Disassembling and restoring the DeLorean manual transmission

My how car projects can snowball. It has been about four months since I started pulling the engine and transmission, and it has been a snowball of "while I'm in there" projects. In this post, I'll cover what projects I've tackled on the 5-speed manual transmission. When I pulled the motor, I pulled the motor with the transmission attached, and for me, this was the right choice, especially with how difficult it was to separate the two. 

I needed to separate them to be able to access and fix the leaking rear main seal, which I have yet to tackle. That's coming soon. I removed the M10 bolts that hold the engine and transmission together and was able to work them apart a little bit, but it didn't want to give up without a big fight. I had to pull and wiggle and pry for what felt like 30 minutes before the splines on the input shaft finally let go. After I had them separated, I could see the corrosion on the splines that were likely making it difficult. Here it was after I finally was successful in separating the engine and tranny:

The transmission was so nasty from years of leaks from just about every possible location. The horrible bell housing was likely from the rear main seal, the top of the transmission was possibly from top of the motor leaks or the previous slave cylinder that I replaced several years ago. Underneath was nasty from a combination of those leaks, plus the leaking lip seals around the drive axle flanges.

From the looks of everything, I believe I'm the first person to separate the tranny from the engine as the clutch and all of the components appear to be original.

Nasty, nasty, nasty:

When I replaced the slave cylinder all those years ago, one of the bolts holding it on snapped off when I tried to remove it. It has been on the car with just one bolt all of these years with no issue, but I thought it would be wise to try and fix it while I had such good access. More on that later.

I started to disassemble it, starting with taking off the slave cylinder:

I mounted it on an engine stand to make it easier to see the underside and assess my situation. More nastiness from the underside. This is the kind of grime that gets accumulated after years of leaks:

I removed the four bolts on the bottom of the bell housing when I went to separate the engine from the transmission and it had a steady leak formed. At this point, I knew I would at minimum be taking off the bell housing entirely to I could reseal the two surfaces. Here's how much gear oil leaked out in just a couple of days:

Here are the four bolts that I mistakenly removed:

I needed to drain the old gear oil before proceeding any further, and I also put the bottom bell housing bolts back in to temporarily stop any more leaks until I was ready to work on it some more.

I had to do something about the oil and grime caked all over the transmission, so I attacked it with a power washer to get the heaviest stuff off of it. That was a terrible job as the water would shoot back at me when spraying it into all of the fins on the sides and I was covered in oil and gunk by the end. It came out looking much better and I could work on it without making as big of a mess:

Looking at the back of the engine with the clutch and flywheel removed, it was clear that the rear main was a big culprit in the mess:

I decided that there would be no better time than now to make sure the transmission is fully functional with any obvious weaknesses addressed, and to make sure it is as reliable and leak-free as possible. To do that, I needed to take the transmission apart, so I started by taking pictures of how everything looked, including the various brackets, to make reassembly easier.

 

 

Unfortunately, one of the bolts on the mounting brackets snapped off while trying to remove it. I was going to get a lot of experience with drilling out broken bolts and tapping new threads:

 

 

I then removed the bell housing and was surprised at how much gunk and buildup there was inside all of the internal passageways.

With the bell housing removed, I could then start tackling the repair of one of the slave cylinder bolts that snapped when I replaced it, as well as the clutch master cylinder, in 2012. Like I said earlier, the slave cylinder worked just fine for nearly 10 years with just one bolt holding it on, but this would be a prime opportunity to fix this once and for all. 

I drilled out the old bolt using a dremel 562 tile cutting bit, which was highly recommended by my fellow DeLorean owners, and it was great. It basically just turns the old bolt to dust, but you have to be precise as you can sometimes get all of the old bolt material out without damaging the threads. I got as much material out as I was comfortable with and then decided to try and tap new threads.

I quickly discovered that this was a bad idea for this area as a crack started to form as I started to work in the tap. It was at this point that I realized that I would be better off with getting a new bell housing from DMCH.

The old clutch fork was so badly corroded that the back piece completely fell off when I tried removing the fork.

I also decided that I was going to make everything cosmetically sound too, including the brackets holding the transmission to the frame. Here's the before:

Here's after doing my best cleaning job with a wire wheel. It was about at this point that I decided that it would be worth my time and money to buy a sand blasting cabinet, which is what I did next. It has been several months since I bought it and it has been worth every penny. Below is also a pic of the before and after of the old clutch fork after going through the sand blast cabinet.

    

I was not going to try and reuse the old and broken clutch fork, which made it an excellent candidate to try out sand blasting. 

I then needed to remove the drive axle flanges as I prepared to disassemble the transmission. After driving out the retainer pins, the driver side slide right out, but the passenger side wouldn't budge. I actually had to resort to using a puller and heat to get the thing to move even just a little. I had to crank the puller down tight, heat up the flange, then beat it with a mallet, repeating this many, many times before it made any real progress.

There was so much corrosion on the splines that held the flange that made it so difficult to remove. I also discovered a lot of pitting on the flange outer surface where it met the lip seal, which meant that i would need to either sleeve the flange, or get replacement flanges. Costs were adding up fast.

Documenting the end cover before taking it all apart. I wanted to make sure my shift mechanisms all went back together the right way.

One of the things that you need to do in order to remove the 5th gear cover is remove the 5th gear detent ball and spring, held in place by an M12 plug that you're supposed to be able to remove with a flat head screwdriver. No matter what I did and how much force I applied, even with an impact screw driver, I could not get the plug to budge. Thanks again to the wonderful DeLorean owner community, someone recommended a specific tool for the job, which was KNIPEX alligator water pump pliers (8801250). My vice grips couldn't grip the plug well enough, but this tool had enough bite and was able to twist the plug loose immediately. It was awesome.

Documenting everything during more of the disassembly:

I was then able to take out all of the bolts holding the two transmission halves together and see the inside gears for the first time:

This is what the magnet looked like. It was covered in can only be described as a metallic oil blob. The stuff was fiercely difficult to remove from your skin when it came in contact with my hands.

I documented everything very thoroughly before I started pulling anything out of the case:

After removing the two shafts, I saw one of the main reasons I had decided to open the transmission: the retaining pin in the middle, known as a common failure point on this transmission. At first glance, it looked fine:

After I removed it with a punch, I could see that it had started to bend.

Here it is before I put in the new and reinforced pin:

Here's the inside of the other case:

I found that the factory must have used a sealant of some kind on some of the thru bolts. On one of the M10 bolts in the middle of the casing, I pulled out what looked like some kind of gasket maker or sealant. I made a note to do a good job in sealing the case when it came time for reassembly:

I took out the reverse sliding gear as I prepared to clean up the case:

Here it is before I started to clean it up some more:

Here is how it looked after spending a lot of time with degreaser and mini wire wheels getting into each of the fins and caverns. What a terrible job this was.

I decided to do the same thing for the other side of the transmission case and the 5th gear cover. More disassembly:

Here are many of the brackets and other pieces from the car that I sand blasted:

Here is the new retaining pin with the small reinforcement pin that goes inside of the new pin:

My attempt to document the placement of the differential adjusting nut before taking it apart more:

I couldn't get the casing as clean as I wanted with just wire wheel, so I decided to sand blast the exterior with something less abrasive. I chose crushed walnut shells and it helped get off the rest of the stuff that I thought would cause issues as I wanted to prime and paint the casing. Here's what it looked like after that and right before I put on the the primer and paint:

All painted. I even did a clear coat after this. Time will tell on how well it will hold up.

I also sand blasted and painted all of the brackets and miscellaneous stuff that was disassembled:

Here is my new bell housing from DMCH before I cleaned it up.

I waited to replace the lip seals on the transmission until after I painted the exterior so that I wouldn't have to worry about any over spray on the new lip seals. The old lip seals would not come out without a fight and I don't know how I would have successfully replaced them had I not had the transmission out of the car and disassembled. I ended up having to pound them out from the backside as pulling and prying them out without scratching the side of the transmission seemed all but impossible. 

I first attempted to pull and pry them out, but the lip seal just broke and I could only get the top piece out:

Here is the old lip seal finally coming out:

I went with the upgraded triple lipped lip seal from DeLoreanGo, but originally installed my first one backwards. I was thrown off because only installed backwards would the new seal be flush to the outside, which is what I thought it needed. I quickly realized that was incorrect and ended up destroying it when I punched it out and installed it the right way. I ordered a replacement and installed it the right way on both sides of the transmission.

On to the other side:

New and old lip seal comparison:

While the transmission was apart, I mistakenly pulled out the reverse shift rod too far, which is possible to do when the gears and shafts aren't in the transmission. I couldn't get it to push back in, and then realized that the detent ball and spring had fallen out and that I had bent the spring unknowingly when I was trying to push the shift rod back into place. I got replacement detent springs and made sure not to make that mistake again. Here's the bent and new detent springs:

Here's looking down the reverse light switch shaft where the detent ball is, before pushing it down all the way.

Here's are the two halves of the transmission sealed and back together with new bolts, washers, breather tube, lip seals, etc.:

Prepping to seal and install the new bell housing:

 

Installed. New bolts and washers all around:

New retainer pin w/ reinforced pin, similar to the retainer pin that I reinforced inside the transmission. Word of advice if you use this reinforced retainer pin here: install both of the pins together. I first attempted to install the larger pin first and the reinforced once second, but the resistance was too great and the reinforcement pin just bent. On the other side, I punched them in together and was successful.

My new bell housing didn't come with any locating down pins, so I had to get them out of the old bell housing to reuse them on the new bell housing. This was surprisingly more difficult than I anticipated because you can't just punch them out from the back side. There were three that I had to remove and reinstall from the old bell housing. Here you can also see the new clutch fork and throwout bearing. Behind the clutch fork is also a new dust seal. I also coated the clutch fork pivot ball with a 50/50 mixture of moly grease and anti-seize.

The transmission is back on an engine stand until I've got the engine ready for them to get reattached. Here are some more pics of how it turned out after almost all of the brackets and slave cylinder were put back on:

Here's a closer look at the breather tube that seems to be harder and harder to find. It's not necessary as it sits in the hole quite loosely, but I figured I might as well put one there. The original breather hose had virtually no material left and appeared to be plugged by the stuff inside the transmission. Having this breather cleared should also alleviate leaks, if any were caused by a plugged breather.