1987 LJ70 gearbox (R151?) broken (8 Viewers)

[Gubbtratt1]

A while ago I had the gearbox in reverse to keep the motor from spinning as I torqued the crankshaft pulley bolt. I had the clutch disconnected, so when it came to letting the motor spin freely I just forced it out of gear. At that point something broke, as it feels like the gearbox is in neutral, but I can't engage any gears and it is in fact still in reverse. At that point I just thought something had jumped out of place and could easily be fixed by removing the top cover. Today I got to actually removing the top cover, and apparently the top cover is very small and doesn't really expose anything, so that didn't help. I can't force it back into reverse, at least not with about twice the force it took to break it.

What could be broken? Is this something that has happened before?

How do I easiest disassemble it?

 

[AirheadNut]

There are several parts that could have broken, when I get home from work later today I can dig out some photos of when I had mine apart. Unfortunately disassembly requires completely taking apart both the transmission and transfer case, but that is really your only option I think. They’re not hard transmissions to work on; apart from basic tools you’ll need a couple of styles of gear pullers and a hydraulic bearing press.

 

[Gubbtratt1]

There are several parts that could have broken, when I get home from work later today I can dig out some photos of when I had mine apart. Unfortunately disassembly requires completely taking apart both the transmission and transfer case, but that is really your only option I think. They’re not hard transmissions to work on; apart from basic tools you’ll need a couple of styles of gear pullers and a hydraulic bearing press.

Thanks! I had anticipated having to properly disassemble it, though I had a bit of hope that it would be possible to split the gearbox with the transfer case still attached. I have the perfect opportunity to install 3:1 low range gears, as well as making a hydraulic press now though.

Can the gearbox be disassembled and assembled while still attached to the engine? I think that would make it a lot easier to work on.

 

[Gubbtratt1]

There are several parts that could have broken, when I get home from work later today I can dig out some photos of when I had mine apart. Unfortunately disassembly requires completely taking apart both the transmission and transfer case, but that is really your only option I think. They’re not hard transmissions to work on; apart from basic tools you’ll need a couple of styles of gear pullers and a hydraulic bearing press.

I found the photos in your build thread. Are there any parts (other than gaskets) that must be replaced, or can all bearings, shaft seals and specialty nuts be reused, assuming they're in good condition?

 

[sadam_husain]

Have you checked the selectors after forcing it out of gear

 

[AirheadNut]

Sorry I dropped the ball on photos, glad you found some in my build thread but if there is anything specific you would like to see let me know. I have lots more photos and am actually in the process of helping a friend replace the input shaft in his R151f so I can grab photos of anything inside the transmission.

You'll want to replace all the stake nuts (3x of them), the transmission output shaft bearing and there are a couple of o-rings and some oil seals that are good "while you're in there" items to replace. I put together a list of the parts, you won't need the input shaft, input shaft bearing or synchronizer ring, and the oil seals and bearing in the "Optional Parts" category are for the transfer case.

The gearbox has to be completely removed from the vehicle to disassemble it, there are two snap rings behind the front bearing retainer that have to come off in order to remove the transmission case from the intermediate plate and gear clusters. If you don't have it already, the FSM RM183E has complete disassembly and reassembly instructions for the R151f and transfer case.

Another thing I forgot to mention before is that you'll want a good set of snap ring/circlip pliers.

 

[Gubbtratt1]

Have you checked the selectors after forcing it out of gear

Is this what you mean?

They seem perfectly fine.

Sorry I dropped the ball on photos, glad you found some in my build thread but if there is anything specific you would like to see let me know. I have lots more photos and am actually in the process of helping a friend replace the input shaft in his R151f so I can grab photos of anything inside the transmission.

You'll want to replace all the stake nuts (3x of them), the transmission output shaft bearing and there are a couple of o-rings and some oil seals that are good "while you're in there" items to replace. I put together a list of the parts, you won't need the input shaft, input shaft bearing or synchronizer ring, and the oil seals and bearing in the "Optional Parts" category are for the transfer case.

The gearbox has to be completely removed from the vehicle to disassemble it, there are two snap rings behind the front bearing retainer that have to come off in order to remove the transmission case from the intermediate plate and gear clusters. If you don't have it already, the FSM RM183E has complete disassembly and reassembly instructions for the R151f and transfer case.

Another thing I forgot to mention before is that you'll want a good set of snap ring/circlip pliers.

Thanks! I didn't have the correct manual, so with that and the parts list I think I should be able to manage this. I'll ask if I need pictures of anything.

 

[sadam_husain]

Is this what you mean? View attachment 3913013View attachment 3913014
They seem perfectly fine.


Thanks! I didn't have the correct manual, so with that and the parts list I think I should be able to manage this. I'll ask if I need pictures of anything.

No I meant the actual selector forks inside the gearbox that shift and engage the gears, sorry not my pic and its a H55F gearbox not an R151 but the same principle of the gear shifter moving the selector forks around

 

[Gubbtratt1]

No I meant the actual selector forks inside the gearbox that shift and engage the gears, sorry not my pic and its a H55F gearbox not an R151 but the same principle of the gear shifter moving the selector forks around

View attachment 3913030

Those are what I believe (hope) is the problem, but on the R151F they aren't accessible without completely dismantling the gearbox.