190D 2.5 Turbo Question

[dbenz]

Will a manual transmission from a '86 190D 2.5 bolt/fit on a '87 190D 2.5 Turbo? Just love shifting, especially when it's a diesel.

Thanks in advance for the correct answer -- David

[jobah]

Good question. I have also wondered this. It would, to me, be the best set-up.

It should just bolt on (along with the clutch components).

[danalinscott]

I too want to convert my auto tranny 2.5 to a manual shifter.

jobah..are you saying that you know a manual tranny will "bolt right up" for sure..or are you "wondering".

I would love to participate in a "joint" research project on this. I asked the same question last summer..and got no real answer.

I don't think anyone on the forum (or any of the other forums I asked on) has actually done this. So I have been gathering info for the last 6 months hoping to have enough info to "go for it" this summer.

The 2.5 turbo 190 is as close as I can come to a diesel powered "sports car" I think....it just sucks having to be stuck with an auto tranny in it.

So if you two any any others would like to join the research team...please comment.

The more brain weight working on the project the better.

[jobah]

Here is my thought,

THe block of the 2.5 turbo is the same as the block of the 2.5 non-turbo as far as length and mounting position. The tranny from the 2.5 5 speed should just bolt to the turbo. Thus, the drive shaft from the 2.5 5 speed should be the right length for the 2.5 turbo engine.

The rest of the clutch components are easy, as the body is already configured to receive clutch components in the cabin.

I am 99% certain the set-up is mechanically possible. I do not know the performance and feel of a turbo with a 5 speed in a diesel. I would love to find out.

[danalinscott]

Ok..time to start looking for a "donor vehicle".

It actually looks like a fairly simple conversion if one can find a 190D 2.5 with bad body/engine. I wonder if a 300 2.5 trany will work..or a 2.2 with an upgraded clutch? Need to spend $50 on a parts interchange book.

A cherry picker, air tools, and a wekend...maybe two are all that should be required.

Pull the engine/transmission from both vehicles.

Jack and block both vehicles.

Add new throw out bearing, pressure plate, slave cylinder, and clutch disc to donor tansmission.

Bolt up manual tranny to engine/bellhousing.

Check to make sure the driveshafts are the same length...and swap if not.

Swap tranny mounts, center consoles, and pedals.

Replace engine/tranny in vehicle...bolt up all.

Sshift boot...etc.

Test drive

Have I missed something?

Oh yeah...salvage anything useful from the donor..and call the nearest salvage yard for pickup.

Is there more?
I'm starting a search. If I find more than one I'll post.

Most engines I've seen between auto and manual have had different flywheels. The torque converter takes up the difference in weight between the two.

Are the flywheel and engine balanced seperatly or as a unit?

[danalinscott]

Good point. Probably need to swap the flywheel (and ring gear if it looks less chewed).

The flywheel should be balanced OK...separate from the rest of the engine.

I suppose I shoud invest in one of the CD manuals to actually see the difference between the auto and manual 2.5 configurations.

[md21722]

Its been my understanding MB manual transmissions are NOT designed to handle the power of a turbo diesel engine?

[danalinscott]

That MAY be true..but does not make sense to me.

The gas engines that fit in a 190 have MORE HP than the deisel models. And so the transmissions shoudl be able to take MORE than the diesel engines. This should be true for even the "mighty" 123 or so HP the 2.5 turbo dishes out.

Same should go for the clutches.

And it seems to me that a manual transmission from a NA 2.5 should be capable of taking the additional 30 or so HP that the turbo model has available since at the low rpms that the cluthc is engaging at the 2.5 turbo and NA should both be producing about the same HP/torque. Once the turbo kicks in the clutch should be fully "locked up" and unless it slips under accelleration..which I think is unlikely if it uses the same clutch as a more powerful gas model..I can't see why they could not easily handle the output of a diesel engine.

Man..I need to get that parts dross refference guide. It would help answer these questions more definatively.

[MonsieurBon]

I thought the concern was the high torque output from a turbo-diesel, not HP.

still sound like a fun idea to me, though!

[190D22]

Would the two cars be ratio'd differently?

[BlueBabyBenz]

I've been wondering this myself.

I have a NA 190 2.5 with a (probably) dead Automatic Transmission.

I've been quoted $3000 Canadian for a rebuild tranny. For that money, I'd like to put in a 5 speed, and I was thinking, hey, while I'm at it, I'd see if a turbo engine was available as well.

[md21722]

The 190D 2.5 Turbo has 2.65's, the 87 2.5 NA has 3.07's.

Brian

[danalinscott]

The 190D 2.5 Turbo has 2.65's, the 87 2.5 NA has 3.07's.

Is that the transmission ratio, the differential ratio, or the final/combination ratio ?



And as I see it the 2.5 NA and turbo put out about the same tourqe untill the turbo "kicks in" at around 2000 rpm. By the time the engine is at that rpm the clutch should not be slipping..and so is fully "locked up" unless there is enough additional torque/hp when the turbo kicks in to actually cause the clutch to begin to "unlock" the clutch should be ok.

As far as the tranny is concerned...the torque should not be a major condiseration. Especially considering that MBZ tends to "overbuild" everything...

[md21722]

Rear axle ratios 2.65's for the turbo, 3.07's for the NA. Last time I read about this someone was interested in putting a manual tranny in a 603 turbo diesel and it came out that the manual tranny was not built for the power of the turbo engine, but was fine for a 603 NON-turbo diesel.