300SD Engine Swap Info. - PeachParts Mercedes-Benz Forum

bio350 · #1 12-16-2008, 08:48 PM

I pulled the 3.5 "rodbender" out of my 1992 300SD (140 body type) and put in a 3.0 six cylinder. It runs great, except, I am having trouble with the transmission. It is stuck in 2nd gear and will only manually shift 2nd to 3rd but not automatically. It also "clunks" really hard when going into Reverse or Drive. Prior to the swap the transmission worked beautifully. Unfortunately I did not swap both. A local mechanic told me that this swap will not work because the engine will not "recognize" the transmission.
Does anyone out there have any information about this?
It was a difficult swap and required some creative thinking to get the engine to mount in the compartment, so I hate to throw the whole project in the trash.

CSchmidt · #2 12-16-2008, 09:28 PM

We have a member here "Sixto" that did this swap successfully about 2 years ago. Look for some of his posts. He watches here pretty often and may answer as well. Good luck, I may be doing the same thing soon.

bio350 · #3 12-16-2008, 09:40 PM

Thanks. If you need any info on the swap, let me know. It required some modifications to get the motor to fit. But, I did it all myself in my driveway.

LUVMBDiesels · #4 12-16-2008, 09:51 PM

Try this...

Check the vacuum lines as they control the harshness of the shift. also adjust the bowden cable (cable attached to the accelerator linkage. If it is too loose the shift points will be too high. Try tightening it and see what happens.

babymog · #5 12-16-2008, 09:57 PM

I'm surprised that you couldn't use the 603.971 mounts on the 3.0L block. Is there a difference in the mounting bosses on the engine from '91 to '92 (603.970 - 603.971)?

Which 3208 is in your MH? The 300hp 3208ATAAC?

BTW, if you need a '91 transmission, I'll make you one hellova deal.

bio350 · #6 12-16-2008, 10:07 PM

I will recheck the vacuum lines. That was my initial thought. Vacuum produced from the 3.0 but using the transmission that was matched with the 3.5. Not sure if there is a difference.
I had to use the engine mounts from the 3.5 but there were holes in the 3.0 already matched up for them. The modification was that I had to manufacture an oil pick up tube and use the oil pan off of the 3.5 and put it on the 3.0, otherwise the oil pan would rest on the cross member.
My motorhome has the 300hp 3208.

sixto · #7 12-16-2008, 10:21 PM

Sounds like the bowden cable is kinked or adjusted too tight.

Did you keep the exhaust manifold and turbo of the 3.5? Sounds like you didn't if you had to customize oil supply and return lines.

I swapped only the 3.0 short block because all I bought from Hit Man X was a .961 short block. Everything else was from the 3.5. It's really plug-n-play. Biggest custom job was converting the 3.5 turbo to a pressure actuator. Transmission shifted fine before and after.

Sixto
87 300D

bio350 · #8 12-16-2008, 10:45 PM

I completely stripped everything off the shortblock and took everything off the 3.5 and put it on the shortblock. The 140 body style would not allow for the any other type of exhaust and thus turbo. Plus, the turbo was brand new off the 3.5. The previous owner had gone through all the usual dealer diagnoses before telling him the engine was bad.

sixto · #9 12-16-2008, 11:03 PM

I reread your post. You had to tweak the oil pick up tube for the oil pump. I used the 3.5 pump in the 3.0 block precisely to avoid having to replicate the distance between the 3.0 pick up and the internal bottom of the 3.5 sump. The 3.5 windage tray serves as a mounting spacer of the oil pump which is another concern. Larry Perkins believes the windage tray is the root of all evil in the world. Other than windage tray nuts coming loose, which only Larry reports as having happened, I don't know why it would be a problem. I'm not saying it's not, I'm just saying I know nothing about this.

I didn't look into transferring the 3.5 pick up to the 3.0 pump. 3.5 oil pressure was good and 3.0 oil pressure was unknown other than crank and rod bearing clearances within installation spec, so I doubt I could have gone wrong either way.

You can mount the slimmer 3.5 wastegate on the 3.0 turbo and clock the center section if both are T3s to have 50 trim with .971 exhaust. I don't know how far out of place the turbo inlet will be for air cleaner hose fitment but the inlet flange diameters are the same. Doesn't matter if you kept the 55 trim.

I'm surprised you say it was a difficult swap. I did this in my inclined driveway and it was plug-n-play as mentioned. The upper transmission bolts are a b!tch to get to with that metal conduit in the way but you'd have to deal with that swapping in another .971 engine. Doesn't help to swap engine and transmission because it would be more work to pull and reroute the starter cable/s that run through that conduit.

Sixto
87 300D

bio350 · #10 12-16-2008, 11:12 PM

I guess it wasn't that difficult. It's just that I didn't think before I put the motor back in and once I had it in, I realized the oil pan was not going to allow the motor to sit down on the mounts. It was actually resting on the cross member. So, I took it out and tried to swap oil pans but the pick up tubes were different. I fondly remember one of my kids stories called "When You Give a Mouse a Cookie". In this case my wife said something like, "When you allow your husband to buy a Mercedes....".

larry perkins · #11 12-19-2008, 10:21 AM

pictures replace words, brian carlson placed the pictures of the baffel bolt,washer damage to the 350 sdl engine on this site probably 2 years ago.
i took um, brian posted um.
larry perkins
ps since then i have had 2 more engines with same problem,got to another early enough and onyl one bolt had dropped out,others were hand tight,removed with hand,no wrench.

pawoSD · #12 12-19-2008, 01:19 PM

The mechanic who said the engine would not "Recognize" the transmission doesn't have a clue. The driveline on the older cars (and up till 1996) is purely mechanical/vacuum controlled. The engine/trans could care less whats attached to them. A trans issue is usually bowden cable adjustment, vacuum modulator adjustment, or some other issue with the trans itself.

bio350 · #13 12-19-2008, 04:59 PM

I jokingly asked him what do I need to do, set up a meet-n-greet or get one of them drunk+ He kind of laughed, but then began in about the computer. I told him the 92 diesels didn't have them and he was sure they did. I have since stopped calling him for info....maybe that's what he wanted.
Anyway, thank you for all the help. As soon as it warms up enough for my fingers to work on cable adjustments I will roll back under that thing.
In the mean time I may be unloading my 91 350SD with dying "rodbender" and I have an 87 300SDL that I was going to pull the motor and do a swap. Have not officially decided yet. But, I'm getting to the end of my rope on these Mercedes.
I just had to do the tie rods on my wife's 95 E300 yesterday. Too many other projects, like eating, sleeping and earning an income.

sixto · #14 12-19-2008, 07:32 PM

Ask him to point out the transmission computer. It might help if he looks for electrical connections in the transmission. Aside from the single pin connection to the kickdown solenoid, there won't be any. I don't know if the 140 has an NSS attached to the transmission or if it's all handled in the shifter mechanism. Regardless, the NSS doesn't connect electrically to the transmission. Maybe he'll say ZF was a Bluetooth pioneer

Bowden cable adjustment is done from above the engine.

Sixto
87 300D

bio350 · #15 12-23-2008, 03:59 PM

UPDATE!!!! The rain stopped, the wife stopped Christmas shopping and I got a break from my real job, so I had a minute to adjust the Bowden cable. IT WORKS!!! The transmission shifts great!!!
Thanks for all the info and help...I'm sure I'll be asking for more.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode