TRANSMISSION REBUILD VIDEO THREAD, Input sought! Options

[Dr Evil]

The video is getting closer to happening as Eric (cupomeat) and I just work on firming up a date in the near future. The video will cover the full tear down, inspection and rebuild of both side and tail shift (both /4 and /6) transmissions, but the video can not cover everything that I wish to. As such, I have taken the last 4 days in the middle of nowhere MN to start writing the notes that will accompany the video. The notes may be made available for free as well at a later time, but for now I need to make sure that they are as complete as I can make them. I have much of them done already, but I am still in the editing phase. If you have some info (factual or anecdotal) or experience with any of the topics, feel free to post them so I can either shoot them down or include them (IMG:style_emoticons/default/wink.gif)

Here is the outline so far:

Transmission rebuild video supplement:

Forward – What the deal is

Chapter 1 – Do I need a rebuild?

What external things to inspect

*Engine mounts
*Trans mounts
*Bushings
*Cone screws
*Clutch cable adjustment and issues
-How to adjust cable
-Broken tube

How to adjust the shifter

Inspecting core tranny

*Input shaft and output flanges turn?
*Input shaft play?
*“it shifts fine on the floor”, Oh goody, big deal.

A word on reading used transmission oil

Chapter 2 – Do I need that?

Myths and musings

*Billet intermediate plate
*Through bolting the intermediate plate/case/tail cone
*Lubricants
-Dino vs Royal Purple vs Swepco
*Galvanic chart: Stainless hardware FACTS
-SS hardware will not prematurely corrode your case and why not
*Corrosion protection
-Original factory coating
-Options for aftermarket

Chapter 3 – Tweaking your gears and diff

Gear selection

*Considerations
*Engine dependent gearing
*Interpreting gearing
*Intended usage of the gear box
*Flipping gears

Limited slip differentials

*The main idea - what they do
*Torque biasing
*Friction biasing

Welded differentials
*Don't do it!


Chapter 4 – Troubleshooting, care, and feeding of your 901

Problem list

*Reverse gear grinds
*Pops out of gear
*Grinds
*Whining
*Clutch will not disengage – resurfaced flywheel usage?
*Clunk and shifts funny
*Pivot ball leak?

General maintenance
*Oil changing

Appendix

Torques and values

*Case nuts, 8x1.25
*Speedo retainer bolt
*Throwout bearing guide tubs nuts, 10x?
*Detente package retainer bolt, 14mm
*Pinion bolt
*Input shaft nut

Special tools list

[underthetire]

Special tool list please.

[Dr Evil]

Good idea! Added to the first post. I will include graphics and pics as well.

[jmill]

How about a section on selecting gear ratios for your application?

NM saw it in you list (IMG:style_emoticons/default/biggrin.gif)

[rick 918-S]

Speciality tools as an option when purchasing a video or a source for same.

[ericread]

Where are the step-by-step instructions of tearing down and re-assembling the tranny?

The inspection and myth stuff is sure to be helpful, but what I need is a refresher from when I crack the case to when I bolt it back together.

Eric

[smontanaro]

... I need is a refresher from when I crack the case to when I bolt it back together.

"Assembly is the reverse of disassembly." What more do you need? (IMG:style_emoticons/default/biggrin.gif)

[Dr Evil]

Um, Eric, the video is intended to cover those things. I have no intention of spelling out how to rebuild a transmission. Ouch.

I added some other things in:
*Split TB LSD from FB LSD
*Added a bit on welded diffs

[Dr Evil]

I have the chapters 1 and 3 done for review. I will try to post them. I dont know how to post them in the .doc form for down load.

[FourBlades]

Maybe say a few words about converting tail shifters to side shifters?

How to refurbish your linkage to improve your shift action.

and the video needs hot chicks in it...

John

[Dr Evil]

Chapter 1 – “Do I even need a rebuild?”

What external things to inspect

It is usually a surprise to the bewildered owner of a poorly shifting transmission to find that the cause of the poor shifting is actually external to the gear box. The concept is fairly straight forward. The engine and transmission (drive-train) are solidly bolted together as as single unit, and they are suspended from the chassis with flexible rubber mounts. The shifter assembly is solidly connected to the body at the stick-shift (which is bolted to the floor in the cabin) and at the firewall bushing. This solid link to the body continues aft until it is connected to the transmission at the shift console. As such, any slop in the drive-train mounts, or the shift linkage, will cause the orientation between the drive-train and the chassis to change and subsequently the shift pattern location to shift making your shifting suck.
So, with that concept in mind, here is a list of things to check before blaming the transmission.

*Engine mounts – both side and tail shift 901 configurations in the 914 have rubber mounts incorporated into the engine mount bar. The side shift configuration has solid mounts from the bar ends to the chassis and rubber mounts between the engine and bar, the tail shift configuration is exactly the opposite. The two rubber mounts are intended to isolate drive-train vibrations from the chassis, but they can break causing the whole drive-train to shift. The common symptoms experienced when an engine mount fails are a “clunk” or “thump” when revving the motor or driving, and a shift pattern that continues to move around on you (gears are once in one place, then in another).

*How to test your engine mounts; side shift - Testing your engine mounts is pretty easy. First, realize that the side shift engine mounts are pressed between the engine and the engine bar. Thus, you need to lift the engine a little to see if the engine mounts are still in one piece. I have a method that I use and find to be pretty easy. First, jack the car up and place it securely on jack stands or ramps. Then, take a piece of wood and a jack and placing the wood under a solid part of the engine block on one side, and atop the jack, lightly jack under the engine to see if the engine easily lifts away from the engine bar. You are not trying to lift the car with the engine, you are only trying to see if the engine is still attached to the engine bar. Repeat this on the other side of the engine case. If the engine lifts a little from the bar, that is fine as the rubber mounts will yield a little bit. But, if the engine lifts very easy and any more than a little, consider changing your engine mount(s).

*How to inspect your engine mounts; tail shift - On the tail shift 901 in a 914 it is easy to check the engine mounts as they are located at the ends of the engine bar and are bolted to the frame. Inspection of these is pretty self explanatory and simply requires that one support the engine bar, pull the bolts, and inspect the rubber in the mounts. A good upgrade for these are the 911 engine mounts which tend to be cheaper than the 914 stock mounts, are solid rubber, and are overall better for enhanced stiffness and resistance to failure.

*Transmission mounts – transmission mount failure presents as a changing or sloppy shift pattern. The transmission mounts are straight forward and easy to inspect. Just support the transmission, remove the bolts from the mounts, remove the mounts and inspect.

*Shift bushings – shift bushings differ from side shift, tail shift and '70-72 914s that have been converted to side shift.

Side shifter:
Bushings are found in the firewall, in the joint just aft of the firewall in the shift linkage, at the side shift console where the rod passes through, and in the cup at the end of the shift rod. The majority of bushing issues are found when the firewall bushing deteriorates and disappears. Excessive looseness in any of the bushings will cause your shifting to suck.

Tail shifter:
The tail shifter has a cup bushing under the stick shift in the cabin, a firewall bushing (same location, different size than a side shifter), and one at the back end of the transmission where the rod mates up.

Converted '70-72 to side shifter:
For those wishing to convert their early 914 to a side shift, the only special thing to mention is that you must use a conversion bushing at the firewall. The firewall hole where the shift rod passes through in these earlier cars is larger than the one for the side shifting later model cars, and the hole in the middle of the bushing is smaller for the side shift rod verses the larger diameter tail shift rod. Thus, only the adapter bushing will work. Many times I have seen where one has used the standard side shift bushing in an earlier car only to have it be very sloppy in the firewall hole. The conversion bushing is readily available currently (01/22/10) and inexpensive.

*Cone Screws (side shifter only) – There are two cone screws to consider when your shifting gets crappy. One cone screw is located where the external shift rod joins the one sticking out of the fire wall. It is used to couple these two rods together and if it backs out the rods will have slop in them. The second cone screw is located at the aft most part of the external shift rod where it retains the shift cup. Again, if the screw backs out a little then play will be induced into the coupling and shifting will subsequently be affected. Cone screws come with a nylock deposit and should be replaced with new ones each time you remove them lest you suffer lost shifting. They are cheap, I am cheap, and I do it.

*Clutch cable – The clutch cable being too loose is probably one of the most common reasons that peoples shifting sucks. If your cable is too loose then you will not be able to fully disengage the pressure plate from the clutch disk/pressure plate and you will keep power to the transmission. If it is really loose then reverse will grind when shifting into it from a standstill. There is no way that this should happen if the clutch is fully disengaged. To properly adjust your clutch, you need to tighten the cable until the clutch disengages at about 1/4-1/3 pedal travel (see figure). If the clutch disengages too early then it is too tight, too late then it is too loose.

*Clutch tube – if your clutch cable seems impossible to adjust, you may be suffering from a separated clutch tube. The clutch tube runs through the center tunnel and is welded near the front to the drivers side of the tunnel and to the firewall where the clutch cable exits. Often, one of the welds brakes causing your tube to shift when you clutch in. This will cause your cable not to pull enough on your clutch and thus not fully disengage your clutch. Repairs for this issue are many and beyond the scope of this article. Search www.914World.com for information and advice on how to tackle this and other and other 914 related problems.

Inspecting a core transmission

So, you are considering buying a used transmission and the owner tells you that is shifted properly when before it was pulled and stored. So what? Unless someone can provide you with irrefutable evidence that the transmission was in good shape or has had some work done to it, it is a core. Feel free to violate this rule at your own financial peril. But, the box shift just fine by hand or in the car. I don't care. That and $3 will get you a beer at most bars, but it will not prove that your core transmission is any good. However, if it does not shift that doesn't mean anything either. More on that point later after rebuild. The output flanges should turn independently and together. If they do not turn independently, but do turn together, you may have a welded diff or a rare LSD. Not likely, but I don't want to dash your hopes (IMG:style_emoticons/default/wink.gif)
Definite signs of concern include, but are not limited to: drive shaft has much axial play, output shafts do not move at all, output shafts make a grinding noise when turning, current owner looks nervous and deflects your questions, etc.

A word on reading used transmission oil

A lot can be deduced from the oil you get out of a core transmission. However, you can not rely solely on this method as it is easy for someone to change out the oil and then let it sit leaving the oil relatively clean. Giant gold or other metal chunks are concerning for bearing failure. Gold flake in the oil is often indicative of normal wear and tear on the consumable parts in the stack. Oil that is gooey or burnt is indicative of a neglected box and may mean lots of parts to be needed to rebuild. Lots of shavings on the magnetic drain plug is not cause for concern as it is often due to normal wear and tear.

[Dr Evil]

Chapter 3 – Tweaking your gears and diff

Gear selection:

Considerations - What gears will work best for you depends on several factors: engine torque curve, HP, what the car will be used for. Ideally, you want to choose your gearing so that your engine RPM in every gear will be set up to extract the most use of the torque. For example, say you make peak torque between 4k-5k RPM. If you choose gearing that utilizes this band then you will get the best use out of your gear box.

Engine dependent gearing -The engine that is being hooked up to the gear box also determines how the gear box would best be setup. For instance, engines that make high torque at low RPMs, like V8s and large displacement Porsche 6 cylinder engines, require a taller set of gears than stock 4 cylinder engines which make their torque at higher RPMs (tall and small are slang terms that refer to how many RPM are needed to move the car. Small is 1st, tall would be 5th). As such, stock 1st gear in the 901 is useless and even dangerous to use with engines like V8s as it can cause damage if used. Stock 5th for the high revving /4 engine will also be too high for any engine that produces torque at low RPM and as such most people option to install taller gears in the 5th gear position.

Interpreting gearing - Porsche utilizes the alphabet to designate where gears lie on a continuum with “A” being the shortest stock gear, and “ZD” being the stock tallest

Stock gearing for 914/4 all years:
A, F, N, V, ZD

Stock gears for 914/6 all:
A, GA, O, V, ZA

*Note – the gearing for the /6 engine is a good example of how tweaks to what gears you have make better use of the torque provided by the engine, and how the shorter 5th (ZA vs ZD) provides for better cooling through higher RPMs.

Intended usage of the gear box - How you intend to use your gear box is another important factor to keep in mind when you are choosing gears. A very popular and readily available gear selection for courses with lots of turns, limited straightaways, and with a 4cyl with a normal torque curve is A, F, M, S, X. The first two gears are stock for the /4 while the 3, 4, 5, gears are all closer together than stock and are shorter overall. The MSX setup would absolutely suck on a course with long and plentiful straightaways, or on a freeway to and from a course. The stock gearing is fairly decent overall for a mixed race course. Other than these two popular configurations, the sky is the limit (or your wallet). I wish for you reading this to keep in mind that me telling you what you will enjoy best in terms of gears is like me trying on a pair of pants and telling you that you will like them based on my experience. As such, take the advise here in the gearing section as just that, and see what works best for you.

Flipping gears – Flipping gears is done for two major reasons: 1) To gain a ratio that is not available in the normal A-ZD offering. 2) To make a gear ratio that one wants without having to shell out the money for the actual gears (for instance, a flipped “M” gear is the same as a ZA which is stock 5th on a /6 box). Flipping an “H” gear and sticking it into 5th to gain a taller gear than ZD is a very popular application used in V8 configurations because they produce torque at lower RPM and cruising at 3.5K-4K RPM at freeway speeds with a ZD 5th gear is not very enjoyable in a V8.

Limited slip differentials (LSD):

The main idea – LSDs are great when used correctly. They are not cheap so getting one just to get one is something I would recommend against. To understand what an LSD does one should first understand what the standard differential does. The differential's primary job is to allow the wheel on the inner side of a turn to turn slower while the wheel on the outside of the turn turns faster. For example, a left turning car will have the rear left wheel turning slower and the right rear wheel turning faster. The problem seen with a stock differential occurs when one of the rear wheels slips. It is at this point that the stock differential will transfer all power to the slipping wheel while the gripping wheel gets no power. This seems retarded, but in normal everyday driving this is a perfectly fine design and not problematic. On the track, when rounding a corner and your wheel starts to slip you lose power to the drive wheel. This cost you time which is not acceptable in racing. It is this scenario that the LSD is designed to address. LSDs keep power to the wheel with the grip thus keeping the power to the road around a slide or corner. LSDs come in two flavor that are addressed below.

Torque biasing (TB) – The quintessential version know to most people of a TB LSD is the one manufactured by Quaiffe. TB LSD use a gear package inside the differential to divert power to the sticking wheel. These are my preference as they are readily available and require little if any maintenance when compared to the FB type of LSD. The only complaint that I have heard from a few people regarding the TB LSD is that around corners is can feel kind of ratchety. Some do not notice this at all.

Friction biasing (FB) – The stock LSD that came in some HB designated (case code on bottom rib starts with HB) 901 boxes was a FB type. A FB type is constructed much like a positronic differential in that it uses a wet clutch comprised of several friction disks and pressure plates. The thickness of the friction disks and pressure plates sets the percent of torque bias, typically 40 or 80% (percent diverted to drive wheel in a slip). These are smoother than the TB LSDs, but they have a serious problem in that they require constant replacement of the internal parts in order to work. Depending on who hard one pushes their car and how often, the FB LSD may need rebuilding once a season or more. The LSD has 4 friction disks, 6 pressure plates, and 2 wave plates/belleville washers in it. Each part can be purchased from vendors like Guard Transmission. The wave plates/belleville washers tend to be in fragments by the time you rebuild the LSD. As the LSD parts wear, the % of bias it provides decreases until it behaves just like a regular differential.

Welded differentials:

Don't do it! - I am still not sure why anyone would weld a differential. It is closer to an LSD than the stock differential, but when welded the differential no torque biasing in that the wheels always turn at the same rate. ALWAYS. This is freaking dangerous! Why? Picture that you are trying to turn, but you have a welded differential. Your car decides that it wishes to continue going straight (under-steer), nope, wait, now it wants to turn really fast (over-steer), nope, wait, now it wants to go straight again. Sounds like a recipe for disaster. I will not work on welded differentials because I don't trust them and don't want anyone's blood on my hands. Proceed along the welded differential path at your own peril.

[Dr Evil]

Maybe say a few words about converting tail shifters to side shifters?

How to refurbish your linkage to improve your shift action.

and the video needs hot chicks in it...

John

All will be covered in the video (IMG:style_emoticons/default/wink.gif)

[detoxcowboy]

Dr. Evil,
Maybe something on using used parts vs. new, You had mentioned to me that on some level used parts of a specific desighn would be better than a new replcement, and also led to the hint that replaceing certain parts with good used would be just as effective.. Maybe something along that line as looking at rebuilding yourself is daunting but adding up the potential new replacement cost is intimidaiting too.. Joe

[Dr Evil]

That will be in the video (IMG:style_emoticons/default/smile.gif)

[Gint]

Special tool list please.

Reasonable substitutes for special tools. (IMG:style_emoticons/default/idea.gif)

[detoxcowboy]

Dr. Evil

Anything about indexing the shift rod to the actual shifter, I have seen others have trouble this and myself included, it seems to be a trial and error, worst case unable to even reach gears or slide into postions, depth and angle play? The best article on this and the only one I could find was on Pelican and even then there was no set specific way just that there are adjustments to be adjusted..

[Dr Evil]

Crap, I totally forgot to add the shift adjustment. I have diagrams made (IMG:style_emoticons/default/smile.gif)

[ericread]

Um, Eric, the video is intended to cover those things. I have no intention of spelling out how to rebuild a transmission. Ouch.

I added some other things in:
*Split TB LSD from FB LSD
*Added a bit on welded diffs

Sorry Mike, I didn't read your thread carefully. This is in addition to the video... Makes sense now. Thanks!

Eric

[computers4kids]

I know your producing a DVD, but how about also cranking out a blue ray disk while your at it...not really any more work--you'll be able to include much more. Of course, the blue ray disk could be a premium purchase. Just think of all the cool interactivity that could be incorporated., humor cameos, diagram blowups, step by step lists, websites, interviews, etc, etc.