V8 4 speed gearbox - difficulty with reverse.

jp928

Active Member
#21
Have looked into this some more, now that I know a bit more about the structure of the rear mount - mine is the large cast item, not the fabricated type shown in the parts book. Its bolted to the base with 4 bolts. The two at the rear I can see how to hold the bolt heads while undoing the nuts, but the front 2 heads look extremely difficult to reach even with th exhaust removed. One I can get a screwdrive end onto to hold against torque on the nut, but the other I cannot see a way to reach. Are these bolt heads captive in any way, or is a special tool needed ? eg a ring spanner with the ring at right angle to the spanner stem? Crow foot open ?
 

harveyp6

Well-Known Member
#22
I did loads of clutches and gearbox work (surprise surprise) on those and I don't ever remember having problems accessing the top of those bolts, they are not captive, but I certainly didn't have to make a special spanner to get on them to hold them whilst undoing. If I had I would still have it, like the other little "special" spanners I made. I can't remember exactly what I used, but it would have been a normal spanner. My guess would be a 1/2" x 9/16" AF Britool offset ring spanner.
 

harveyp6

Well-Known Member
#23
Just a thought, maybe it's that I had the rear of the prop removed at the slip joint that gave me better access, if you're trying to just remove the mount with the propshaft in place I can see that restricting access.
 

jp928

Active Member
#24
Harvey, My problem is with the front 2 bolt heads, so I doubt the prop shaft is relevant...the one on the left I think I can get a screwdriver through a hole in the front face of a brace to load the bolt head, but on the right side access is obstructed. I have a half moon spanner, but even with that I cant reach the bolt heads.
thanks
 

colnerov

Well-Known Member
#26
Hi, Try a combination spanner, on upside down. TBH the first spanner I grab for any job is a combination spanner because it has an open end and a ring, the shallow angle makes it less likely to 'screw' off side ways with load.

Britool combination spanner.jpg

Colin
 

jp928

Active Member
#27
The rear bolt heads can be reached easily with a ring or open ended spanner. Unfortunately the horizontal plates are braced to the body with vertical plates between the two bolt heads, and at the front, so the front bolt cant be reached from the rear, and the body of the box is too close to give access from the front. The only option I have now is a 1/2" crows foot (as in the last pic), placed by a 3/8 socket extension. Going to try in next day or two.
 
#28
hey guys, I'm having both of these issues since some years. now I figured that decreasing idle speed mitigated the getting into reverse issue. However it slips out constantly. Now, I'm not able to look into it on my own and asked a mechanic to check the gear linkage, gearbox etc. He was wondering if he needs to lift the engine before even starting to look into the gearbox, gear linkage, reverse selector things… can you help me understanding this, thanks
 

harveyp6

Well-Known Member
#29
If the problem is with the gearlever, or the remote linkage it can all be inspected and fixed without removing either the engine or the gearbox. If it's internal then the gearbox can be removed on its own leaving the engine in place.
 

Penguin

Active Member
#30
hey guys, I'm having both of these issues since some years. now I figured that decreasing idle speed mitigated the getting into reverse issue. However it slips out constantly. Now, I'm not able to look into it on my own and asked a mechanic to check the gear linkage, gearbox etc. He was wondering if he needs to lift the engine before even starting to look into the gearbox, gear linkage, reverse selector things… can you help me understanding this, thanks
change the gearbox mount! the gear lever gaiter tries to pull the box out of reverse, if the back of the box is sitting low because the rubber mounts of sagged the problem is exaggerated, i have cured numerous cases of jumping out of reverse by changing it, including gearboxes which have been rebuilt by myself and others
 
#31
change the gearbox mount! the gear lever gaiter tries to pull the box out of reverse, if the back of the box is sitting low because the rubber mounts of sagged the problem is exaggerated, i have cured numerous cases of jumping out of reverse by changing it, including gearboxes which have been rebuilt by myself and others
hmm, where would I get a new one. Wins doesn't list it, no?
 

jp928

Active Member
#33
Yes, thats the rear mount. I did mine with only dropping the big cast mount off its mounts, Bell housing supported with jack and wood block, undid the nuts at an angle, and with some difficulty managed to get the old unit out, and the new one in. Would be much easier with exhaust dropped, but it can be done. To get the front right mounting bolt undone I used a spanner as in the the pic - 3/8 socket bar size gets in there well. With the old one out you can make a new one if you get 2 of the rubbers as used on the rear mount of an LT77... pic 2.
Now I can get full stroke of the lever for reverse.

 
#34
This morning I took a look together with the mechanic and he thinks the entire linkage needs to be overhauled, in addition to fitting a new rear bush. Now, I was wondering if you can help me collect all the replacement parts which go into overhauling the linkage. Would be great. Thanks
PS: the mechanic meant he needs to unmount the propshaft and exhaust to be able to push the engine to access stuff…
 

jp928

Active Member
#35
Make sure your problem isnt the mount before doing big stuff, like dropping the whole gear change mechanism. There is a steel plate on the back of the gearbox that sits on top of the rear mount. When the mount has sagged, its gets closer to the top rear edge of the big cast iron mount casing. Based on what mine looks like with a new mount, the steel plate should be around 5/8" above the cast mount - can do a real measurement if that would help - its still up on the jacks.
 
#36
Make sure your problem isnt the mount before doing big stuff, like dropping the whole gear change mechanism. There is a steel plate on the back of the gearbox that sits on top of the rear mount. When the mount has sagged, its gets closer to the top rear edge of the big cast iron mount casing. Based on what mine looks like with a new mount, the steel plate should be around 5/8" above the cast mount - can do a real measurement if that would help - its still up on the jacks.
could you provide a pic of how it looks with the new, I reckon one could see the difference, no?
 
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