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Discussion Starter · #1 ·
Hi,
I am looking to swap the automatic tranny in my 72 1900 Manta to a manual. I am told I need a section of the fire wall that hold the clutch cable bracketry and the mount for the transmission. Anyone out there have a scrap car they would be willing to cut the firewall piece out for me or at least send me a picture that I can fabricate what I need, and a line on the manual transmission mount. Any information about doing this swap would be much appreciated also.
Thanks
Toomany
 

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Opel Key Master
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The tunnel is the same but the mounts are not, you will need the transmission mounts that are spot welded to the tunnel. You could possibly make a custom mount and run it, but possibly if you are doing a 5 speed, the auto mounts might work out better
 

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Opel Rallier since 1977
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The tunnel is the same but the mounts are not, you will need the transmission mounts that are spot welded to the tunnel. You could possibly make a custom mount and run it, but possibly if you are doing a 5 speed, the auto mounts might work out better
??? Hey, Keith... Don't all Manta/Ascona have the same tunnel mounts welded in the same place, for both AT and manual ????? (Unlike the GT and Kadett...) But I do not have an auto trans Manta here to check those welded in mounts and locations.....

The manual trans tunnel mounts (and I assume the AT mounts) have 2 threaded holes in each side; only one is used in the 71-73 years. (Both holes are used on each side in 74-75 with a different crossmember and rear trannie mount.)

The crossmember stays the same for 71-73 Manta/Ascona between auto and manual trans, but the rear trannie mount is different between the AT and manual models of the Manta/Ascona in 71-73. The '72 Manta rear trannie mount for manual trans is the same as for the later GT's per my part manuals. PN 682503. So I would hope that is obtainable from OGTS. So with the right rear trannie mount, I think the OP is all set in the rear mounting area of the stock manual trans with the crossmember that he has.. unless the tunnel mounts move.
 

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Opel Key Master
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No, you can probably look at part numbers for the tunnels them selves, but I converted two manuals to automatics, ended up using a wagon tunnel to get the mounts off, they are similar, but I was going for close to correct. On the 75, it had a catalytic converter so had to make it custom anyways
 

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Opel Rallier since 1977
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OP, off the top of my head you will need for the stock Opel trannie:
  • Console and upper shifter boot
  • Lower shifter boot if you want to be complete (This is mainly to keep fumes and dirt and noise out.)
  • Shifter
  • Pedal set, which has both brake and clutch pedals in one assembly
  • Clutch cable
  • Bellhousing, with throw out arm and adjustable stud, and lower shield
    • I think the braces from bellhousing to block are the same
  • Rear trannie mount (see above for more discussion on the tunnel mounts)
  • Probably wiring from the reverse light switch to the harness; the reverse light switch is on the lower right rear of the manual trans.
  • I am not sure about the driveshaft.
  • Not sure on the speedo cable
 

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Opel Rallier since 1977
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No, you can probably look at part numbers for the tunnels them selves, but I converted two manuals to automatics, ended up using a wagon tunnel to get the mounts off, they are similar, but I was going for close to correct. On the 75, it had a catalytic converter so had to make it custom anyways
Thanks for clearing that up, Keith. I only had 1 auto trans Manta and not for long... I guess that all goes along with not putting the clutch cable tube in the firewall.....So make different bodies but keep the same corssmember... LOL

I would assume one could make some small adapter plates to bolt into the AT tunnel mounts and then weld in nuts in those adpater plates for the crossmember in the right place? Or weld the adapters to the crossmember..... If one did not care about being 100% original....and if the offset was not too much.
 

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OP, off the top of my head you will need for the stock Opel trannie:
  • Console and upper shifter boot
  • Lower shifter boot if you want to be complete (This is mainly to keep fumes and dirt and noise out.)
  • Shifter
  • Pedal set, which has both brake and clutch pedals in one assembly
  • Clutch cable
  • Bellhousing, with throw out arm and adjustable stud, and lower shield
    • I think the braces from bellhousing to block are the same
  • Rear trannie mount (see above for more discussion on the tunnel mounts)
  • Probably wiring from the reverse light switch to the harness; the reverse light switch is on the lower right rear of the manual trans.
  • I am not sure about the driveshaft.
  • Not sure on the speedo cable
All valid points. You also need to drill the spot welds and remove the raised shifter portion used on the automatics from the transmission tunnel.

Make sure you use a Manta/Ascona shift tower and shifter as they are different from GT.

Make sure you use a Manta or Ascona bellhousing. It mounts the transmission at a different angle than a GT, and has a different clutch fork outlet location too.

You can actually keep the pedal cluster you have and just add a clutch pedal arm to the pedal cluster. Much easier than removing the brake booster, etc.

Block-to-bellhousing braces are a different bolt pattern for 4-speeds, they are narrower than automatic on the Manta.

Automatic speedo cable works, it’s just a tad longer.

Driveshafts are different, auto is shorter and larger diameter spline.

Transmission mounts in the tunnel are further back on the automatics, about 3” IIRC.

Of course you need a manual flywheel, clutch, pressure plate, and release bearing.

Another big one...you need a pilot bearing in the back of the crank!
 

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Opel Rallier since 1977
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You can actually keep the pedal cluster you have and just add a clutch pedal arm to the pedal cluster. Much easier than removing the brake booster, etc.

Of course you need a manual flywheel, clutch, pressure plate, and release bearing.

Another big one...you need a pilot bearing in the back of the crank!
IMHO, since you need/want to change the brake pedal too, just putting in the whole pedal set seems a lot easier. The booster is gonna come out anyway if the clutch cable tube needs to be added to the firewall.

Yep, forgot the flywheel and clutch! And just was thinking about the pilot bearing. I assume all the Opel cranks were drilled for it. (Some mopar small block actually did not get the crank drilled for a pilot busing if the crank was being built for an AT car..... causes some issues when converting.)
 

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IMHO, since you need/want to change the brake pedal too, just putting in the whole pedal set seems a lot easier. The booster is gonna come out anyway if the clutch cable tube needs to be added to the firewall.
In the 1980’s I converted a lot of automatics to 4-speeds when I was working for C & R. I personally liked the wide brake pedal from the automatic in conjunction with the clutch pedal.

As far as the clutch cable tube, we usually just riveted it in place with stainless 3/16” rivets. Didn’t require removing anything, just had to make the slot for the cable to pass thru in the firewall.

We weren’t building concours cars back then, just converting the gearboxes!
 
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Pics of the clutch cable pass-thru tube (with metal bushing).
432363
432364
432365


Here is the comparison of the 4-speed versus automatic bellhousing-to-block stabilizers.
432366
432367
 
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Opel Rallier since 1977
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In the 1980’s I converted a lot of automatics to 4-speeds when I was working for C & R. I personally liked the wide brake pedal from the automatic in conjunction with the clutch pedal.
That is a switch! Guess I ain't that keen on that combination.. what with 1000's of shifts done in a rally and the car pitching all around.
FWIW, I used to bend the brake pedal over towards the throttle pedal.....easier to heel & toe the brake and gas.
 

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Opeler
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yes i riveted or bolted on the clutch cable tube when i did a manta conversion. when i did a kadett it was just a flat plate and used 2 of the bolts from the master cylinder and then added two beside it. if you want it to be more " concours " then cut, weld, and paint. i can't remember on the manta but on the kadett you have to also create space between the trans and the floor on the right side for transmission linkage. for the crossmember i did a ******* solution but it worked really well. bolted a steel plate to the back of the trans and then to the auto transmission mount. I checked the driveline angle and it was fine. i had a machine shop drill the holes so they were clean. there are also a few other misc things like blocking off vacuum line that went to modulator. on my kadett i also had to adjust the tune a little as it wanted to idle too fast. for the pedals i swapped i just added the clutch pedal to the shaft.
 

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Discussion Starter · #17 ·
Pics of the clutch cable pass-thru tube (with metal bushing). View attachment 432363 View attachment 432364 View attachment 432365

Here is the comparison of the 4-speed versus automatic bellhousing-to-block stabilizers.
View attachment 432366 View attachment 432367
Pics of the clutch cable pass-thru tube (with metal bushing). View attachment 432363 View attachment 432364 View attachment 432365

Here is the comparison of the 4-speed versus automatic bellhousing-to-block stabilizers.
View attachment 432366 View attachment 432367
Any of the pictured parts available to buy?
 

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Any of the pictured parts available to buy?
I have tons of the stabilizer brackets. Plenty of the firewall bushings too.

Not sure on the cable pass-thru however. Don’t know how many of those I have.
 
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