Author Topic: Position of 4-speed trans hump?  (Read 3719 times)

Ryoko

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Position of 4-speed trans hump?
« on: January 31, 2018, 06:20:56 PM »
I'm getting ready to cut and weld the trans hump as part of an auto to 4-speed conversion. The hump was removed from an 81 4-speed, but it was installed very sloppily  by the factory. So the measurements are in doubt. I think the spacing should be 10-7/8" as measured in the picture from the console mount to the edge of the flange on the hump panel. Could someone confirm this? (The newspaper is there to make it easier to see since the floor is black.)


cyber104

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Re: Position of 4-speed trans hump?
« Reply #1 on: February 01, 2018, 06:44:50 AM »
I would be glad to help you if I can.  However, my car currently has the full interior including carpet in place.

Am I able to take this measurement for you with the interior in this state or would the car need to be stripped inside?

Chris
1978 TA 4-Speed W72

Ryoko

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Re: Position of 4-speed trans hump?
« Reply #2 on: February 01, 2018, 08:40:54 AM »
Probably not. The measuring points are hidden underneath the carpet and center console. But thanks anyway.

I'm pretty sure it's where it needs to be. I just wanted to double check.

Ryoko

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Re: Position of 4-speed trans hump?
« Reply #3 on: February 01, 2018, 11:12:26 AM »
I dug out the old center console and placed the shifter tunnel back into it. It looks like the hump needs to go 1/4" forward. This brings it close to where it was when it was in the '81 (despite the poor installation).

Casey

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Re: Position of 4-speed trans hump?
« Reply #4 on: February 01, 2018, 05:18:24 PM »
From my understanding the 4-speeds weren't the cleanest install from the factory, since so few had them the body was set up for an automatic and any 4-speeds the shifter hole was cut out with a torch and then they tack welded the shifter surround panel into place.  Job done.  At least that's what I've heard anyway, so the poor installation on the '81 is probably right.

Re: Position of 4-speed trans hump?
« Reply #4 on: February 01, 2018, 05:18:24 PM »

Ryoko

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Re: Position of 4-speed trans hump?
« Reply #5 on: February 01, 2018, 06:43:47 PM »
It was spot welded, just not very well. The shape of the hump panel was not a very close match for the transmission tunnel in the floor pan. So the spot welding was hit and miss with some large gaps where the two parts didn't match up well. Seam sealer to the rescue! I think I can do a bit better than that. A few minutes with the hammer and dolly has made a big difference already.

glenn911

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Re: Position of 4-speed trans hump?
« Reply #6 on: February 02, 2018, 08:00:32 AM »
My '74 hole was cut with a torch, very crude looking, but factory.
'79 400 4 spd esprit
'78 455 WS6 auto
'74 461 4 spd T/A

firebirdparts

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Re: Position of 4-speed trans hump?
« Reply #7 on: February 02, 2018, 09:41:34 AM »
We need a sticky on this.  The problem is finding a meaningful point of reference.  Maybe someday!
I want to be like Paul Kenny when I grow up
Joe Bays
1977 Y82 4-speed (red interior)
1978 Skybird 350
1978 Redbird 305
1979 Redbird 301 4-speed
1992 Lincoln Mark VII LSC/SE (red)
1970 Datsun Pickup
1953 Chevy pickup (converted 4x4)
1988 T-bird Turbo Coupe

mz-formula

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Re: Position of 4-speed trans hump?
« Reply #8 on: February 02, 2018, 12:06:31 PM »
I will get on this when I get home from work.  I have a 100% bare '75 T/A 4 speed shell that had a console and still has the brackets.  My '75 formula is a 4 speed car but has no console.  That car has dimples on the tunnel where the brackets would have gone.  I will get some measurments on both.

pontiacstogo

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Re: Position of 4-speed trans hump?
« Reply #9 on: February 02, 2018, 12:12:01 PM »
My '74 hole was cut with a torch, very crude looking, but factory.

Mine too - first time I saw it I was like 'Oh crap - it's not a factory 4 speed'. 
1974 Trans Am - 400 4 speed 3.42 rear.


Ryoko

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Re: Position of 4-speed trans hump?
« Reply #10 on: February 02, 2018, 02:37:48 PM »
OK. I went outside and pulled the tarp off to go look. The hole in the trans tunnel on the '81 looks like it was stamped rather than torched. If it was torched, it was done very cleanly.

Now for the final result of where to put the hump panel -- After repeated measurements on the '81 and trial fitting the panel to match up the with the center console, the winning measurement seems to be 13-3/4" measured as shown in the picture below. I was measuring to the edge of the flange. But I decided that may not be the best place since there could be some variation in the flange width. So I'm now taking the measurement from the console mounting bracket to the rear edge of the opening in the hump panel as shown.


mz-formula

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Re: Position of 4-speed trans hump?
« Reply #11 on: February 02, 2018, 08:21:55 PM »
Not sure weather to chime in or not my Numbers are WAY different on my '75s.  But ... from an engineering standpoint ... I will for sure give my 2 cents on measuring, being that I am an engineer by trade.  My strong suggestion is to measure from the front floor pan seam with the firewall.  Why is that?  What located the console braces? Who knows. They were measured off of some other point and stuck there.  Looking at my Formula, their is nothing as a locating feature for the braces other than some long flats to sit on.  So, the tolerance stack-up will grow and grow.  If measuring from the edge of the floor pan, it should be pretty consistent, and you are really working with one measurement, in the direction away from the engine that you naturally want to progress, rather than a back to the brackets, (however they were located in assembly) then back forward.  My 2 cents...

SO... my measurements ... did things move for different engines / transmissions... I don't know... but .. here's what I came up with.

1975 Trans AM, was a Pontiac 400, with a Muncie 4 speed (still regret not having $200 to buy the trans too)



6 1/8" from the front edge of the floor pan to the edge of the hump.





9 1/4"" from the front edge of the floor pan to the inner edge of the shifter hole.





from the bracket, to the edge of the hump, 11 5/8"






and from the bracket to the back edge of the shifter hole, 14 3/4"


Sorry for the weird pictures... I didn't feel like wrestling 2 heavy doors out of the car when it is 17* outside.





mz-formula

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Re: Position of 4-speed trans hump?
« Reply #12 on: February 02, 2018, 08:36:14 PM »
Onto the Formula...

1975 Formula, Pontiac 350, Saginaw 4 speed.




6 1/8" from the front edge of the floor pan to the edge of the hump.





9 1/4"" from the front edge of the floor pan to the inner edge of the shifter hole.

isn't that aluminum plate sweet ... (Thanks dad for hacking up the hole like a beaver, then covering the hacked up hole with a further hacked up aluminum plate) early 80s shifter swap gone wrong... way wrong.




This Formula never had a console... It has nothing to locate those brackets on





so ... From the top of the theoretical corner of the rearmost fillet...10 1/4" to the edge of the hump.

I cant give you the rear inner edge on this car because ... well... a beaver chewed it off in my dads driveway.  It was a big beaver ... about 6', and walked on its hind legs.


So... again...  not sure f things moved around based on different engines..  but ... this is what I came up with for a '75.

Ryoko

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Re: Position of 4-speed trans hump?
« Reply #13 on: February 02, 2018, 09:17:01 PM »
The measurement you're getting for the distance between the front lip of the hump and the front edge of the floor pan is off a full inch from what I got. I measured 7-1/8" for that. But I need to check that measurement on the 81 tomorrow. It's too dark to try to pull the tarp off and do a measurement tonite.

Ryoko

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Re: Position of 4-speed trans hump?
« Reply #14 on: February 03, 2018, 10:48:21 AM »
I got a chance to go outside and pull the tarp off the '81 to do some measurements. It's a good thing too. I measured the distance from the floor pan seam to the front edge of the hump panel and it was also 6-1/8". So it seem there is a significant difference in the console mounting bracket locations between the automatic and the 4-speed.

So the lesson here is "Don't Use The Console Mounting Brackets As A Reference Point!"

Thanks to mz-formula for catching that.

Re: Position of 4-speed trans hump?
« Reply #14 on: February 03, 2018, 10:48:21 AM »