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How to: 2001 4 door 2wd rear main seal and oil pan gasket
Hopefully this is an appropriate place to post this(admin; please move if its not)
2001 blazer 2wd rear main seal and oil pan gasket replacment(pics at the end)
This is gonna be a long post but i Havent seen a good tutorial on this with all the facts start to finish, so i thought id document my experience with it. Initially i was just doing the rear main but my problem ended up being the oil pan gasket. So I did that as well as a new oil pump, and a billet pump drive shaft. FYI 4x4 blazer is a different animal, some of this will apply but there will be different steps for you 4x4 guys. I will say this took me 8 days(i worked most of them) however I did an oil pump, the oil pan, and a transmission fluid change in addition to it being my first go at this.
Heres the basic facts for those who dont want to read the long winded version
Label every bolt/etc you take out
An impact is your best friend for this job
It will take you a weekend(if you have a plan/all the needed parts) not a horrfic job but you better not be afraid to tear your truck down.
If you drop the transmission crossmember and drop the trans down, you can easily get at all the bellhousing bolts. No need to drill holes in the firewall or jack the body up
You dont need an alignment tool to do the rear main seal(only need what's included with the seal)
There seems to be 2 freeze plugs on the back of the motor, you may consider replacing those if they look bad.
You have to drop the exhaust, i couldn't maneuver it around it, just drop it, its not that hard just use pb blaster/heat and take your time.
As far as the oil pan goes....
Its a bear to do so give an extra day at least for it. On a 2wd you have to jack the motor up to get the pan off, it hits the oil pump pickup.
You have to remove the oil cooler lines, so at least replace the o ring where they meet the block.
And for those that want the full step by step with pics(its long so brace yourself)
Tools youll need
Transmission jack
Torque wrench
Lots of extensions/swivels
Work light
Basic hand tools
Impact wrench recommended
Floor jack
Some wood blocks
Also a set of picks and some stubby wrenches come in handy
Parts
New rear main seal
Some transmission fluid
Blue Locktite(torque converter bolts)
Muffler to y pipe exhaust gasket(if needed)
If doing oil pan,
Oil pan gasket
Rtv silicone
First disconnect the battery and place the parking brake.
Jack the truck up, make sure to do this evenly front and rear(youll thank me later)
Next remove the starter, just 2 bolts and 2 wires. Should take about 10 minutes to get off, tilt it forward, up then down and back, it comes right out. From there remove the plastic service cover secured with 2 10mm bolts. Now your looking right at the flexplate
Remove the belt from the engine, and rotate it by hand until you can see the first torque converter bolt. Then using various extensions and a 15mm, remove the bolt, rotate and repeat.you may have to wedge a screwdriver between the engine and flexplate if your bolts are very tight, there is 3 bolts in total. FYI dont turn the engine backwards, and don't skip this step. You may be able to remove the trans with out removing the torque converter but you can damage your transmission.
Now that those bolts are out go and mark how the driveshaft was oriented so you can put it back the same way.
Pull the Drive shaft.
At this point may as well unbolt the exhaust, undo the 3 bolts on each header, and the 2 where the y pipe meets the muffler. You can just let it hang down it leaves plenty of room. Might also be good to unplug those 02 sensors first.
Now go to the drivers side of the trans, theres 2 plugs on the shifter. Label and remove, from the factory theyre glued in. You may have to heat them to melt the glue. Either way take your time and just work em out. Pry the shifter cable from the linkage with a flathead, then get a 10mm wrench under the secondary cable bracket at the back, remove it and set the whole shifter cable out of the way.
Go ahead and unplug the VSS, on the passenger side on the back of the trans.
Its easier to wait to remove the main trans harness, cooler lines and dipstick.
Now unbolt the 6 crossmember bolts, and the 1 center bolt for the transmission mount. Slide the jack under your trans, remove the crossmember, a rubber malet is helpful for this step.
Now lower the jack a little bit at a time, if you go to far your trans will puke fluid out the tailshaft, and you could crush your dizzy cap on the firewall.
At this point when its lowered enough you can see all 9 bellhousing bolts, use a box to mark where they came from. Remove the top 5 bolts(theres not one in the top middle)
Now remove the main harness plug on the passenger side, it has 2 tabs at the bottom you squeeze with your fingers, it comes right out. Then pull back the plastic covers on the cooling lines and using a pick remove the QD clips and pull the lines out. Pullout the dipstick from the engine bay. At this point the trans will be leaking some fluid so be ready for it.
Finally Remove the bottom bellhousing bolts and seperate the engine from the trans, don't force it will come easily. Manuever it around and pull it back
Now that the easy parts done, lets get that flexplate off. First mark the orientation of the flexplate. Then undo the 6 bolts holding it on. Mine were a bear to get. I had to put vise grips on the flexplate and use a breaker bar to get them off.
i wouldnt recommend it, but At this point if youre just doing the rear main you can possibly just pluck the seal with a pick and drive in the new one, however the seal is mostly metal and is much easier to drive out from the rear of the cover than the front. If you make it work then just put her back together(i have simply heard this, havent tried it but looks like it might be possible)
However if your the adventurous type, or if its your luck that the pans leaking not the rear main. Go ahead and undo the 2 thru bolts for the motor mounts and buckle up for knuckle busting fun.
Wipe off all the dirt and grease on and around your motor(dont want it in the oil pan)
Remove the oil cooler lines(you may have to do this with the motor jacked up)
There's a strap holding the transmission cooler lines to the oil pan, 1 10mm nut, remove it and pull the lines aside.
Next place a block of wood under the oil pan and jack up the motor, you can also put a jack on the front to make this easier(pick a solid point to lift from), once its positioned to your liking wedge wood blocks between the engine and frame. Bring the jacks down, dont worry its not gonna fall on ya.... If you did it right.(FYI removing the top fan shroud gives more room to lift the motor)
Now remove the bolts securing the rear main cover, then remove all the oil pan bolts(mark where they came from).you can get at all the pan bolts with a ratchet with a swivel no need to do anything crazy here. At this point slide the pan down and remove the rear main cover. Hopefully you drained the oil before you dropped the pan....
Maneuver the oil pan off, this is more an art than a science.
Marvel at the fact your whole blazer is apart
Now go ahead and cover your bottom end with a trash bag to protect it, i personally sandblasted and painted my oil pan, That's up to you, However I would at least clean it while its off.
At this point go ahead and clean the gasket surfaces of the block and oil pan. Use a scraper then a rag with brake cleaner.
Give your bottom end a good inspection while your there. You may consider repacing your oil pump while your here, or at least the pump drive shaft that has a plastic coupler. The billet steel shaft is like $20. I somewhat easily broke the plastic coupler removing my old pump shaft. Be aware if you mess with the oil pump you need to prime the oiling system, tools like $10 or do what i did and use a modified old distributor to prime it.
If you choose to install a new oil pump. Heres the basics. The pickup tube is very tight, you may consider getting a new one but the old one can be reused if you can get it off, You have to set the pickup depth(depth from oil pan) correctly should be around 3/8 inch. Make sure to torque the oil pump to 66ft lbs. And most important, YOU MUST PRIME THE NEW PUMP. Or your engine will start with no oil pressure and take a minute to build it up. But all in all pretty easy to change.
Install the new rear main seal and cover gasket on the rear main cover. I used a squeeze clamp with rubber jaws and finished with a wood block and a mallet. place this on the motor(install the rear main seal dry, per felpro instructions) this doesnt require an alignemnt tool as theres studs to line up the rear main cover. As you Slide it on, use the included installer tool(white plastic thing) just slide the seal on the crank and it will push out and fall off as it goes on, it keeps the edge of the seal from folding up, nothing more. Might take several trys, you will know when you get it.
Now install the new gasket on the pan, it has grooves to sit in so its not too bad, apply a little rtv at the corners, and carefully put the pan back on. Install all the bolts and torque to spec. This requires a lot of maneuvering to get it on right.
Torque all the rear main cover bolts to spec
Go ahead and reinstall the oil cooler lines with the motor still jacked up, inspect them for damage first, much easier to replace now then later.
BEFORE YOU GO ANY FURTHER, CHECK THE TORQUE CONVERTER BOLTS TO MAKE SURE THEY THREAD INTO THE CONVERTER SMOOTHLY AND THE THREADS ARENT DAMAGED. I realized this after i put mine together and had to get crafty to get the converter to the motor with out dropping the trans back out.
Jack the motor back up, carefully remove the blocks and let it back down. At this point put back together everything you took apart(take your time, torque everything to spec) add a lil trans fluid, fill her up with oil and pray you did everything right. Hope this helps answer some of yalls questions on this job and clears up some confusion about what is and what isnt possible when doing this.
FYI when you put the trans dipstick back in, do it from the engine bay and tap it with a rubber mallet to drive it back in. Clear view of the flexplate and bolts Mark the driveshaft and the yolk so they go in the same way they came out Heres the shifter setup with the 2 plugs Sorry for the poor pics, but you can see the bellhousing bolts from here with the trans let down These are the tabs you squeeze in on the main harness plug, 1 on each side. A pick works good for removing these clips, they must be undone to remove the trans. Once the clips are out they pull right out You will need lots of extensions to reach the bellhousing bolts Once its all off let your trans down and slide it back. Heres how i got my flexplate bolts off, be careful not to damage the flexplate Heres what the rear main cover looks like, and now im thinking that might be the back of the cam and not a freeze plug but dont know for certain, if anybody does would appreciate the wisdom. If you do the oil pan go ahead and check your rod slop, cylinder walls, etc while your here. Heres why you may consider replacing the oil pump driver, those 4 broken pieces were the plastic coupler.... As you can see the pan gasket has nice grooves to sit in, makes install a little easier.
Pry the shifter cable off with a flathead screwdriver. It just pops on and off The shifter linkage can be folded back once you get it off You can squeeze a 10mm in here to get at these 2 bolts, this is easier than getting the cable out of the bracket
Last edited by Blazin_Alexei; Jun 23, 2019 at 06:57 PM.
Reason: Typo
If you drop the transmission crossmember and drop the trans down, you can easily get at all the bellhousing bolts. No need to drill holes in the firewall or jack the body up
Excellent write up! GJ!
Been there done that. I was doing the job with a ride on the garage ground (no hoist) and I had difficulties reaching the bolts of the crossmember on one side. Additionally I found difficult to support the transmission, so lifting the body was easier to do, and at the end, I left it 2" lifted, just fabricated the polyurethane pads.
I've been actually swapping the engines that time, and what I remember, the bolt threads were messed up. One was somewhat metric, while the other one was imperial.
Not sure if there's an access to replace the sort of a "liner" connecting the pump to an intermediate pump shaft, but I'd suggest to replace it, if You're already there. That was my primary reason to swap the engines.... EDIT: LOL OK, I've read it once over again and that is "those 4 broken pieces were the plastic coupler." I am referring to.
Last edited by Mike.308; Jun 25, 2019 at 05:20 PM.
How to: 2001 4 door 2wd rear main seal and oil pan gasket
