Author Topic: Rear main replacement method.  (Read 542 times)

Offline 1987_Rabbit_Hole

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Rear main replacement method.
« on: January 12, 2022, 01:36:23 PM »
Hey guys
I have an 87 V10 with a leaky rear main seal I’m going to replace.  My question to you guys is if you had the resources to do it either way, would you pull the engine or do it under the truck?  I don’t have a lift.  I have a couple of floor jacks l, some stands and a cherry picker.  Seems to me by the time I wrangle the tranny and xfer case around enough to get in there and then hook it all back up, I could’ve just as easily pulled the motor and done it.  What’s your thoughts?
« Last Edit: January 12, 2022, 01:46:38 PM by 1987_Rabbit_Hole »

Offline JohnnyPopper

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Re: Rear main replacement method.
« Reply #1 on: January 12, 2022, 04:58:06 PM »
Ugly either way, but with your setup, I would pull the engine.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline Shifty

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Re: Rear main replacement method.
« Reply #2 on: January 13, 2022, 08:05:09 AM »
As Johnny said, tug the motor.
87 V20 Standard Cab Longbed (current)

87 R30 3+3 Longbed (days of yore)

98 C2500 ext cab longbed

Offline 1987_Rabbit_Hole

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Re: Rear main replacement method.
« Reply #3 on: January 13, 2022, 08:39:48 AM »
Yeah I'm seriously leaning towards that method.  Plus, it'll give me an opportunity to clean it up a bit.  If it was a 2wd I might do it in the truck. 

Offline JohnnyPopper

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Re: Rear main replacement method.
« Reply #4 on: January 13, 2022, 01:08:38 PM »
Yes 2WD is a no brainer, but xfer case and tranny are brutal especially if you don't have a lift.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline VileZambonie

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Re: Rear main replacement method.
« Reply #5 on: January 13, 2022, 04:18:13 PM »
A) Be 100% positive it is the rear main.
B) Determine why it is leaking, make sure the PCV and breather are functioning correctly.
C) If the seal is crisp it probably wore a significant groove in the crankshaft so you may need to purchase a speedy sleeve kit.
D) If you are pulling the engine, that's the best time to reseal everything and give it a tune-up.
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline JohnnyPopper

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Re: Rear main replacement method.
« Reply #6 on: January 13, 2022, 08:22:45 PM »
Good stuff VZ,

I recently bought a seal for my timing chain.

The harmonic damper had a groove, but the seal was designed to be offset so I didn't need a speedy sleeve.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline 1987_Rabbit_Hole

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Re: Rear main replacement method.
« Reply #7 on: January 14, 2022, 06:35:41 AM »
A) Be 100% positive it is the rear main.
B) Determine why it is leaking, make sure the PCV and breather are functioning correctly.
C) If the seal is crisp it probably wore a significant groove in the crankshaft so you may need to purchase a speedy sleeve kit.
D) If you are pulling the engine, that's the best time to reseal everything and give it a tune-up.

Good advice.  Thanks.  Already done valve cover gaskets, pan gasket, and inspected around the distributor/intake area, and completely replaced the PCV system and verified flow.  I've eliminated all possibilities but the rear main, cam plug, and flywheel bolts.  All of those I've got to remove the trans or engine to see, so I'll know in a day or so. 

« Last Edit: January 14, 2022, 06:43:48 AM by 1987_Rabbit_Hole »