BJ42 ongoing transmission issues (2 Viewers)

[TristanFF]

This all started with it not going into 2nd gear. I pulled the transmission and had a look inside and couldn’t find any obvious issues. I then reinstalled it to do some more diagnosis and found that the shifter seat was cracked and the shifter alignment pins were very loose. Replaced those. This actually seemed to fix it for a few days. Shifted into second gear no problem then one day I’m driving around and it loses 2nd again.

Condition of the original seat and pins:

After the new seat and pins were installed:

After talking to some local experts they suggested to take a look at the hydraulics. Master and slave were both leaking so those got replaced with OEM parts. The hose for the slave was also in rough shape so I put in a new one of those. Also changed the transmission fluid.

The saga continues. I still cannot get into second gear without double clutching. When I let off the accelerator in second it throws it back into neutral. Additionally, I put the transfer case in neutral to see how it shifts under no load and there is a rattle that seems to get a lot worse the higher the gear I’m in.

Video cycling through the gears under no load, t-case in N

Video of the how the noise changes when revved under no load. 3rd gear.

It is worth noting that this is a BJ42 H42 Transmission but has the BJ60 top plate on it. I have been told that they are interchangable and it has been running with this set up for probably 15 years now. We put a Terrain Tamer trans rebuild and T-case rebuild in 3 or so years ago because input/output bearings were completely shot. The dog teeth on 1st and second still appear pretty sharp and in good shape. There are no chips or teeth missing on the gears them selves. The 1st and 2nd gear brake rings look to be in decent shape with the original machining groves still visible.

I am going to do the same test under no load tomorrow with a stethoscope to try and roughly isolate where the rattle noise is coming from.

Any ideas?

 

[myusername]

*Warning: gearbox layman's musings*

That's odd, the shifter bush is a common issue for not shifting, I've come across this on an H55F where it wouldn't select gear, but I'm not sure if it can cause your other problem of the grinding and jumping out of gear unless the shifter was worn as well as the pins. Even then, seems odd

You didn't happen to take the transfercase off or touch the nut on the main/output shaft of the gearbox while you had it out? If it is loose the shaft could walk backward under decel and cause grinding + jumping out of gear. Seems more likely your issue is tophat/shift/bushing related tho

 

[TristanFF]

*Warning: gearbox layman's musings*

That's odd, the shifter bush is a common issue for not shifting, I've come across this on an H55F where it wouldn't select gear, but I'm not sure if it can cause your other problem of the grinding and jumping out of gear unless the shifter was worn as well as the pins. Even then, seems odd

You didn't happen to take the transfercase off or touch the nut on the main/output shaft of the gearbox while you had it out? If it is loose the shaft could walk backward under decel and cause grinding + jumping out of gear. Seems more likely your issue is tophat/shift/bushing related tho

I’ve thought about that nut but I haven’t had the tcase off since it was rebuilt. Second gear and third gear are able to shift about an 1/8 inch forward and backward on the shaft. Normal tolerance or?

 

[myusername]

I’ve thought about that nut but I haven’t had the tcase off since it was rebuilt. Second gear and third gear are able to shift about an 1/8 inch forward and backward on the shaft. Normal tolerance or?

You would have to refer to the FSM, I've only messed with the transfer side of them

From memory, that nut should be staked, that would be a relatively easy thing to check

I just checked a H55F I have lying around, by hand 1st, 3rd and 4th are tight and don't move, 2nd has a little give

 

[TristanFF]

You would have to refer to the FSM, I've only messed with the transfer side of them

From memory, that nut should be staked, that would be a relatively easy thing to check

I just checked a H55F I have lying around, by hand 1st, 3rd and 4th are tight and don't move, 2nd has a little give

Hmmmm okay. I’ll double check that. If you have any more ideas please let me know.

 

[Mark Jennings]

The description, pops out of gear sounds like a shift fork spring and detent issue, and as far as getting her into second….synchro clutch hubs (brass rings). Or if the spring and detent are damaged, broken or misaligned, would account for the pop out of second AND hard shifting.

 

[myusername]

The description, pops out of gear sounds like a shift fork spring and detent issue, and as far as getting her into second….synchro clutch hubs (brass rings). Or if the spring and detent are damaged, broken or misaligned, would account for the pop out of second AND hard shifting.

Agreed, most likely something to do with the tophat

Best and cheapest check will be to borrow a known good tophat and go for a test drive

 

[peesalot]

FWIW, losing 2nd usually means the rear bearing of trans has worn/failed letting the shaft slide back as mentioned. No there should not be 1/8 thrust travel on the gears. Given the noises in videos, I would think that the output of trans has moved back and is causing the gear interference noise in tcase. Remove tcase and you'll find the prob IMO. I had a 72 bronco that lost 2nd and I drove it alot using 1st & 3rd so just because it was fine for 2 days after pin fix dont mean diddly, means the oil was cold and held it together while you were driving.

 

[TristanFF]

FWIW, losing 2nd usually means the rear bearing of trans has worn/failed letting the shaft slide back as mentioned. No there should not be 1/8 thrust travel on the gears. Given the noises in videos, I would think that the output of trans has moved back and is causing the gear interference noise in tcase. Remove tcase and you'll find the prob IMO. I had a 72 bronco that lost 2nd and I drove it alot using 1st & 3rd so just because it was fine for 2 days after pin fix dont mean diddly, means the oil was cold and held it together while you were driving.

This is kinda what my latest theory has been. Would explain why second pops out as well cause the dog teeth wouldn’t be fully engaged.

 

[peesalot]

I thought fj40's were loud enough but those BJ's are rattle cans.

 

[myusername]

I thought fj40's were loud enough but those BJ's are rattle cans.

BJ's are better with a bit of rumbly vibration

This is kinda what my latest theory has been. Would explain why second pops out as well cause the dog teeth wouldn’t be fully engaged.

Maybe also check your oil level and that the seal between gearbox and transfer isn't compromised, you ideally shouldn't be going thru bearings / thrust in just 3 years since a rebuild unless something was messed up or damage wasn't picked up during the rebuild? There's a cover on the back of the box you can remove the check the staked nut was in fact staked and is still in place

 

[TristanFF]

BJ's are better with a bit of rumbly vibration


Maybe also check your oil level and that the seal between gearbox and transfer isn't compromised, you ideally shouldn't be going thru bearings / thrust in just 3 years since a rebuild unless something was messed up or damage wasn't picked up during the rebuild? There's a cover on the back of the box you can remove the check the staked nut was in fact staked and is still in place

I pulled the transfer case today. The output bearing on the trans seems to be in the right place also there was obviously some heat build up because the seal between the transfer and transmission was hard as a rock. Everything in the t-case looks pretty minty otherwise. Stake nuts were all still tight and in the right place. Oil levels were good (transmissions had 2 changes in 3 months since trying to figure this out) t-case was a little low and there was some seepage through the rear output gastet of the T-case so that tracks but yeah. Nothing to note as of yet. Pulling the transmission out tomorrow.