TheSamba.com :: View topic - Performance Transaxle / TDi Marriage from HELL

Sat May 30, 2020 8:41 am

.
.. thread title could also be “Syncro Trans Murder Mystery”

Background: This transaxle is built with ALL top tier goodies .. GT mainshaft and gears throughout, GT Billet carrier housing, new aluminum main case, new 5.43 R&P, etc etc ..

Installation is in a TDi powered Syncro Vanagon. The engine is modified to deliver greater hp/torque. The last transaxle failure in this Vanagon was a failed 4th gear. Although the original trans has not yet been torn down, the most likely failure is the synchro cone having been torn from the gear, due to shockload.

From Samba photo files:

Back to the customer's BRAND NEW transaxle.. After only a few months of service, the trans was returned to the original builder for severe shifting issues in 1st & 2nd gears. Upon disassembly, one of the two spring clips holding the 3 keys in the 1st/2nd operating sleeve assembly was found broken in half, with both 1st & 2nd gear brass synchro rings cracked in 3 spots (at each key slot, the smallest cross section of the ring).

I was called in for personal inspection, as the builder had never before seen a cracked synchro ring OR broken wire spring. I personally inspected all the components and finding no abnormal wear, we chalked it up to either driver abuse, towing a heavy load, or an overloaded Van. (The only other cracked synchronizer I had personally seen was from an overloaded vehicle.)

In speaking with the customer, the builder and I ascertained that none of the above criteria applied. The owner has had this van for many years, and is VERY familiar with these vehicles and how to treat them .. and while he has had many transaxle issues in the past, he purposely had this transaxle built with all the best components so as to never experience another failure.

The transaxle was reassembled with new operating sleeve assembly and new synchros for zero charge, and returned to the customer.

Fast forward just a few weeks .. The customer calls saying that balky shifting has begun in 2nd gear .. a precursor of the exact same problem developing again after a mere 1,000 miles. He's wise enough to stop driving the vehicle, and a week later personally delivered the transaxle for a second rebuilding.

At this point, the builder is in a bind, and as the parts supplier, I am equally stumped. The customer is naturally convinced that either the builder is incompetent, or the parts are defective. So, I decided to bring in a 3rd party to join me in disassembly, leaving the builder out of the autopsy process altogether.

What Tom Lengyel and I found was astounding and totally baffling.

First photo is for reader reference ..

New operating sleeve assembly:

The autopsy photos:

Broken key. The tiny broken off bit is what lodged beneath a synchro ring, sounding the alarm:

Cracks developing on all 3 keys:

The wire spring are being sawed in half by the vibrating keys:

Wire clip contacts backside of key at this wear point:

This photo shows normal interface between key and wire clip:

Brass synchro rings beaten by side-to-side vibration of keys:

As part of my inspection process, even though the problem clearly lies with engine vibration, I went ahead and measured my 1st & 2nd idler gears for concentricity. The gears checked out to be PERFECTLY concentric.

We also went ahead and inspected the 3rd/4th operating sleeve assembly and found that although FAR less pronounced, there was wear beginning to show on 3rd/4th wire clips as well.

Conclusion of autopsy: Vibration transmitted via the transaxle's input shaft is rattling 1st and 2nd idler gears so badly, that the Borg Warner synchronizing system is being torn apart. We obviously need to track down the source of this abnormal vibration.

The customer says he does NOT utilize a dual mass flywheel, which is often blamed for nasty TDi vibrations. To quote what he says ..

“I have a Pumpe Dusse TDI in my Syncro, It has big injectors, intercooler, S7 turbo and a tune from Kerma TDI. It has been in my van unchanged for about 70k miles or since 2014, I haven’t done anything to it in the last 3 years or so in regards to tuning or modification. This does not have anything special for a flywheel/adaptor plate, it is your standard inline 4 cylinder adapter plate and using a stock Vanagon clutch disc. It does have a stronger pressure plate but in the stock configuration.”

While I have LARGE bandaid transaxle design solutions for this odd predicament, I'm not sharing those solutions until the second chapter of this article, later this coming week. At this point, I'd MUCH rather get input from experienced TDi tuners in our Samba group, to hopefully shed insight on the customer's ROOT problem. Any ideas ?

Sat May 30, 2020 9:25 am

Thanks for posting a description of your troubleshooting process. It's interesting to read the progression from symptom to diagnosis to root cause to...? Looking forward to hearing more.

Sat May 30, 2020 9:25 am

I hate these transaxle threads, but at the same time appreciate them. They shake my confidence, but expand my knowledge.

Here is my TDI story. First, I'm running an 1.9 ALH. Measure HP and Torque at the wheels were about 100 HP and 150 Torque.

Originally I had a transaxle from an air cooled vanagon. 4.57 Ring gear from memory. It was connected with a stock diesel flywheel and clutch.

I ran this setup for a year without problems. The only downside was to cruise 70 mph the engine was pretty high in the revs.

At the time I reached out to Daryl at AA and had him build me a 091/1 with a taller ring and pinion along with a taller 4th gear. I'm recalling a 4.14 final and a .77 4th. Still using the stock diesel flywheel and clutch.

Fast forward 45000 miles later, transmission seems fine. I did notice I was able to make the clutch slip in 3rd. I decided to go with a TDI single mass flywheel and clutch. I had the bellhousing off to replace the input shaft with the TDI splines.

Impressions were, I think it felt slightly smoother. The disc springs are the size of conventional valve springs. Still seems to be shifting fine.

The only thing unususal that I noticed is a gear noise in 4th gear. It changes on and off load. I understand from Weddle, that they did have a run of gears that made a little noise.

So, this is of little help. Andy Bees another member is running a dual mass setup in his TDI powered van and pulled a trailer. He will probably chime in at some point.

Back in the day, I worked for the VW dealer network. It was common for the 1.6 diesel to start making a rattle noise sitting still in neutral with the engine running. Pressing in the clutch pedal the noise would stop. What we were finding was the disc springs were so worn, they were rattling in the disc. So between that and the TDI disc I have now, VW was trying to deal with the load on the clutch. Dual mass flywheels were also probably to work around engine harmonics.

I recall reading something before the internet. It was related to engine harmonics and 4 cylinder inline engines. 2.0 was about the limit of what you could run with just a harmonic balancer. Later larger engines started getting balance shafts to smooth them out.

I don't know what the answer is. I intended to install a TDI into my syncro, but it runs so well with the 2.1, that is on the back burner. That transaxle I built myself. If I sell the syncro, I intend to pull the 4 speed at some point in our TDI van and add a Peloquin and take a look further now that I have my own tools.

Sorry to see this. Small businesses can't take hits like this. There is not enough profit on the first one let alone a second and 3rd time.

I raced a VW scirocco for years. I would see some of the wear and failures above. One thing that helped was adding a shift limiter. Instead of using the hub as the shift stop, I added bearing locks to act as stops. In rushed shifts, you could actually flick the dogs out of the hub. Good luck sorting this out. Mark

Sat May 30, 2020 10:04 am

You said he has a 5.43 in a TDI? Seems a little high. What are his gears like?

For the record I have a DMF, 4.57 with 27" tires.

Would the driver resting his hand(with force) on the shifter while driving cause excessive force on the hub and associated wear on the keys?

Sat May 30, 2020 10:27 am

5.43 is lower than the standard 4.86. The overall gearing choice is matched to the VERY knowledgable customer's tire size. This is not a gear ratio issue.

The VERY experienced customer does NOT rest his hand on the shifter, and that wouldn't cause the damage shown anyhow.

To make it clear, I am only an expert on transaxle internal components, and claim zero knowledge on engine tune. I am looking for engine malfunction ideas to be relayed directly to the unfortunate owner of this TDi-powered Syncro Vanagon .. something like a sudden change in injector timing or whatever might introduce a NEW and destructive vibration.

Sat May 30, 2020 11:54 am

I wonder if the root cause to these trans failures is the engine being too secure in the chassis.

Sat May 30, 2020 2:40 pm

I have a Syncro alh tdi with a rebuilt AA transmission that included different 3rd and 4th gears to match my CLK rims and geolander tires. Details are sketchy.

I'm curious about the symptoms. I am getting close to dumping my swepco 210 as it is nearly impossible to shift into second or reverse when the motor starts without significantly warming up or rolling forward. Once warm it is butter smooth.

I rebuilt my shift linkage front to back as it was pretty knackered up. Shifts much better after the rebuild on the linkage but still impossible at startup when 70 degrees outside.

I’m hoping that switching to 202 will help this but am really just gambling.

What should a paranoid Syncro tdi owner be watching for?

Btw. I’m in portland and couple be a test subject.

Sat May 30, 2020 3:15 pm

I'm looking for input on TDi engine tune / malfunction (or any other ideas) that might be the source of extremely abnormal vibration, causing destruction of the Borg Warner synchronizer parts in VERY short order. This is not a slowly developing issue like synchronizers wearing out ..

Sat May 30, 2020 4:20 pm

In that case I would suggest you look at forums.tdiclub.com and ask the question there. I doubt there is a lot of knowledge here about a PD TDI. It does not seem to be a common engine to put into a vanagon.

Sat May 30, 2020 5:08 pm

MANY thanks for the tip, old_man ..

Sat May 30, 2020 5:12 pm

I have a beater Syncro that my wife uses as a work truck. It was abandoned by the previous owner, a car destroyer. It had a cracked 3/4 hub. Darryl fixed it for me. About two months later something bad happened. I took the box to Duvall again. One of the three dogs or keys in the 3/4 hub had broken in half. It broke near the middle. That was strange.

I have heard a lot of gearboxes that rattle at idle. Old BMW big sixes were bad about that. That noise always bothered me. People think of things like metal as solid, everything moves, bends. Everything has plasticity. It is a miracle that any machine works and holds up. Crankshafts twist, God only knows about the fire and pressure waves in the combustion chamber. Although BMW did build experimental combustion chambers that they monitored with high speed photography and radar.

I have an ALH Golf. I put a new Dual Mass Flywheel and clutch in it. If you don't understand why the engineers did something then you have a low probability of achieving a successful modification. I would not even think of using a solid flywheel on a diesel that came with a DMF. If a DMF is available that will fit in that bellhousing then it would lessen the observed damage. I cannot understand why people love to hate DMFs. Except for the fact that they cost money and are consumable components.

Paul concerning your question about the engine, I have a few suggestions. Did this engine come with balance shafts? Some people like to delete them. I have seen many diesel engines whose connecting rods became shorter for whatever reason, usually on individual cylinders. A compression variation would introduce extra harmonic dynamics. This could also originate with an injector problem. They can be bench tested. The Pump Deuse injectors are pressurized by the high pressure pump and by a camshaft via a rocker arm (two pumps). The mechanical cam setup is known to wear.

The newer diesels starting with the ALH in the US market are stratified charge engines. There are at least two injection events. The newer ones have more. The first charge is low on the stroke for a soft crackling burn to heat the air. "Tuners" are well known for making unwise decisions in fuel and timing maps.

The first thing i would check is the overrunning alternator decoupling pulley. It is there to diminish the shock and loads on the belt drive system. That belt exerts force on the crankshaft.

The most important suggestion I have is that you need someone with a newer Picoscope or equivalent to scope the crankshaft speed sensor directly. I would bet that this problem is being caused by rapid acceleration and deceleration of the input shaft. In other words the very thing that the Dual Mass Flywheel was designed to prevent.

Sat May 30, 2020 5:47 pm

Great info, hardway. I'm going to urge my customer to continue checking in on this thread directly (as well as visit the TDi Club forum), rather than me acting as middle man in an area that I know nothing about. I've done what I can to get a TDi tuning troubleshooting dialog started on his behalf.

I think the TDi guys in our Vanagon group will benefit from Tom & my autopsy report, and I'll be back in a few days to share my Big Bandaid solution(s) for powerful / potentially destructive engine conversions in our Vanagons ..

Sat May 30, 2020 6:02 pm

Out of curiosity do you know what 'stock clutch' he has and if he has the correct input shaft? I know there is some mixing and matching that can be done there. Not sure if it would cause the problems you found though, especially if it's been the same set up for 70k.

Sat May 30, 2020 7:29 pm

hardway wrote: ..I have an ALH Golf. I put a new Dual Mass Flywheel and clutch in it. If you don't understand why the engineers did something then you have a low probability of achieving a successful modification. I would not even think of using a solid flywheel on a diesel that came with a DMF. If a DMF is available that will fit in that bellhousing then it would lessen the observed damage. I cannot understand why people love to hate DMFs. Except for the fact that they cost money and are consumable components...

I also have an ALH Golf & an ALH Jetta. I put a dual mass flywheel in my jetta when I converted it from an Auto to a manual. The transverse mounted engine is allowed to move following the rotational plane of the crankshaft.
These engines move & shake a lot (esp when cold). The exhaust has a flexpipe installed because of this.

I think a forum member here with a TDI swap needed to completely remove one of the mounts to get rid of excessive cabin vibration noises.

When installed in a Vanagon, the engine is much more rigidly mounted.

Take a look at these videos. See how the engine is allowed to move?

Sat May 30, 2020 7:50 pm

I think there's something wrong with both those engines, which is causing them to shake at idle like that. Both my '96 Passat TDI and the donor '01 Jetta TDI for my Vanagon swap were silky smooth idlers.

Sat May 30, 2020 7:53 pm

Zeitgeist 13 wrote: I think there's something wrong with both those engines, which is causing them to shake at idle like that. Both my '96 Passat TDI and the donor '01 Jetta TDI for my Vanagon swap were silky smooth idlers.

For sure. I'm just pointing out that the design (and more importantly, location) of the engine & trans mounts allows the engine to shake like that. See how every pipe, hose, etc has some type flexible section built in? Nothing is rigid.

I think if I had a TDI in my van, I would confirm how much the engine can move (in that same direction)

Sat May 30, 2020 10:03 pm

gears wrote: The customer says he does NOT utilize a dual mass flywheel, which is often blamed for nasty TDi vibrations.

When operating correctly, the dual mass flywheel softens engine pulses. It has a much higher failure rate than single mass flywheels and once it has failed can cause a lot of mayhem. When operating correctly, the DMF should transmit less vibration to the trans.

hardway wrote: The newer diesels starting with the ALH in the US market are stratified charge engines. There are at least two injection events.

Actually, the dual stage injection started with the AAZ and was unchanged through the ALH. I have avoided becoming familiar with the PD engines although I imagine they are more than dual stage injection.

gears wrote: I'm looking for input on TDi engine tune / malfunction (or any other ideas) that might be the source of extremely abnormal vibration, causing destruction of the Borg Warner synchronizer parts in VERY short order. This is not a slowly developing issue like synchronizers wearing out ..

There are several things that come to mind that could cause excessive vibration to be transmitted to the transaxle. Injectors could certainly cause that. The nozzles are wear items and an imbalance between the set can cause significant vibration. As I mentioned I have largely avoided becoming familiar with the PD fueling but have still read plenty about them. My understanding is that the camshafts have a tendency to wear. The camshaft is what drives the PD injectors. A worn camshaft seems a likely culprit. Worn or improperly functioning lifters could also be a contributing factor. A compression check might show an imbalance between cylinders. EGR tends to clog the intake with soot/oil/carbon. A clogged intake could be causing an imbalance of air to the individual cylinders.

Sat May 30, 2020 10:42 pm

That engine setup puts out around 400Nms of torque. That is the double of the vanagon gearboxes were designed for. 2.6 SA vans had 200 Nm but the gearbox had modifications like the oiling plates.

Aidan Talbot the reputable UK gearbox specialist says DMF is a must with tdi, flooring under 2000RPM is a big no-no, and he suggest oil change in every 2 years.

By factory setup the pd runs smoother than VE tdi but the Kerma tune with big injectors surely alters that. I dont know how the Kerma tune was built, but usually tunw on the VW TDI means adding more fuel duration and more advance start of injection. Both adds to the rattle.

Sun May 31, 2020 5:37 am

You guys are offering extremely valuable input that I really appreciate .. and I hope the customer appreciates.

My role is to provide components that are vastly superior to OE .. but this particular issue is quite obviously WAY beyond component strength / quality, and admittedly way beyond my scope of knowledge / experience.

Sun May 31, 2020 6:12 am

I'm having a EA288 TDi installed in my Westfalia 2WD, so I'm very interested in this topic. Would you please put a link to the thread you started in the TDIClub forum?