how do i replace a rear main seal on my 305 tbi automatic 1989 firbeird formula.alos do i have to unbolt the crank to get to the seal.

 

You have to remove the trans, clutch/torque convertor, and flywheel to replace the RMS on that engine. All you need are the sockets for removing the various bolts and a flathead screwdriver to pry the RMS out of its housing with, since most SBC's after 1986 are equipped with a one-piece RMS. Once the flywheel is off, removing the seal is easy as pie... just pry the old one out, lube the new one, and install it.

 

yep.. and use a bit of common sense.. try not to scratch the sealing surface of the crankshaft, or it'll chew the new seal up pretty quick... though, they can be a pain trying to remove gently.

 

It is usually easier if remover the oil pan too. Granted, you will have to get a new seal for that too, but it never hurts.

 

i can't think of any reason why you'd want to remove the oil pan or why it'd be easier on a one piece block

 

im doing a cam swap anyways also as the same time as the rms so i figured mine as well get all new seals alos what do you recomond for brand of gaskets.

for rear main seal and oil pan gasket id rather pay alot for a really good gasket then a couple dollars for a pos gasket.any recomendations.i was thinking fel-pro.

 

oh yeah and im changing the heads so whats a good head gasket for a 305 tbi and the comperssion is going to go up so i dont want the factory gaskets.

 

I know this kinda off topic but I know the rear on my old 3.1 should the same right? And how hard is the front seal? I just dropped the tranny out the other night after work. I getting tranny rebuilt for 300+ hard parts.

 

For the 3.1, it has a similar RMS in that it is also a one piece. However, to change the front seal, you have to drain the oil and coolant, move/remove the power steering pump and AC compressor, and the water pump has to be removed to get the timing cover off. Good time to throw in a timing set too.... Anyways.. you also need to pull the oil pan or just the front of it (so I've heard) so that the timing cover will seal properly.

I believe it may be possible to replace the FMS without removing the timing cover, but it is best to remove it since you probably need a timing set anyways if you are doing this....

Also forgot you need to have a balancer puller on hand to pull that off as well.

 

Thank so much for the info. I've asked the techs at my shop about it but they they said they havent done many v6 f-bodies. Since Ive been there i see mostly camrys and hondas getting hardcore stuff. Rear mains rairly timing belts/pulleys all the time.
But i watched i guy put front main on a lt1 in caprice and tool is there i just ask my mechanic friend to use it.
THanks again though maverick

 

Forgot to mention that you should check the balancer for a deep groove worn into it by the timing cover. There are repair kits available. However, if the balancer has a bad rubber sleeve between the two halves, throwing off the timing, you need a new one.

 

you don; thave to take the engine out to change it do you ?

 

Not really. Even if you have a V8 with a two-piece seal it is possible to do it in place. Although it is easier with the engine out because it is easier to get at, it can be done in the car.

 

After reading this I noticed something that may have been misunderstood.

You do not have to drop the oil pan on a one piece rear main seal block to change the seal. All you have to do is what Maverick described (and very well I might add).

Don't take that wrong. If the oil pan gasket is leaking replace it as well. I'd recommend pulling the engine though. The crossmember in our cars makes dropping the pan a real PITA.

 

Thanks for the compliment. AJ. I had to research this as I have to do it myself with my 2.8 V6...

 

Just remember the rule...

Count backwards from 10, 9, 8, 7, etc.

You'll need it.

 

for oil pan gaskets you can't beat the 1 piece gasket. only one i've used is made by fel pro, about the only gaskets i use are made by fel pro.

 

Yeah, the one piece rubber pan gaskets are niiiiiiiiiiiiiice

 

The engine has to come out anyways .. So I get to do it the slightly easier way...

 

86 and newer crank and block and pan were changed for new one piece RMS design, fronts stayed the same 55-up

to do front one youll need a balacer/pulley puller/installer tool, inexpensive for what it does for you at local parts stores, try to get a good name one, and do get grade 8 bolts isntead of using what comes in the kit with puller, this same tool will also pull steerign wheels too
the bolts you need to pull a steering wheel are two 5/16" x 16TPS bolts about 6" long

need three 3/8" x fine thread bolts for chevy dampner/balancer

 

Is it the same in V6 3.1 motor?

 

12 years later..............

 

Done 2 3.1s so I'd like to think it's the same... Only different V6 is the earlier 2.8 with the 2 piece RMS...

 

Well it's almost another year from the last post on this, but I suppose it's better than opening a new thread.

I'm about to attempt to do this with the motor in the car and wanted to confirm.

I've got a 400SBC in my 85 TransAM, so it's a 2pc rms that's leaking like crazy because when the seal was installed it was :
1) put in flush with the caps &
2) With a dab of rtv sealant on the joins

I have a 4L60E 1 piece attached and from what I've read, if I jack up the motor, pull the mount bolts and put a couple of pieces of wood between the mounts and cross member, I can remove the pan without taking off the transmission, and can then get to the RMS and replace without pulling the motor or dropping the crank.

Is that correct?

When I jack the motor, do I need to undo the trans cross member as well to allow it to angle with the motor?

I got the rubber 1pc felpro sump gasket too, even came with a nice set of bolts.