Rear main vs tranny input seal leak

[Texasdoc]

I have an increasing amount of oil dripping from my engine plate. T5z mated to 408w. At first I suspected the rear main seal. I tore everything on the back of the motor apart. Tranny off, clutch off, flywheel off, then oil pan, 5th main cap, and then replaced rear main seal.

I examined the flywheel and clutch, no oil on them that I could see. Oil plugs on the back wall are dry. Nothing dripping down from the intake. Heads and valve covers are dry. I did notice that the inside of the bell housing was wet with oil - but it didn't register at the time.

I reassembled everything but still have the same leak - from the engine plate. I'm now thinking that it may have been the tranny the whole time. Any suggested way to test the tranny input shaft seal, or just rip it out and replace it anyway?

I will someday get a TKO600 for this car. I just had a dyno session tuning the EFI. 407hp, 489tq at the wheels. I know this T5 cannot handle that much power. Since I never abuse the tranny, I was hoping to delay that for a little. My other vacuum (Jeep) has gotten lots of new parts lately. The spousal unit is starting to glare at me with those eyes....

[Cashburn]

789tq ???

[Texasdoc]

Oops. Typo. Edited in original post....

[DanEC]

Usually lube from the idler shaft in the transmission doesn't make it's way into the bellhousing - it will run down the outside of the bellhousing to the low point on the transmission and/or bellhousing. If the rear of the engine and front of the flywheel looked dry then that pretty much just leaves the main input shaft seal on the T5. That would be a little unusual for most of the old 4 speeds but maybe not for a T5. I would think it might eventually contaminate the clutch too.

[Detroit Bill]

You can get fluorescent dye and put it in the trans then view the leaking area with a black light. It will look like a murder scene but you will be able to know if it is the trans and see its Origin.

[vref120]

Flywheel bolts?

[Gaz64]

What oil is in the engine, and what oil is in the transmission?

If it is the input shaft seal, oil residue will be sprayed around within the bellhousing.

Surprised the trans is still intact.

[Wbulk]

The T-5 oil should be red Dextron II or III. vref120 is right, if it's engine oil the flywheel bolts require sealant on the threads. They go right to the oil pressure side of the crank on the SBF. If you replaced the rear main seal did you put silicone between the main cap and the seal. You can't do the silicone on upper with the engine in.

[Texasdoc]

The flywheel bolts were all sealed. The main cap was also sealed. So was the ends of the rear main seal halves.

Originally Posted by Gaz64

Surprised the trans is still intact.

It isn't.

The engine has Catrol 10W30 dino oil.
The tranny Valvoline MTF. Actually, most of the MTF is now inside the bellhousing and/or a puddle on the floor.

I didn't realize I was making that much power. I thought I was closer to 350/400. Assuming 20% drivetrain loss, that's 500hp/600tq. The T5z is only rated at 330.

So now I'm looking at a TKO600, Mcleod RST dual clutch, quicktime bellhousing setup. What's another $4k?

[vref120]

I had a 408W in my car with the 6, qucki time and Ram clutch. Was a very good combo until the RMS leaked and coated everything badly. I reset and replaced the 408 with a 427 dart but still have the same setup for the tranny. You will like it!!!

[Texasdoc]

Yep, it was the T5. Clutch and flywheel look dry.

Youtube Link

[Gaz64]

A lot of rear wheel drive transmissions will have input shaft "wiggle" like that, it's simply a little movement in the input shaft bearing, being a single ball race.
The seal is just outboard of the bearing. The spigot bearing supports the front of the input shaft.

Was there any trans fluid from within the throwout bearing guide on the front of the trans?

[RICK LAKE]

Texasdoc Tom you are right about the amount of torque that your trans can handle. The other thing is was the bellhousing centered on the block and checked for out of round? What bellhousing are you using? I hope it's an aftermarket one. Quicktime, Lakewood,( the worst for being off center) for even the stock setup needs to be checked. After this is done, you need a new front bearing and seal for the input if you stay with the T5 trans.
I am not a big fan of these trannies and would tell you to lok at the Richmond super street 5 speed trans with OD. The design is stronger, bolts right in and can use the orignial looking shifter and handle in the car. May have to center it on the tunnel or even relocate. This trans cost more but has only 2 main shafts and not 3 or 4 to supply power to and wear out with abusive driving. I ran a 6spd richmond for 7 years without a problem after junking the centerforce clutch. This trans has a 450/450 rating but is 1" longer in the mounting location and 1st gear is not used. Find a trans with a 2.80 or less first gear. Because of the power and weight of the car, you don't need anything higher unless you are plowing a field or pulling out stumps.I swapped to a G-Force 5 spd because of racing and hard abuse. Also uped the power to 500/600 and the 6spd would handle it but not the abuse level.
Take the nose off the trans and get a new bearing input housing, bearing and seal if it don't come complete and swap over. This will get you running again.Drive easy and enjoy. Rick L.

[Texasdoc]

I just had the stock aluminum housing. I'm going to a QuickTime housing with this swap. I will center it with a dial.

[Texasdoc]

Now I'm not so sure.

Gaz64 says the input shaft wiggle is normal. The inside of the bellhousing is wet with oil. There is also a black grainy substance everywhere. Not sure if this is just dirt that got in thru the clutch fork opening, spent clutch material, or something that came out of the motor or transmission. What is this black stuff?

I tried to remove the throwout bearing sleeve, but couldn't get it to budge. I took off the four screws that appeared to be holding it in place, but it still wouldn't release. I attempted to pry it with very light pressure - still not coming off. I didn't want to force it.

When I went to drain the transmission, it seemed full of fluid and the oil looked clean. None of the black grainy stuff noted in the bellhousing. Earlier when I said the clutch and flywheel looked dry - that was before I removed them. Took the clutch pressure plate off today. Clutch disk is dry. Front of the flywheel is dry.

Next I took off the flywheel. The engine side of the flywheel has a little oil. The engine side of the engine plate is wet with oil. The back of the motor wall is minimally wet with oil. The back of the crank and back of #5 main cap also lightly 'misted' with oil. The 'freeze plug' looking thing behind the cam was a little wet too. Nothing obvious anywhere but it all was 'misted' with oil.

So I cleaned everything on the back of the motor with a shop rag. Turned the motor to TDC, and removed the distributor. Next, I ran the oil pump with a driver. I didn't see anything leaking. I ran it for quite a while - so much it burned up my drill. Not a single drop (or hint of a drop) of oil anywhere visible on the back of the motor. Even though the flywheel bolts were on the floor, there was no oil coming out. I tried to blow into each of the holes and no air would go in. I stuck a small screwdriver into the holes and it didn't go more than 1 inch into the crank. This is a SCAT crank so I'm thinking their flywheel bolt holes are blind and don't go into the oil system.

I first noted this leak shortly after I installed the new motor - 408w. I had a 351w initially. I didn't have any leak then. Before the recent dyno tuning, every time I would drive it, I would get a small drip that would come off the engine plate. Last month I took everything off, replaced the RMS, was very careful about sealing the main cap and oil pan. That did nothing. Immediately I noticed it was still leaking. Still a small puddle - same size as before. About 1/2 tsp I would guess. Diameter of the puddle on the floor was about 2 inches. After the dyno session, the puddle has grown to about 12 inches across. It also has a black appearance. Before the dyno it looked like clear oil. Now its dirty black.

What next? I am definately going to replace the tranny. It won't last behind the motor anyway. Do the symptoms sound more like the RMS or the tranny? Should I put the flywheel back on and run the motor without the clutch and transmission to see if that makes it leak? Is it ok to do that?

[Jac Mac]

Flywheel bolts on 351w based 3" main cranks don't usually go thru to oil in pan as they are blind.
With regard to the RMS did you install the seal halves with ends staggered in relation to cap face , eg 1 up, 1 down, by about 1/4" to ensure seal ends are correctly lined up?
Grimey stuff could be clutch lining material mixed with oil.

[Texasdoc]

Yes, I offset the edges and applied a small drop of RTV to the ends. I plugged hole Y.

If it were the RMS, wouldn't it show signs of leaking when the oil pump was driven?

[Gaz64]

Not sure on Windsor but Cleveland 351 cranks are known for the crank rear flange to become 6 sided from the flywheel bolts flexing under heavy load.

A mate of mine found this out the hard way, similar to yours.

The rear main seal cannot stay on the crank if it is not round.

[Jac Mac]

Originally Posted by Texasdoc

Yes, I offset the edges and applied a small drop of RTV to the ends. I plugged hole Y.

If it were the RMS, wouldn't it show signs of leaking when the oil pump was driven?

No, the oil drainback in the rear main cap is approx. 0.75" x 0.15" so the small amount of oil escaping from rear side of the #5 main bearing which is supplied by a ~0.300" dia gallery is not likely to build up pressure. Very rare, but occasionally I have found that drain hole has not been created due to casting faults.

Gaz 64's comment might have some merit as 351c & 351w share same rear seal dimensions, more likely if flywheel bolts have been over-torqued (85 ft/lb). One possibility in regard to this is if someone has used shorter flexplate bolts with a flywheel, lower number of threads engaged in crank with that combo will result in crank flange deformation or thread damage.

[Texasdoc]

The crank, flywheel, and ARP flywheel bolts are all new- less than 200 miles. I torqued them to 85 ft/lb. Never over.