds said:
The reverse idler gear gets pretty beat up on the side because of way it forces itself up to mesh the other two gears it contacts, so this is a improvement in 4 ways:

1. Reverse is quieter. (not a big thing but of note)
2. Reverse will be easier to shift into from a stop.
3. It braces the input shaft as noted before. :D
4. The idler gear will not wear like before.
Thanks for the additional info! I saw that the fork on the input shaft was for 3rd and 4th, the back fork on the main shaft was for 5th and reverse, and the front fork on the main shaft was for 1st and 2nd, but in looking at the two stacks, I couldn't figure out physically how the reverse system worked (e.g. B13 tranny has reverse brake cam to stop the spinning input shaft and allow the reverse idler gear to physically slide upward and engage the input and main shafts).
 
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