engine and drivetrain 5-speed swap woes...

[pcassidy]

I have a 1973 that used to be an automatic, and a previous owner turned it into a manual... but, unfortunately, a 4-speed.

I've only driven it a couple of times, and the last time, on the highway, the driveline shudder was so bad that I kept my hand on the shifter to settle it down. Either a flex disk or a center support bearing was ready for replacement... or both. I found that the flex disk had horrible splitting.

I figured that, as long as I was tearing into that area and there was a 5-speed with 125k miles available locally, I should do the swap. I intended to do it someday, anyway.

Where I am at right now? When the engine is at rest, as dictated by the motor mounts, the transmission sits within 1/16" from the stock driver's-side cross member tab. This is consistent with the oldest how-to posted about the swap. It mentions that the motor mounts will push the tranny/engine to the driver's side.

Where this becomes a problem is with the alignment to the center support bearing. For the sake of locating, I made a precision shaft to slip on the output shaft of the tranny, and it shows the the tranny needs to move more to the driver's side to be aligned with the center support bearing. I can cut the stock, driver's side tranny cross member mount to accomplish this, but the tranny is going to end up right against the tunnel wall... and the brake line. Sure, I can move the brake line, but what about the tunnel wall???

Another issue is how the tranny lines up vertically with the center support bearing. When I slip the support bearing assembly over the precision shaft I made, it shows that the transmission needs to go up. I shim it up until it is against the top of the tunnel, and the support bearing is still nearly 1/2" below the center support bearing mount tabs. I suppose I could space the support bearing down. But, I would like to know why this is not working out!

I have checked the motor mounts to make sure they weren't broken and causing the engine to sit in a funny position. I have not tried to see if I can loosen them and move the engine around then lock the engine down in a better location.

Is the transmission tunnel for an automatic different than the tunnel for a manual? One indicator that this is possible is that the how-to says the tunnel will need to be cleared for the clutch slave cylinder to have clearance. My clutch slave cylinder has tons of room without modifying the tunnel. It seems crazy to not make the tunnel one-size-fits-all, as it would be much more economical to manufacture. But, something is amiss.

Anybody have any ideas?

[Guest Anonymous]

Tunnels on the automatics were larger than the 4 speed models so fitment should be easier side to side.

[pcassidy]

That would explain the extra clearance at the front of the tunnel, but it does seem to be worse than it should be once the tunnel gets narrow.

[Kidasters]

by C.D.iesel that showed how you have to "modify" the tunnel with a BFH (that's Big Friggin' Hammer) in order to get the clearance you want.

I can't find him.

E-mail him through the board. Maybe he'll repost.

Creighton - HELP!

Ken

[pcassidy]

There is mention of modifying the tunnel for the clutch slave cylinder to have at least 1/2" clearance, but mine has plenty of room without the hammering. Now I understand that it is because the car started life as an automatic. Unfortunately, that is not helping me deeper in the tunnel.

I could just move the tranny to center of the tunnel and re-mount the center support bearing tabs to put the center support bearing in line.

My thinking through this is to protect the flex disk by keeping the front section of the drive shaft aligned between the tranny and the support bearing. Maybe it is all taken up by the u-joint on the front half, but it seems foolish to not try and get it aligned as good as possible... let the rear section of the drive shaft work the u-joints, because it has more joints and no flex disk.

[aa/fd]

I can add that my 5 speed was very tight to the top of the tunnel compressed the foam around the shifter mount snugly, your correct about the alignment between the output of the trans and the center bearing. I used a long straight edge and tried to align the whole deal pinion to crank flange. I then tried another approach, one of those laser pointers fastened to the output shaft center pointing at the pinion. It actually worked quite good for this and plus they render "photo cop" cameras very myopic with repeated exposure. My engine mounts turned out to be the biggest offenders.

[BarryA]

no reason why everything shouldn't line up (as long as all the mounts, etc, are in good shape) - automatic trans tunnels are significantly bigger than those in manual trans cars, but everything else is the same (front cross member, engine mount locations, driveshaft center support location, rear suspension cross member, etc).

I'd consider replacing the front motor mounts and checking the mount brackets (especially the driver's side) - if the brackets are solid and the motor mounts are replaced the engine should be properly located, and you can proceed to figuring out what else is going on.

Assuming the driveshaft center support is intact, the critical factor is the alignment between the output flange on the trans, the guibo, and the input flange on the driveshaft - with everything else bolted up solid, a new quibo installed and the nuts on the guibo bolts backed off a few turns, any gap between the driveshaft flange and guibo should not change at all as the driveshaft is rotated by hand. If the gap is different from one flange to the next, it indicates misalignment between the trans and driveshaft..........

[M3M3]

i just put a 5spd in my 75 and have this exact same problem. tranny jammed all the way to the left and up against the top of tunnel hard (needed stack of washers under tranny bushing). the side to side alignment at the guibo is ok, but the up/down alignment requires almost 1/2 inch of washers to lower the center bearing. now the quibo is aligned correctly, but the center of the drive shaft is lower than the ends.

it really looks like the engine is mounted too HIGH. if engine was lower, the angle would be better. i have new poly engine mounts from IE. they are the exact same height as stock bushings, but since they are eurathane, maybe they don't compress a "normal" amount to lower the engine? if so, seems like the poly mounts should be manufactured shorter than stock.

anyone make shorter engine mounts?

[pcassidy]

Has ANYONE ever done a five-speed swap on a former automatic? I am still having trouble, and the only way I can see to get the transmission lined up with the center support bearing is to shift the whole engine more than an inch towards the passenger side.

I have that alignment shaft which I made on the transmission, and it extends out to the center support bearing area.

I center the transmission in between the transmission cross member mounts and shim it so it stays centered.

I remove the motor mounts and push the engine over towards the passenger side until my alignment shaft is centered horizontally in the center support bearing.

I am now over an inch out of position with the motor mounts.

I feel that the 4-speed must have been misaligned, so that is a bad situation to fall back on. I am not going to put in an automatic! The only choice is to move forward with the 5-speed, and that means a custom motor mount system.

Before I do something that extreme, I'd like to hear from someone who has done a 5-speed or even a 4-speed in a former automatic, and can tell me that they don't eat flex disks.