Rear Main Seal

[DANTIP]

The rear main seal on my '72 K20 (350/TH350) has been leaking and I've decided to swap it out. Here's my proposed plan, please share feedback/suggestions. I'm not sure if the starter needs to be removed? Not sure I even need to raise the engine (the 4x4 cross-member may be low enough to get the pan off)?? Those who have done this on a 72-vintage 4x4, please review my steps and provide suggestions/tips. The truck is thankfully on a lift, which provides excellent access/safety.

1). Disconnect battery.
2). Rotate engine with strap wrench until timing mark points downward
3). Drain oil from pan/remove oil filter.
4). Remove distributor cap.
5). Put jack under balancer.
6). Remove bolts from motor mounts.
7). Remove Transmission/transfer case mount bolts.
8). Raise the front of the engine a few inches while checking the clearance between the distributor and firewall. Also watch fan to shroud clearance.
9). Remove oil-pan bolts.
10). Remove oil pan.
11). Remove oil pump while noting position of shaft.
12). Remove rear main cap.
13). Remove seal 1/2 from cap.
14). Clean cap.
15). Use wood dowel to start to drive seal 1/2 from block.
16). Carefully grab block seal 1/2 with pliers and rotate/remove.
17). Inspect Crank seal-area for wear. If fingernail can detect a ridge, I'll use an offset seal, otherwise, the standard seal.
18). Clean all gasket/sealing surfaces.
19). Check pan for any distorted bolt areas. Straighten if needed.
20). Install Felpro 1-piece oil pan gasket onto pan using dental floss on a few bolt holes to keep the gasket in place.
21). Install seal 1/2 onto cap (confirm orientation of oil-side) with 1-side approximately 1/8" above the cap surface (this is supposed to help prevent leaks due to alignment with the cap/block).
22). Apply light coat of engine oil on the seal.
23). Install the block 1/2 of the seal using the seal guide strip that prevents the sharp edge of the block from damaging the seal during installation.
24). Rotate the seal into place leaving the corresponding 1/8" seal offset.
25). Install the main cap using 3-step torquing.
26). Install the oil pump and torque fastener.
27). Put a small amount of sealant at the (2) edges where the timing cover intersects the block and at the (2) edges where the rear main cap intersects the block.
28). Move pan into place with the 1-piece gasket. Try to avoid the counterweights.
29). Start a few pan bolts and cut/remove the dental floss ties.
30). Install remainder of pan bolts and torque.
31). Lower engine.
32). Reinstall motor-mount bolts.
33). Reinstall transmission/transfer case mount bolts.
34). Reinstall distributor cap.
35). Add oil/filter.
36). Attach battery cable.
37). Start/test/Pray.

[Rickysnickers]

I can't add anything helpful, but that sure is a clean truck!!

[AussieinNC]

The starter should be removed...

When installing the new oil seal, I always lightly lube the lip of the seal to prevent burn up on startup...

Make sure your pcv system is working fine...a blocked up system will pressurize the sump and cause all sorts of oil leaks...

[MySons68C20]

I like #21.....imho the best way to install 2 pc seals

[72Cheyenne454]

Hi Dan,

I'm sorry to hear the rear main is leaking. I installed a new rear main seal, just as you described above, when I restored that truck. I can't remember if I installed an offset seal in it, or not.

You might consider raising the engine just enough to pull the engine crossmember out. The crossmember is easy to remove and it'll make getting the pan in/out a lot easier.

If you do decide to raise the engine, be cautious of the upper radiator hose. The rubber on both ends of that steel upper rad hose is pretty stout and may not provide enough flex, which could possibly damage the rad upper house outlet.

There's also conflicting opinions on using a small smear of RTV on the seal halves where they meet. I've always done it this way with success... until your truck... sorry.

Miles

[DANTIP]

Originally Posted by 72Cheyenne454

Hi Dan,

I'm sorry to hear the rear main is leaking. I installed a new rear main seal, just as you described above, when I restored that truck. I can't remember if I installed an offset seal in it, or not.

You might consider raising the engine just enough to pull the engine crossmember out. The crossmember is easy to remove and it'll make getting the pan in/out a lot easier.

If you do decide to raise the engine, be cautious of the upper radiator hose. The rubber on both ends of that steel upper rad hose is pretty stout and may not provide enough flex, which could possibly damage the rad upper house outlet.

There's also conflicting opinions on using a small smear of RTV on the seal halves where they meet. I've always done it this way with success... until your truck... sorry.

Miles

Thx for the guidance! I'm absolutely thrilled with the truck, the leaking seal is a minor thing to me. I have owned probably 30 very nice collector vehicles since my teen years and I have to admit the truck you restored and sold to me gets the most attention BY FAR!!

I've driven the truck almost 5,000 miles over the past few years and it still looks like a fresh restoration. My grand daughter LOVES the truck!!

Great work Miles!!

Dan

[72Cheyenne454]

Originally Posted by DANTIP

Thx for the guidance! I'm absolutely thrilled with the truck, the leaking seal is a minor thing to me. I have owned probably 30 very nice collector vehicles since my teen years and I have to admit the truck you restored and sold to me gets the most attention BY FAR!!

I've driven the truck almost 5,000 miles over the past few years and it still looks like a fresh restoration. My grand daughter LOVES the truck!!

Great work Miles!!

Dan

Thank you, Dan. I really appreciate your feedback and I'm glad to hear you're still happy with the truck. Thanks for the pics... it looks awesome!