Napoleon1991

I have a 403 in my 69 cutlass with a th350 and have been wanting to swap in a 4 speed. My biggest problem is that im not sure if the crank is drilled for the pilot bushing or not. I know that 403s never came with 4 speeds behind them, but I have heard some people say that all 403 cranks came drilled from the factory. The engine has been rebuilt so there is a chance the guy who built it had the crank drilled, but I have no way of finding this out. I did notice that the block has the threaded hole for the zbar stud which I thought was interesting. I know the only way to find out for sure is to drop the trans and look, but I was hoping someone out there could tell me weather or not the 403 cranks were drilled from the factory. Thanks.

Napoleon1991

Anyone?

2blu442

I've only had one 403 engine, and it wasn't drilled.

Napoleon1991

Thanks for the reply. Ive heard about the adapter pilot bearing for auto cranks but it seems pretty cheap and gets negative reviews from everyone whos used it. Is there any other bushing / bearing that would work, or is pulling the crank and having it machined for the correct bearing my only option?

64Rocket

I have 3 403's and all have a drilled crank.
To me it is a very easy conversion. I hand drill the crank a little bigger than the snout of the trans and use the pilot adapter. No problems.

Gene

Octania

All the 403 cranks I have seen are drilled deep and with 3 diameters.

HOWEVER, there is no guarantee that these diameters are just right for a GM factory pilot bushing or bearing. All we KNOW is that the largest one is correct for the protrusion of the std issue auto trans converter.

The clearance for the trans shaft does appear to be there. Worst case, I would think, one would need to have a bushing machined from brass that fits the crank's 2nd hole and the trans's pilot tip. Have 20 made and sell the rest, becoming rich as the kingpin of pilot bushings that fit right...

64Rocket

If you buy the bearing,
http://www.rockauto.com/catalog/more...914&cc=1213489
or you can buy the bushing,
http://www.rockauto.com/catalog/more...286&cc=1213489

Your choice.
Gene

Napoleon1991

Thanks for the links. Are those the normal pilot bearings/bushings, or are those the conversion ones?

64Rocket

Those are the normal replacement brg/bushing
The adapter one is a little bigger
A couple of the Olds bender has the adapter one
Gene

Napoleon1991

Ive done a little research on the adapter bearings that mondello and supercarsunlimited sell and it seems that many of the people who have used them, have had them fail shortly after installing them. I was told there are a couple of bushings that can be used as an alternative to convert the auto crank.

They are McLeod #8617 and Dorman 690-035. These do look a bit stronger than the mondello converison bearing. Would either of these work in the event that I find out my crank isnt drilled?

83-425

is there any one of you 403 guys know what the factory cam specs on a 78-79 403 ?? in am doing a factory rebuild .thanks

jackolds403

Hello, some news about pilot bearing solutions?
I'm a new olds 403 owner on a trans am, and the goal is install a muncie 4speed: seem hard...

mjrj

About 10+ years ago I put a tremec TKO behind a 403. Used a pilot bushing that had been machined down to 1.310" to fit in the crankshaft. I've only driven the car 200 miles since, seems to be working fine. I do have a rear main seal leak that I may pull the engine to repair so I'll see how its held up.

nedlancaster

There is hope out there! There is a bearing designed to go in the crankshaft hole to install a manual trans. into an automatic crankshaft. I purchased one several years ago from The Parts Place 217 Paul St Elburn, IL 60119. Bearing Assy No. 12-455. You may have to shorten the input shaft by .250-.375 of an inch but that's not a big issue. Hope you have success.

jackolds403

I hope no one surprise, i think to take the bearing from Mondello or Dick Miller, already machined for the small hole of the 403 crankshaft...

jackolds403

I've spent my last weeks to study about the T5 wc and nwc for the swap on my 403. Really i'm going away with the doubt about his resistance under the 403 torque.
Jeff from Transamcreation tell me is a very bad choice put a T5 behind a 403, because the trans can't resist enough under the torque:



"Hello,
The T5 was used on Camaro Firebird starting in '83 on a 305. In '84 there was a 305 H.O. with T5...they had breakage with that. When the 305 TPI came out, the T5 wasn't strong enough for that. GM redesigned the T5 (World Class) in late '87 and then started offering with a 305 TPI, but never with a 350.

It can barely handle the torque of a 305.

You can by a G-Force rotating assembly for around $1650 to install in a stock case and then you would be OK. But you still have so many other obstacles that will put you at more money than an aftermarket Tremec 5 or 6 speed.
The Muncie will hold up fine. The only issue being what you are going to do with the rear end ratio.
Assuming you have ’77-’79 Trans Am with 403, the stock rear end ratio is 2.73.
A stock ’79 Trans Am with 400 and Super T10 has a 2.64 first gear and 3.23 rear ratio. Which give you a 8.53 total overall first gear.



If you have an M20 (2.52 or 2.56 1st gear) with a 2.73 rear ratio you have a 6.87/6.99 overall 1st gear….that will be pretty tough on the clutch. If you have an M21/M22 (2.20 1st gear) and 2.73 you would have a 6.01 overall 1st gear…you WILL burn up the clutch with that, no question about it.
Going to a higher rear end ratio will help, but then you’re up in the RPM So you want to check what you have before you do it.Probably the easiest way to explain would be if you took a regular manual transmission car and started off is 2nd gear every time. You would burn up the clutch.



Like I mentioned, the solution is changing the rear end gears to 3.42 or 3.73. It would driver good, but at 60 mph you would be close to 3000 rpm.



The M21 was built for straight line performance, not highway cruising. So if you don’t drive on the highway, it will work good, just change to a 3.73 rear gear.



A Tremec TKO 500 has 3.27, 1.98, 1.34, 1.00, 0.68 ratios.



So a 3.27 1st gear and 2.73 would give you a 8.92 overall 1st gear which would be perfect. And with 5th gear being .68, you would be much lower at highway rpms that what you have now.



And then changing to a 3.42 ratio rear gear would balance the car perfectly. It would be a lot faster off the line AND 15% lower cruising rpm on highway."


Ok, i cant spend 8.000$ to have a TKO 5 speed in Italy, so i decide to install the muncie 4speed (i bought for 2500$ with lakewood scattershield, clutch pedals, 2 type of shifter box, linkage, extc) , and change the gear on the differential as the Jeff suggestion....

Thank you Paul!

Kennybill

Question to the thread starter, Napoleon 1991. Did you put a Muncie behind your 403? If so which pilot bearing adapter and how did it work out? Inquiring minds want to know. Thanks, Ken

BangScreech4-4-2

Napoleon 1991 hasn't been seen in these parts for over a year.

Kennybill

His profile says he was on September 16, 2018.

BangScreech4-4-2

Pardon me, I should have said he hasn't posted in over a year.

brownbomber77

Draggin this up from the dead. I have a 403, LOOKS like it was drilled for a pilot, but the factory one for that year won't work. ID of the second hole where the bushing would go is 1.355". Factory is 1.381. Thought about just cutting it down on the lathe but wanted to ask here if there was an alternate solution.