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Can I use big block stands with a 406 in my '68?

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clearance frame mounts
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#41 ·
In that picture it looks about 1/4" off. Loosen the mount to transmission bolts and see if you can line it up. May be even loosen the subframe to crossmember bolts,
 
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Discussion starter · #42 ·
#43 ·
Sorry, I thought it looked real close ! The engine and transmission are bolted to the subframe so loosening body to subframe bolts shouldn't help.

I have heard of another set of holes in the subframe for the transmission crossmember and I have heard of only the 2 of the 3 holes there. I would look to make sure you don't have more holes to move your crossmember forward. If a TH-400 crossmember had been used before, the farthest forward holes may be plugged with dirt and grease. This might make them hard to see !
 
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#45 ·
I just wanted to correct myself on the crossmember. Your original crossmember was for a 1969 Firebird. I believe this was the crossmember used in all '69 firebirds EXCEPT those with the TH-400. ( I had said it was for a TH-400 for some unknown reason) The transmissions mounting holes would be the same as the "4 speed" crossmember that you now have. The Firebird crossmember would be much weaker than that of the Camaro piece. I am not sure why they even bothered making this piece unless it was for cost savings.
 
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Discussion starter · #46 ·
Found out that the tranny is a supercase, which is adding 3/16" to the problem. That doesn't cover the whole fore/aft problem, but it accounts for a chunk of it. My bellhousing has a motor plate, I guess that might add a bit of length too.

The left/right is still concerning. The bellhousing is almost touching the tunnel, and the shifter rods are almost touching as well. Tried loosening ALL bolts a wiggle it into place, but that hardly generated any movement. Pulling the tranny towards the passenger side (for tunnel clearance) only makes the tranny mount bolt problem worse. The center bolt hole is almost aligned with the passenger side crossmember hole.

Is it possible that my crossmember was labeled incorrectly?

To be sure we're on the same page, the tranny mount is about 3/4" too far back, and 1/2" too much towards the passenger side. BUT, the bellhousing and shifting rods are hitting the tunnel.
 
#47 ·
No, I doubt your crossmember is wrong. If you measure it, you should have the same dimension to the center, between the two slots. A big block crossmember might work, but your engine will be sitting at an angle. It might work ok and it might vibrate like crazy. The output shaft of the transmission needs to be parallel with the input pinion shaft of the rear differential. I am going to guess that your shifter and clutch linkage are not 1st generation Camaro parts either. Hopefully someone else will chime in and tell you what you need for those pieces. I know a camaro clutch fork has to be used. If you take off the motor plate you can gain some more.
 
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#50 ·
Boucher421 said:
If I can pull the tail housing towards the passenger side to get some clearance from the tunnel, is it a bad plan to just drill some new holes (or widen existing) in the crossmember?
Click to expand...
If you want to just make it work, I would modify the tunnel. (dent etc.) Try to get those shafts parallel. (Trans and differential.

If you want it original, start with an OE transmission and linkage.

When 1 part is not OE it starts to snowball !
 
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Discussion starter · #51 ·
67_rcl - I have the hurst install kit for a 67-68 (3734529). The shifter is for a 68. A guy at hurst said I have the right shifter (vehicle specific) but the install kit is specific to the year of the tranny. Since mine has bolt on arms with tail housing #3857584, I figure its either a 69 or 70 tranny. Therefore, I need an install kit for a 69+. Maybe this will bring the rods away from the tunnel wall? Probably wishful thinking there.

There is a mounting plate -it's a solid piece that wraps around the bottom and drivers side. The shifter mounts to the plate. Also, I'm using the energy suspension tranny mount that comes with the 'must use' preload plate. Is this a 'must use' if I have the hurst mount plate there? I'd I don't need the extra plate, it'll drop everything down an 1/8th of an inch or so, possibly providing some bellhousing and rod clearance.?.?.?

Tjs- I'm about ready to dent, chop, cut, or drill. I see what you mean by snowballing with one non OE part. Even worse when you can't figure the specs on the part!

Here's all I know of my tranny:
Autogear supercase - #18-065-901-j (I can't find a decode for this)
Tailhousing - 3857584gm - 66-70 passenger speedo, 27 spline
Side cover - 3952648 - short boss bolt on type w/tcs on 3-4 (not sure what short boss refers to)
10 spline input
27 spline output
Not sure of input rings - I'd rather not pull it off to find out unless absolutely necessary.

Supercase adds 3/16". Sounds like post '71 trannies are 3/4" longer than earlier models. I read that casting #s shouldn't always be trusted. It'd be nice to have proof that its a later (longer) model. That would account for crossmember fore/aft issues. I could fix the left right issues with a hammer to the firewall, drill some extended holes in the crossmember, and move on with confidence that I'm not missing something that'll bite me n the @ss later!
 
#52 ·
Before you dent, chop, etc., is your subframe centered to the body? GM used 5/8 alinement pins. Try checking with a 5/8 bolt on the subframe mounting pad below the firewall.

That may solve the tranny against the tunnel trouble (hopefully), and you know the tranny is a little long, but it should still sit straight down the center of the subframe. I think in an earlier post you confirmed you have the correct frame stands, possible one is tweeked a little? Is it possible to loosen the frame stand bolts and pull the tranny over to line up with crossmember. Not sure how much adjustment that will give you, but it's worth a try.
 
Discussion starter · #53 ·
When just visually looking at the pins/bolts, it appears lined up. Both bolts lean outwards a bit. Is this normal, or should they be perfectly vertical?

Frame stands are good; I've triple checked and compared them to brand new ones. I have them loosened now and could (in theory) move the tranny over a bit, but the bell housing and rods are hitting before it lines up.
 
#54 ·
I know that you can slide the crossmember back and drill new holes in your sub-frame. People that have converted to a 700r-4 have done this. (see picture)

Image


The 69 Camaro's shifter was mounted on the transmission via a plate. Other aftermarket shifters were mounted to the transmission with a u-bolt. The 67-68 Camaro's had a plate that bolted to the crossmember and the transmission and your shifter bolted to this.

Image


Image
 
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Discussion starter · #56 ·
Saw in a muncie catalog that my side case (#3952648) is from a 70-74 muncie. The tail housing (3857584) shows from a 66-70.

http://autogear.net/ag_archive/pdfs/munciecat.pdf

Here's the words (cut and paste) i got from my buddy who I got the tranny from (for free! Awesome buddy!):

"Ignore the castings. My transmission was a 1968 or 1969 Muncie m21. First rebuild kept it an m21. Second rebuild bought m20 gears for "taller" 1st, 2nd, and 3rd gear ratios AND swapped in the supercase. That rebuild lengthened the tranny due to the supercase, but the install was transparent - everything lined up fine."

Hoping someone can pull some hidden nugget out of this. I'd love to find out that the tranny is a 71 or later model, which was 3/4" longer, then the supercase added another 3/16". That would clear up the majority of this issue.

Regarding the hurst install kit. Looks like I need to order a new part! Right now I have part #3734529:

http://www.hurst-shifters.com/wp-content/uploads/3734529.jpg

I'm hoping the new kit will bring the shifter forward a bit. Just to confirm, I have a 68 Camaro, but my tranny is a 70 or later. The install kit should therefore be for a muncie 452 (bolt on vs studs), which the hurst part number is 3737437.

http://www.hurst-shifters.com/wp-content/uploads/3737437.jpg

Thanks all for the help.
 
#58 ·
See post #5 in the linked thread below; Jody is a long term member here, and he should be easily able to help you sort out what happens when the aftermarket case gets thrown in mix. I'm sure the only reason he hasn't provided help here already is because thread is in engine and he monitors the transmission forum.

I'd have cut and pasted the contact info here but I'm on ipad now.

http://www.camaros.net/forums/showthread.php?t=216028

Make sure to let us know if Jody helps solve the problems.
 
Discussion starter · #60 ·
Thanks Jody. I'm still stuck trying to get the tranny mount lined up with the crossmember.

This won't solve the mount alignment issue, but do you happen to know which hurst install kit I should use? I have the shifter and kit for a '68. Most seem to think I need the install kit for a '69. I also read this will place my shifter further back, further aggravating my problem.

Also, does anyone know about how much my subframe should be able to move with the body bolts loosened up? I tried moving it left/right with some straps. Wondering if I'd be able to 'stretch' it a bit.
 
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TJS69
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