MGB & GT Forum

I recently got another 77 MGB. I recently posted about it having problems down shifting into second, so I know the transmission probably has some issues. The clutch does feel a little spongy, and I have to press all the way to the floor to change gears. I changed the slave cylinder and bled the system, but it did little to make the clutch pedal feel better. If I release the clutch without giving much gas, the car does stall immediately, so I’m not sure if this is a clutch issue as much as a clutch system or transmission issue, if that makes sense. Thoughts?

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1977 MGB (White)
1977 MGB (Blue)

If the clutch doesn't slip, it sounds like an hydraulic issue. The clutch pedal shouldn't have to hit the firewall to change gears.


GMc

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Wait for me at the gate Tuffy, because without you they're never gonna let me in.

SDCH WTCH-X Twin Oaks Tuff Nutt
2008 - 2022

Greg, I’m going to change the hose on the slave (I should have done that when I changed the slave), but would that cause downshifting issues too? Also, I have no leaks on the master cylinder, but is it possible the master needs to be replaced? I’m kind of dreading doing that.

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1977 MGB (White)
1977 MGB (Blue)

I would measure the travel in the slave push rod to verify operation of the hydraulics. Any movement less than 3/8" and I would suspect some air remains in the system.

Andrew

So yep. If there any issues with the hydraulic lines, they’ll be taken care of now. While trying to get the nut of the clamp that hold the metal line to the rubber, I twisted and broke off the fitting on the metal line. I thought I had a good hold of the nut above the bracket while I wrenched off the rubber fitting nut, but apparently not. There was a lot of corrosion, so hopefully a new line and rubber hose takes care of my problem. At least the pedal pressure. I have a feeling i have a bad synchro gear or baulk ring. Thanks all for the advice!

Shayne

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1977 MGB (White)
1977 MGB (Blue)

Very possibly you have a worn clutch pedal to master cylinder pushrod pin hole. ANY lost motion in the entire clutch release system can lead to incomplete disengagement of the clutch and result in the clutch dragging the transmission input shaft which can make the synchronizers job quite difficult, hard shifting is the end result. If worn, the pedal hole can be welded up, and re-drilled to either the original size, or larger for the installation of a bushing which becomes the sacrificial wear surface and can be replaced if needed down the road. I went the bushing route on my wife's 1976 MGB and sourced the bushing from McMaster-Carr.

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"We the willing, led by the unknowing, are doing the impossible for the ungrateful. We have done so much with so little for so long, that we are now qualified to do anything with nothing." source unknown....

David, thank you for that. I went out and looked and the hole is definitely elongated. I put a few pics up. One is static and you can see light where the hole is elongated. The next two pics show the amount of travel, without changing the position of the master cylinder rod. How would I weld fill and redrill that? Is the piece that the cylinder rod clevis pin goes through removable, without having to disassemble the pedal box?

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1977 MGB (White)
1977 MGB (Blue)

Shayne,
The pedal will come out the bottom. Between the pedal box and the fender under the hood is a bolt that can be removed to free the pedal. There is a return spring inside that can be disconnected easily. Pull the clevis pin, and the pedal comes right out. I found a local performance fab/welding shop that welded up the pedal pin hole for $20, and I re-drilled it to accept a bushing, and replaced the clevis pin. I also replaced the pedal pivot bushing, got the pin and pivot bushing from Moss. McMaster-Carr supplied the clevis pin hole bushing. I ordered a couple each in different sizes. I will post back the part numbers shortly. It is important to carefully measure the pin hole location to the unworn part of the hole prior to having it welded up. I took a picture of my measurements and wrote it down as well. I re-drilled to original pin size utilizing my prior location measurements in a drill press before moving up to the larger size for the bushing. I did have to slightly shorten the bushing length to fit in the clevis, and used a right angle die grinder with a Roloc brown disc. This repair made a significant difference in the pedal action, and I have an extra bushing for later down the road. I used a Nissan PBC brake grease to lube the parts on reassembly. Fishing the pedal pivot bolt out and back in is a bit fiddly, but patience, a helper with pedal, a mirror, and good lighting are keys. Also I had to slightly loosen that bolt for free pedal action, so I used a tiny bit of blue loctite on final assembly.

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"We the willing, led by the unknowing, are doing the impossible for the ungrateful. We have done so much with so little for so long, that we are now qualified to do anything with nothing." source unknown....

McMaster-Carr part numbers are as follows: 2868T53/2868T54/2868T59/2868T61. I ordered two each to have spare in the future. Pretty sure I used the larger OD and wider bushing, but I usually order several sizes to have choices during that kind of fab work.

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"We the willing, led by the unknowing, are doing the impossible for the ungrateful. We have done so much with so little for so long, that we are now qualified to do anything with nothing." source unknown....

Dave, thank you! I appreciate the insight! I’ll be pulling the pedal tomorrow while I wait for new lines to be delivered. I just ordered the bushings from McMaster and the pedal bushing/spacer/spring from Moss. Thank you for the help!

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1977 MGB (White)
1977 MGB (Blue)



Edited 1 time(s). Last edit at 2024-04-27 07:37 PM by Sjmckean70.

I also have some insights about bleeding the clutch system. I'll PM you my phone number and we can chat about that if you like, lots of little tips that would need a really long post to convey. Just PM me back with your number so I know who is calling (I get lots of spam calls....).

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"We the willing, led by the unknowing, are doing the impossible for the ungrateful. We have done so much with so little for so long, that we are now qualified to do anything with nothing." source unknown....

Just wanted to thank everyone who helped me with some great advice, especially Dave Fogle. I had heard of the nightmare stories of people trying to get the clutch pedal out without taking the paddlebox off. I headed out to the garage tonight determined that I was going to get it done. 30 minutes later, it’s out! It’s amazing what you can do With the right tool and the right advice. The clevis pinhole and the clevis pen have both seen much better days. Now to find someone to weld fill so I can drill a new hole and install bushings that Dave recommended. With these medical tweezers, I’m confident I’ll be able to get the bolt back in. Thanks again!

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1977 MGB (White)
1977 MGB (Blue)



Edited 1 time(s). Last edit at 2024-04-29 05:42 PM by Sjmckean70.

Hi Shayne,
What was the outcome of your pedal repairs? I had PM'ed you some additional information regarding the bleeding issues I had, and my ultimate solution to them. Just curious and hopeful that you are back up and running.

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"We the willing, led by the unknowing, are doing the impossible for the ungrateful. We have done so much with so little for so long, that we are now qualified to do anything with nothing." source unknown....

David, I got the clutch welded and I redrilled, installed the bushings you recommended and the clutch operation is MUCH better, but it still doesn’t want to downshift into 2nd gear without grinding. I bought an OD transmission from Stannis MG in Georgia, so once I get that, I’ll be replacing it. I appreciate all the help though!

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1977 MGB (White)
1977 MGB (Blue)