4 SPEED OVERDRIVE GEARBOX MK2

[WJM]

Hi All. I have the chance of a 4 speed overdrive box. Is it worth fitting and do I have to make any chances to my car to do this. I have a MGB MK2 the box is from a MK2. Do I need any other parts as it comes as just the box. Is the clutch and slave clyinder the same. Is the wiring there for overdrive or do I have to fit a wiring loom. As you can see I am not sure what is involved. Does the box fit on the engine without any modifications. Thank you for your help. Regards John.

 

[Banjo]

The overdrive unit is a definate advantage if you do any amount of cruising. If you are almost exclusivily in town, stop and go then it's just added complexity.
It should fit in the tranny tunnel without any body modifications, It's really just a different tailshaft from an installation standpoint. You will also need the switch, and I'm not sure the wiring is already there. If not it's pretty basic, and I'm sure fabricating it would be simple. That's about it though.

 

[Bruce74B]

Yes, I agree, it SHOULD just bolt right in too. The wiring was there orginally, as is the switch, but is all exposed, so it may be gone now. The good part about that is that it is not hard to wire up. Furthermore, make sure the dipstick filler hole lines up with the access in the floor (there were a few minor differences in the Mk2's) and you should be set.

If you are going to pull the engine/tranny yourself, make sure you elevate the rear of the car enought to provide clearance for the OD unit when putting the new one back in...it has to be a little bit higher than is necessary to get the non-OD unit out. Otherwise, it is like the manual says, "reinstall in reverse order of removal" and will bolt right in.

Good luck!

Bruce /ubbthreads/images/graemlins/cheers.gif

 

[Jim 67B]

The gear box will bolt in and does use the same drive shaft as the non-OD box. Be aware there are two 4 sysnc OD boxes. One is a top fill box. It has a speedo output of 1280 tpm. Since your car is a 72 it has a 1280 tpm speedo. You know what I mean by top fill, it has a dip stick like on your car. The other box was installed in the rubber bumper cars and is a side fill box. No dip stick, just a filler plug on the right side of the box. These are 1000 tpm speedo output boxes. It is not possible to change to speedo output without taking the gear off the main gear shaft in the tranny. If you are looking at a late model OD box, keep the speedo error in mind and also note that 75 and 76 MGB's had 1000 tpm speedo's that were the same size and style as the one in your car. If it is good OD box, go for it. /ubbthreads/images/graemlins/cheers.gif

 

[WJM]

Thank you guys for replys. This sounds good to me . Is there any way of testing the box before fitting or do I just take a chance. Thanks again. Kind Regards John. /ubbthreads/images/graemlins/cheers.gif

 

[Banjo]

That's a bit tougher. You can check the operation of the soleonoid, and you can look at the mechanicals in the box. But the overdrive is only electrically contorolled. the soleonoid opens or closes the flow of hydraulic pressure (generated by the rotation of the transmission parts) that engages the OD unit. So it really has to be tried out while driving. Or you have to be able to set up some kind of test rig to simulate driving conditions.Unless someone here knows a way that I haven't heard of, which is very possible.

 

[Bruce74B]

There was a thread a few months ago about this. When I read it, I thought it would be easier to install the unit and test drive it for just one application...unless you have a club that might have something or that you want to go to the trouble of building a test unit and make available for others to use.

If it is the right unit for your car, I would just go for it /ubbthreads/images/graemlins/driving.gif

Bruce /ubbthreads/images/graemlins/cheers.gif

 

[Radford]

I bought an O/D unit from a shop here in Atlanta, they have such a test rig and in talking to them I was told they had it because there was nothother way to realy test. Picture at https://www.atlantaimported.com/GBMGBOD.asp