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MG MGB Technical - Reverse Problem

Hi,
My 1980 MGB is giving me trouble with reverse. I have to fish around awhile before It will go in reverse. All forward gears are OK. This unit has a OD, the OD is not in when I am trying to put it in Reverse. I read in previous threads that there is a OD in 3rd however my OD only works in 4th. The information I read in the owners manual states this is correct so what is 3rd. OD

Cec
Cec Fry

'80 o/d only has o/d in 4th. Reverse issue needs a check of the hydralics first for determination.
Paul Hanley

Cec, which gears OD works on is governed by a switch on the box. Earlier cars allowed 3rd and 4th, last ones like yours 4th only so that's OK.

Your reverse problem is most likely not related to OD. I'd suspect the clutch is dragging (not disengaging fully. Your box will have sychromesh 1st gear so you may not notice a problem selecting that. Reverse doesn't though and will block up if the clutch is dragging.

Where is the biting point? If it is low on the floor maybe it needs bleeding, this often causes problems as it can be tricky to bleed. If not, it may be a worn cover, have sticking splines or oil on it.

A way to check for drag is to select 1st, then, whilst still holding the clutch fully down, quickly come out and into reverse. If this allows reverse selection it is because you have stopped the gearshaft rotation caused by drag by going into 1st. Rich.

Rich

Cec doesn't say if the clutch is dragging or not, he just says that he has to go "fishing" before he can get the gear. When you are fishing Cec does the transmission grate or does the lever just not want to find reverse position without any rude noises being heard.
Iain MacKintosh

Is the gear lever loose or firm when you move it around, shifting precision is much influenced by the plastic bearing on the lower end of the gearlever.

My reverse always needed a "firm hand" to engage, did it shift better before?
Willem van der Veer

I always find in my GT that changing into first then finding reverse (without lifting off the clutch) makes it easier.
Simon Jansen

My clutch is not dragging or the gears would be grinding.
It's the same as if the position don't exist for reverse. I have tried it with the engine shutdown and it's the same, wont go in reverse. I have moved around the gearstick(shift lever)to 1st, 2nd. etc.,then tried reverse still no luck.I sort of force it into reverse. When it finally finds reverse I can take it out and go to the other gears with the engine running and it will always go back in reverse, no grinding, perfect. But after travelling the car I have a hard time getting it in reverse again. I changed the oil in the gearbox and replaced it with 20W/50 last year but it was fine last year. I only drove the car 1000Kms since the oil change.
It's as if the position for reverse is not lining up with the lever. There is very very little play in ther gear lever. The car has 94000KM's and I have owned it for 5 years. The clutch free play seems fine and the other forward gears work fine as do the Overdrive. As one writer said it needs a "Firm Hand" but I fear I may break something.

Cec
Cec Fry

Cec, What position of moving the lever stops you making the selection? Is it blocked trying to get the lever left past the 1-2 gate or after that, when trying to pull back to engage reverse? Rich.

Rich

On my transmission the fork inside the tranny that selects reverse was loose and therefore was a tough go to get it in reverse.The tranny had to come it out to clear the problem.
Problems with overdrive in 3rd gear can be the sensor that projects into the area where the gear shifter fits. It's a spring fitted brass "bullet" that gets hit by the shifter in 3rd & fourth. If it's worn it doesn't "tell" the o.d. to engage.This is accessable from the area undr the shifter boot.
jim hilton

Rich,
when I drive the car after reversing it then It is hard to go in reverse. It's like no detent or opening between 1st and 2nd. unless I force it in reverse. Its fine in forward.
Cec
Cec Fry

Cec, You've had the car a while so will know if it's worse now than before. There should be a resistance to going left past the 1-2 position, to stop it happening by accident, and it should need a slap with the palm.

The resistance is caused by a spring/plunger/ball set-up and often the opposite problem happens, when the spring gets weak and lets you into the reverse gate too easily, so you grate reverse trying for 2nd in a hurry.

If it now needs more force then I don't know why, other than that assembly breaking or jamming or a problem slightly further down the selector chain with the interlock. I take it you can get reverse once across and into the reverse gate, so a selector issue, which if it gets too bad may mean taking out the box to sort. Maybe someone else has been here?

Rich

In my 76 MGB that I've had about a month, we were always having trouble getting it into reverse. Then my wife reminded me that when we had my 74 in 1974 (boy, that's 31 years ago), that I always slapped the shifter with my palm to put it in reverse. Ever since then, I put the shifter between first and second, give it a good slap with my palm, and it ALWAYS goes into reverse the first time.

Since my 74 was brand new when I bought it, I think that its normal for it to be a little hard to get into reverse. Probably protects the car in the long run - no fun accidently going into reverse at 2000 rpms.

John
John English

I recently went thru my wife's 80 B and did some repair in the tranny. I replaced the cluster gear shaft and the springs in the synchro bulk rings. The trans had been a little difficult at times getting into reverse even when rocking first to second and then slapping back to reverse. What I found was the gear teeth on the reverse gears were ground somewhat flat and not tapered as per earlier in its life. I took a dremel tool and radiused the surfaces back to their original shape and now it goes into reverse much easier. Hope this helps.
mwhitt

A slap with the palm is exactly what I meant with a firm hand!
Willem van der Veer

This Gt67, when going in reverse, feel and sounds like a limp( missing or broken teeth), and if i do not hold the gear lever, it jumps out.
the first gear is not sync, when engaged also sounds a bit funny.
second if engaged when in movment scratech a bit, but the 3rd and 4th are ok.

Alf
alfredo

Thanks folks i will try the slap the next time I drive it.

cec
Cec Fry

This happened to me on my 1977 MGB. The last part on my car that needed to be fixed. I figured now was either the time to have it rebuilt, or go with a 5 speed conversion. I went with the 5 speed Sierra.

Ray
Ray 1977 MGB

Something similar occurs in my 1974.5 MGB (4 speed with overdrive). Sometimes when I attempt to get into reverse, the stick simply won't get into gear. This happens even when I'm at a full stop. I can get into all the other gears quite easily. My parents, who bought the car new, told me that it was always this way.

What my Father used to do when this happened, and what seems to work for me, is to shift through the other gears and then try to get into reverse again. Occasionally I have to go through the gears twice to get it to go into reverse.

Once it does get in gear, it moves easily in reverse. The clutch isn't dragging either.

By the way, my problem occurs when trying to pull the stick back to put it into reverse. I can pull the stick towards me past the 1-2 groove resistance fairly easily (a firm tug seems to do). It's the downstroke that's the problem.

Jeremy
1974.5 MGB
photos.yahoo.com/nibblyfish
J. Palgon

Jeremy, Reverse relies on the ends of the teeth being angled to pull the gears into alignment as they slide into engagement. If the angles are worn flat on their ends there will be increased incidence of them butting together and not going in first try. Selecting another gear moves the gears and you can then try again. See mwhitt's post above for the fix.

Rich

Oh, I should have said that even with good reverse this will still happen from time to time and is quite normal, maybe 1 time in 10 would be reasonable. All of my cars have done it inc the present one which I've just rebuilt the box on so know the gear to be good. I guess having had older cars many of us will simply flick into another gear then retry reverse without thinking about it.

Rich

Rich,
Well it happens on my car about 1 in 2 tries. I don't really find it to be too much of a problem. If the angles are worn flat on the teeth, then they've always been that way. I just reconfirmed with my father that it has done this since the day they he bought it new in 1975.

Jeremy
J. Palgon

Hi Jeremy, then I would say no problem, some will be different to others and it was common on many older cars not just Bs. Happens on some new cars too thinking about it, guess we just accept it. It occurs to me that (and I mean absolutely no offence here) UK and other drivers used to manual gears may simply have grown up with these things. They aren't noted in books but i have no doubt someone in the distant past will have told us what to do if it doesn't want to go in. All this faults aside of course and I don't mean to make light of a genuine fault. Rich.

Rich

As everyone is saying, this is common to manual trans cars. What I do is put it in first, move the car an inch or two, then select reverse.

Works every time without fail.
Tom Balutis

This thread was discussed between 08/06/2005 and 16/06/2005

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