syncro TDI = trans death?

[tencentlife]

hp = (Tq[ft.lb.] x rpm)/5252

Engine 1 makes 150hp @ 3200 rpm, so (150 x 5252)/3200 = 246 ft.lb.

Engine 2 makes 150hp @ 4800 rpm, so (150 x 5252)/4800 = 164 ft.lb.

A geartrain isn't exposed to hp, it transfers torque. Torque determines geartooth face pressure and bearing loads.

Rpms determine surface speeds on gear faces and in bearings, and lubrication quality by secondary effects. Surface speeds and bearing loads at lesser pressures become marginal factors with sufficient lubrication. Gearface pressure is a lot harder to mitigate with lubrication.

To evaluate a geartrain's capacity as a function of hp is not a useful basis for comparison. Look at the torque, that's the primary factor, it swamps all others.
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[caravelle c]

Double post

[caravelle c]

A friend of mine here in Germany is rebuilding 2wd-, auto- and syncro transmissions.
He said that just TDI powered Vanagons are destroying the gearboxes that much.
It's all about torque, especially the torque peaks!

In a TDI it's common you have torque peaks of 500-600Nm in a split second. Even when the data sheet reads: 300Nm at 1500-3500 rev/min.

[zuhandenheit]

I run an AAZ and am wondering, with some of you, about the extent to which these TDI concerns apply to the IDI.

I have a Giles performance pump, intercooler, and run 15-18 psi. I wouldn't be surprised if the power output is higher than a stock TDI. However I have less low-rpm torque than a TDI with equivalent HP.

Should we expect an IDI to put equivalent stress on transmissions, relative to power?

[?Waldo?]

If you produce the same power at the same rpm, then the torque output is the same and in that case I would expect the trans to see the same abuse.

If you produce the same power at a higher rpm, the torque required to produce that power is reduced and consequently the stress on the trans is reduced.

Comparing engines of similar displacement and similar bolt-on components, IDI engines typically produce less torque for most of the torque curve but the TDI torque curve drops off sooner so at higher rpms the IDI engines will produce higher torque than the TDI's. Stock TDI engines are all intercooled which increases torque throughout the entire curve. Most stock TDI engines have been fitted with VNT turbos which typically produce boost at lower rpms and across a larger rpm range than similar wastegated turbos, adding to the low-end torque.

So... all that in mind, generally the IDI engines are easier on transmissions because generally they produce less torque and produce peak torque and peak hp later in the curves. Whether one engine is specifically harder on the trans than another depends on how those specific engines are set up.

[crazyvwvanman]

What tencentlife wrote applies to your case. The higher running rpms of the AAZ means less torque on parts of the tranny at the same road speeds compared to TDI.

It is simple math as he shows. Gearing too tall and keeping in a tall gear at high engine loads means higher stress and less lubrication, at the same time. Of course with fewer combustion events to make the same amount of HP means each combustion event must be stronger, so more stress again with less lubrication.

So running at high torque and low rpm pounds the tranny and it doesn't live as long.

Mark

[Sodo]

[Zeitgeist 13]

Pixie dust.
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[danfromsyr]

most often applied to cranks and journals but I see this as relevent in the loads presented to high loading transaxles.

Oil SHEAR in the mainshaft bearings and gear mating surfaces..

heavy loads, low rpms and high torque push the oil out of the way, creates more friction and generates 'pixie dust' which compounds the issues.

for more info on oil shear
https://www.bobistheoilguy.com/effects-of-shearing/

https://www.truckinginfo.com/154928/the-lowdown-on-the-new-low-viscosity-oils

again just IMO, from an uneducated poorly informed fella.
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[Sodo]

[tencentlife]

[Sodo]

[Howesight]

[AndyBees]

Well, the DMF is heavier than a SMF such as the G60 which also uses a 228mm clutch disc. And, the SMF is substantially heavier than the OE flywheel with the 215mm disc.

So, I suppose a DMF, using a sprung clutch disc, would be the best off the shelf choice.

My tranny was subjected to all those flywheels in reverse of the order I listed, with the DMF being in place for probably less than 10k miles of the total 82k miles since I built the tranny.

By the way, I have changed the oil in my tranny numerous times with most of the changes in the first 15 to 20k miles and most recently when I installed the DMF..
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[tencentlife]

[ianNJ]

Super interesting. Thanks guys and the OP. I recently shipped my van down to get a TDI common rail. The trans was the question on what we’re going to do to it. The trans is currently with Matt Steedle. He has been fantastic to work with so far, way better than the other couple companies I talk to. The other company is pretty much expected me to tell them what I wanted. Matt actually helped me work through what I wanted, what he thought I might need based on the horsepower and torque. It was decided we’re going to do a full build on the trans including ring and pinion equally spaced out gears aluminum parts etc. etc. We are setting the gear ratios for my current tire set up and the fact that most of my driving is going to be in town’s highways and potential start and stop traffic on highways. No rockclimbing for me ...

SODO- basically your post was what Matt had to say that there are so many individual variables that are never talked about. Like the folks that say the TDI burned up their trans but they never change the oil and it had 240,000 miles on it before they ever got the new engine ...
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[Sodo]

[tjet]

On the TDI, how about installing a larger turbo so the boost comes in later in the RPM range?

[?Waldo?]

Assuming an eTDI, a turbo swap would be the hard way to do it. The turbo boost pressure is fully computer controlled and adjusting the map is easily done by any tuner. Reducing boost and/or fuel for any given rpm range is easily doable.

[tjet]

If I do decide to do a diesel swap, it will be an M-TDI AHU.

Would this 20/52 spool up higher in the RPM vs a stock turbo?

Maybe a bigger "laggy" turbo would be easier on the trans?

https://www.idparts.com/garrett-2052-turbo-p-2597.html