EM6-300L flywheel housing replacement

[dieselfuelonly]

We have a RD690S with an EM6-300L that has a cracked flywheel housing.  Found a good used replacement, 2 questions.  When I pulled the old one off there was no gasket between the block and flywheel housing, just some RTV.  It's been off before, apparently someone tried to weld the cracks in the past.  Does a gasket exist, or just use RTV or some other sealant?  Our Mack parts guy hasn't been too helpful on this old truck.  Also, since this isn't the original flywheel housing that came with this engine, do the dowel pin holes need to be reamed and oversized pins installed, or if the fit is tight just roll with it?  Thanks for any advice.

Edited April 27, 2021 by dieselfuelonly

[mrsmackpaul]

Dunno about a gasket but I wouldn't of thought there would be one

The dowls I would imagine would be all machined to a precise measurements in the factory and should be interchangeable 

Thats my thoughts 

 

Paul 

[Joey Mack]

OK..... The sealant is Mack Gray! also, that fly wheel housing may need to have "Runout" checked.... put the housing up dry to check and set run-out... if needed on this engine. I have done this only a few times many years ago... I hope "F", and Glenn chime in. There is others that can tell you as well.... jojo

[Vmac3]

From what I remember, if you are replacing the flywheel housing, the engine block has to be cleaned and the dowel pin needs to be removed. If the block is not absolutely clean then your readings will definitely be off. You install the new housing up dry, tight enough so it wont move but loose enough so you can make adjustments. Put a magnetic base dial indicator on the crankshaft and with a long enough stylus measure the total indicated runout. Adjust the flywheel housing to spec. If the runout is in spec (max if I remember it is around .007"of runout) check to see if the dowel pin hole is aligned. If it is then you are good to go. Install the housing using the Mack grey silicone. If not while the housing is on the engine, you have to drill out the dowel pin hole on the flywheel housing and install an oversize dowel pin. I printed and saved the part numbers for oversized dowel pins from somewhere. As Joey indicated make sure you use the Mack Grey silicone.  If this procedure is not done carefully then your rear main seal will leak.

Here you go.

183GC192-P1 with pin size (0.623–0.624)

183GC192-P2 with pin size (0.639–0.640) and hole size (0.637–0.638)

183GC192-P3 with pin size (0.656–0.657) and hole size (0.654–0.655)

183GC192-P4 with pin size (0.686–0.687) and hole size (0.684–0.6585)

V

[h67st]

Before you remove the dowel pins, clean everything and install dry like Vmac3 says. Check the runout, if it's within spec you're good. If not, follow Vmac3's instructions. I had a bar made at a machine shop to bolt to the crank that held my drill good and square.

[Rob]

The only one of these I've ever seen out of spec was a Maxidyne engine rebuild with a later aluminum flywheel housing incorporated. The fasteners retaining the flywheel housing to the block were not used with a thread locker and given the thermal expansion differences between aluminum and cast iron, they worked loose. In fact the flywheel housing being softer than the dowel pins was destroyed. A replacement cast iron flywheel housing was slipped onto new dowel pins and it was within circular runout tolerance upon reassembly and never another problem. This was a Fuller transmission install and owner operator end dump truck application.

Never was a fan of aluminum flywheel housings myself except on maybe a two stroke Detroit engine which did not have the "off idle" torque rise of others. There is a lot of torque absorbed through the flywheel and clutch housing upon acceleration and the fasteners need to remain tight to absorb it.  

[h67st]

16 minutes ago, Rob said:

The only one of these I've ever seen out of spec was a Maxidyne engine rebuild with a later aluminum flywheel housing incorporated. The fasteners retaining the flywheel housing to the block were not used with a thread locker and given the thermal expansion differences between aluminum and cast iron, they worked loose. In fact the flywheel housing being softer than the dowel pins was destroyed. A replacement cast iron flywheel housing was slipped onto new dowel pins and it was within circular runout tolerance upon reassembly and never another problem. This was a Fuller transmission install and owner operator end dump truck application.

Never was a fan of aluminum flywheel housings myself except on maybe a two stroke Detroit engine which did not have the "off idle" torque rise of others. There is a lot of torque absorbed through the flywheel and clutch housing upon acceleration and the fasteners need to remain tight to absorb it.  

I'm with you, seems like with all the stress between engine and transmission an iron housing would be best.

[Joey Mack]

I forgot to ask about a separate rear main housing. just curious. still need to do the runout check for the alignment of the clutch and tranny... I'm glad the others posted on this topic.. jojo