What is the torque spec for the transmission to engine bolts?? And a bolt question... - PeachParts Mercedes-Benz Forum

pawoSD · #1 07-17-2008, 01:33 AM

Soon I will be reattaching our donor engine to our transmission that is in the shop.....my main question is, what is the torque spec for the bolts between the trans and engine?

And, the geniuses that last worked on the car felt it unnecessary to re-install the top two trans to engine bolts, so they are gone, and we don't have any....does anyone know what size/part number from the EPC net they are? There are three different bolts listed as used to couple the two together, but it doesn't give the size or part number of what goes where....we ordered one bolt from the dealer to check it, and it looks like it might be the right one, but I'd like to confirm what length should go in that spot....as well as the thread style....is there a smooth portion of the bolt with threads at the end? or is it all threaded?

Any tips or solutions would be greatly appreciated....this is essentially the only thing I am unsure of out of everything that I'll be putting back together.

sixto · #2 07-17-2008, 01:44 AM

EPC says it's one of three bolts but isn't specific about which goes in the top two positions.

My rule of thumb is to use the same length bolt that works where the transmission flange has a similar thickness and goes right into the block; i.e., doesn't go into the starter or a nut or anything but the block.

Measure the depth of the hole in the block with a rod to determine how long a bolt can be then make sure you have at least 1cm of engagement. That should narrow it down to one of the three available bolt lengths.

Sixto
87 300D

DeliveryValve · #3 07-17-2008, 02:05 AM

IIRC the top bolts are 70mm in length and with a 17mm head. But as far as thread, I don't remember the spec.

The torque figures are as follows.

transmission to engine:
M10 bolts 41ftlbs (55nm)
M12 bolts 48ftlbs (65nm)

Got this from this thread.

turbobenz · #4 07-17-2008, 02:07 AM

no junkyards near you?

lowriderdog37 · #5 07-17-2008, 10:35 AM

From my experiences there are only 3 torque values that are relevant: finger tight, motorcycle tight, and upper limit. I went with the last on this one when I did mine.

Unfortunately, I don't remember which bolts went in the top.

pawoSD · #6 07-17-2008, 11:10 AM

Quote:

Originally Posted by turbobenz

no junkyards near you?

Yes, but.....

Think of the effort required to extract those two bolts from a car laying in the mud at the junk yard.....and it would end up costing nearly as much as getting new bolts.

winmutt · #7 07-17-2008, 11:55 AM

Bolts on th top are *not* threaded the whole way iirc. Good n tight is the torque spec. Similar to the manifold. Highly un German.

pawoSD · #8 07-17-2008, 01:58 PM

Quote:

Originally Posted by DeliveryValve

IIRC the top bolts are 70mm in length and with a 17mm head. But as far as thread, I don't remember the spec.

The torque figures are as follows.

transmission to engine:
M10 bolts 41ftlbs (55nm)
M12 bolts 48ftlbs (65nm)

Got this from this thread.

The bolt we ordered (and have) is a 17mm head and is 80mm in length....is that it? It is threaded for the last 30mm of the bolt or so, the rest is smooth.

The EPCnet is very unhelpful with this stuff.....does anyone have a book or FSM that gives it in better detail? The computerized FSM doesn't cover trans work....

On a brighter note, the trans (which is at the shop) was inspected and found to be in excellent shape inside....so they are replacing the external seals and we'll have it back Tuesday! $250 ish! Sweet.

DeliveryValve · #9 07-17-2008, 03:23 PM

Quote:

Originally Posted by pawoSD

The bolt we ordered (and have) is a 17mm head and is 80mm in length....is that it? It is threaded for the last 30mm of the bolt or so, the rest is smooth.
.....

No it will not work. It is too long and you'll bottom out with 10mm left. The 80mm bolts IIRC are for the side of the bellhousing. The 70mm bolts physically look similar to the 80mm.