M20 auto to manual zf swap

[hopeful]

Hello everyone, I've got an '88 auto e30 that I'm trying to manual convert. Seeing as how a near 40yr old trans with 300k was going to cost me 1800$ for the full swap I decided to go the ZF310/320 series route. The cost plus I feel the gearing the zf offers better suits my application (s3.73 out back), it's just a weekend cruiser that will hopefully see 2-3 track days per year, and we'll go from there😁.

The questions I've got (after plenty searching/ research) is the parts compatibility. I picked up what I've been told is a zf from a E46 328 with the front half of the drive shaft. I plan on getting the rear half from any other e36 excluding the 318.

I plan on purchasing a flywheel from RHD and a new clutch kit for an m20. I'd suppose I need new bolts, are there any spacers I'd need?

I still need to purchase from an e30 a pedal set, trans xmember with e21 mounts, and shift carrier rear bracket.

What modifications are required to the shift carrier?

Has anyone got any advice? Your input is greatly appreciated as I'd like to start tearing everything apart but once I'm sure I've got all the parts I can't easily order from rock auto.

[mtech325]

The ZF 5-speed with a 3.73 isn't going to be fun without an overdrive if you do any highway driving, for that you'd want something in the 3.15-3.46 range.

For the clutch & flywheel setup, there are a couple ways to do it: You can use the m20 clutch & flywheel (and starter), but use the e21 323 throw out bearing to make up for the stack height of using a single mass flywheel in a dual mass transmission. For the slave cylinder and pilot bearing you'd use the e36 ZF parts. The other option is to use e36 M3 clutch and flywheel (can do do LTW version as well) plus the e36 starter, which keeps things simpler for ordering parts and remembering what combo you used.

For a more plug & play driveshaft, you can use the e36 m3 5-speed 4-bolt/328 e36 5 speed driveshaft with e30 CSB for your year chassis.

Shift linkage can be e36 ZF, but will be tilted to the left due to the m20 vs m/s5x engine angle differences. Otherwise the alternative is a top mount style shifter which eliminates the need for the carrier. Transmission brace will need to be custom to account for tilted transmission angle (not unlike what's used for the g260 24v swap setup).

[Panici]

I'd shoot Rama from RHD an email and explain what you are trying to do.

I found him quite helpful in working out the best combination for my car. Have used his flywheel successfully with two different clutch and trans setups now.

[hopeful]

Thanks for the detailed replies guys, all things worth noting. Will email him prior to purchase.

Really considering the chassis mounted shifter, just don't know how bearable the nvh will be..

[varg]

The ZF 5-speed with a 3.73 isn't going to be fun without an overdrive if you do any highway driving, for that you'd want something in the 3.15-3.46 range.

I'd say 3.46 is too high, that gives a 5th gear ratio which is basically equivalent to a 4.27 with a G260. Assuming stock tire height you'd hit 70mph/113kph at around 3,400rpm in 5th gear, no good if you're going to do highway driving. As long as the M20 is going to remain NA or only get a fairly small turbo I'd put a Getrag 240 behind it. I had a G240 with my turbo M42 and it had no issues holding way more torque than an NA M20 makes, and won't require a change to the final drive ratio or any odd combinations of parts in the bellhousing; M20 stuff would work just fine.

I would not use a chassis mounted shifter in a street car, or without very stiff engine and transmission mounts.

[Panici]

As some datapoints, I have a 3.91 + ZF320 5-speed in my E36, and it spins at 4k cruising down the highway.

Drove my E30 with a 3.73 + ZF320 for about 500km before I switched it out.
Went with a 2.93 + ZF320 in the E30 and things are much better for highway cruising. But that is a turbo application so I was willing to gear the car higher and lose some mechanical advantage.

I would not use a chassis mounted shifter in a street car, or without very stiff engine and transmission mounts.

Curious as to why people say this?

I have OEM rubber engine and trans mounts and my chassis mounted shifter works great. No noticeable NVH that I can discern.
Maybe it helps that my shifter throw is adjustable, and that I have modified things to place it where I want?

[jbontke]

As some datapoints, I have a 3.91 + ZF320 5-speed in my E36, and it spins at 4k cruising down the highway.

I have OEM rubber engine and trans mounts and my chassis mounted shifter works great. No noticeable NVH that I can discern.
Maybe it helps that my shifter throw is adjustable, and that I have modified things to place it where I want?

I have the same chassis mount shifter in my car with a g260. No NVH

How do you like the CRS shifter with the ZF trans? I am not a big fan of it with the g260. A very worn g260. Temped to go back to OEM shifter parts. I have a ZF320 that will be installed this year with a S52. Maybe the ZF trans will be better with the CRS shifter?

[Panici]

I have the same chassis mount shifter in my car with a g260. No NVH

How do you like the CRS shifter with the ZF trans? I am not a big fan of it with the g260. A very worn g260. Temped to go back to OEM shifter parts. I have a ZF320 that will be installed this year with a S52. Maybe the ZF trans will be better with the CRS shifter?

I love it.
I was previously running the G260 with a "New" style shift carrier conversion and 1.9 z3 short shifter. This is a big change in the right direction just as the 1.9 z3 was a big upgrade from the stock lever with sheet/plate style carrier.

Made a difference to adjust the throw length properly. I have positive engagement in all the gears vs when I first installed. It was at default (shortest?) throw length and made it hard to distinguish all the gates, in addition to requiring too much effort to shift.

Still going to cut and lengthen the DSSR to get the pattern a little closer to the dash. Wanted to drive the car a bit first with my preferred seating position.

It's great that the shaft is all steel, so I can shorten if needed. Going to get the fore/aft position correct and then see if the height is where I want.

[hopeful]

As some datapoints, I have a 3.91 + ZF320 5-speed in my E36, and it spins at 4k cruising down the highway.

Drove my E30 with a 3.73 + ZF320 for about 500km before I switched it out.
Went with a 2.93 + ZF320 in the E30 and things are much better for highway cruising. But that is a turbo application so I was willing to gear the car higher and lose some mechanical advantage.



Curious as to why people say this?

I have OEM rubber engine and trans mounts and my chassis mounted shifter works great. No noticeable NVH that I can discern.
Maybe it helps that my shifter throw is adjustable, and that I have modified things to place it where I want?

Because all the engine/ trans rotation is now directly attached to your chassis through the shifter, I wouldn't want all that force acting on the transmission tunnel, it's likely to tear something, maybe? That's the theory anyways. All the nvh is due to the stiffer required mounts, if they're not there then no increase in nvh.

I've decided against a chassis mounted for this reason, solely.




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[varg]

Not sure why one would assume the concern is NVH? You won't get much noise or vibration through a chassis mount shifter, there is still some isolation between the linkage and the body of the car unless it's a metal on metal spherical bearing setup. I have seen chassis mounted shifters in E30s moving all over the place under acceleration and maneuvering if they aren't coupled with stiff mounts, that's enough for me. I have stiff poly mounts in my cars but I still opted for a rebuilt OEM setup with DSSR and poly carrier bushing.

[hopeful]

I'd say 3.46 is too high, that gives a 5th gear ratio which is basically equivalent to a 4.27 with a G260. Assuming stock tire height you'd hit 70mph/113kph at around 3,400rpm in 5th gear, no good if you're going to do highway driving. As long as the M20 is going to remain NA or only get a fairly small turbo I'd put a Getrag 240 behind it. I had a G240 with my turbo M42 and it had no issues holding way more torque than an NA M20 makes, and won't require a change to the final drive ratio or any odd combinations of parts in the bellhousing; M20 stuff would work just fine.

I would not use a chassis mounted shifter in a street car, or without very stiff engine and transmission mounts.

I really did consider the m40 swap as someone was selling one locally for a much lower price point, I just felt it had the same cons given its age/ torque rating/ unreplaceableness. I figured I go ZF once I won't have to look back now or ever. Rear ratio's may have to be adjusted but really I don't plan on doing much highway driving at all, after all this is a now nearing 40 yr old classic I'm definetly not commuting with it etc.

AHH I GET IT NOW... I really thought it would be real requirement to get the poly mounts with the chassis shifter, and then seeing things like this friends experience (https://youtu.be/I7LUDPx-LD4) scared me away indefinetly. I see that technically you don't NEED poly mounts with the chassis mount shifter, you'll just see the shifter moving a lot more under load...

[Panici]

Because all the engine/ trans rotation is now directly attached to your chassis through the shifter, I wouldn't want all that force acting on the transmission tunnel, it's likely to tear something, maybe? That's the theory anyways.

I don't see how that would be the case, unless your shifter pivot point is binding at the limit of it's travel.

Maybe my shifter is of a different design then the others on the market? Seems to be plenty of travel in every direction.

[varg]

You would not ever break a getrag 240 with an NA M20, but if they're hard to find that's a shame because they're really a better solution if you can keep your gearing on a budget. You would even be able to use a 318is driveshaft and (modified) linkage; very easy. I have two unused G240s collecting dust in my garage , I would expect them to be common up there but I guess not. As for that video, the M20 is incredibly smooth compared to the M42, so your friend's experience with poly mounts shouldn't be as much of a factor for you, my car is hardly the pinnacle of low NVH with UHMW bushings, 200TW tires and coilovers, but I have zero issue with my poly mounts. When you go straight from an M42 to an M20 the difference in vibration feels like going from a gas powered string trimmer to an electric one.