BJ8 Tranny Issue - Slightly hitting gears when shifting

[pkmh]

Hello all, Not quite sure what my problem is just yet regarding my tranny. Problem so far is minor but symptom nonetheless is, during normal acceleration and after depressing the clutch pedal, I almost always feel as though I am lightly hitting against a gear tooth when I shift from first to second gear and from second to third (never from third to fourth and if I change gears at very low acceleration, problem is even less noticeable). Never a crunch or bang but a "feel" or slipping of the gears when shifting, but ever so slightly. Could it be a clutch or hydraulic problem? I will replace the flexible hose, slave, pin and re-bleed. As for the tranny oil, I do use the Valvoline 20W 50. Before changing the tranny oil however, I had this problem when I purchased the car but never figured out what oil was used prior. And what I know so far about tranny oil, is a product called "Redline" which may possibly eliminate the slippage sensation. Haven't investigated, yet. Until I get to examine the aforementioned possibilities, I also figure it could be the synchros. Anything else I left out? But for the moment and assuming the clutch and hydraulics are okay and there are no complaints about the oil I am using, I so far see there are two different type synchros offered on the market. One made of bronze and the other steel. For a 67 BJ8, can someone shed light on this topic and anything else that could relate to this problem? Figure I gather as much info before adventuring further. Much appreciated. Paul

 

[bob hughes]

Paul

Are you trying to shift too quickly? These old girls need a bit of time in the ear change department.



Bob

 

[pkmh]

No Bob, Not at all. I sometime would even try double shifting, (or that is to say, use the clutch to let out the shifter, then use the clutch again to put into gear. Same results). When I had my old Healey, this was not an issue unless as you say, shift too quickly. Then I felt the gears grind a little. Now, someone said to me once to determine if your synchro's are working or not, try at low speed, change without using the clutch. I've been afraid to do that and some say that is not entirely a true test, anyway. I noticed that when downshifting, the synchro's work, but more effort putting into gears than with my last Healey. Any helpful clues from this?

 

[Patrick67BJ8]

No Bob, Not at all. I sometime would even try double shifting, (or that is to say, use the clutch to let out the shifter, then use the clutch again to put into gear. Same results). When I had my old Healey, this was not an issue unless as you say, shift too quickly. Then I felt the gears grind a little. Now, someone said to me once to determine if your synchro's are working or not, try at low speed, change without using the clutch. I've been afraid to do that and some say that is not entirely a true test, anyway. I noticed that when downshifting, the synchro's work, but more effort putting into gears than with my last Healey. Any helpful clues from this?

Are you sure the clutch is fully disengaging?

 

[pkmh]

The only test I am aware of in determining if the clutch is fully disengaging is at a stand still. Pedal fully depressed, the car stands still. As I lift up on the clutch pedal, the car proceeds to roll. I currently have about a few inches of pedal play before movement is felt. Seems good to me, yes? Is there some other knowledge I'm missing? When I did bring this matter up with the previous owner, he said he never had a problem with the transmission but added that no work was ever done to the clutch. Car was sitting for a while before I bought it, so maybe I need to start with redoing the slave area and test again. Clutch itself "seems" okay. Any other thoughts?

 

[Keith_M]

The recommended oil for my 62 BT7 is 30W non-detergent oil, and I'm pretty sure it's the same for a BJ8. The non-detergent part is important. Since your clutch doesn't seem to be the culprit, you might try replacing the oil and see what happens. It won't hurt anything, and if it works, it's a cheap fix.

 

[57_BN4]

Paul, I think what you are describing may be quite normal behaviour of this design of gearbox. I can feel the engagement teeth knock into each other on each shift which is different to a modern type gearbox where you don't really feel anything. Not a clashing gears feel, just two heavy pieces of steel pushing each other out of the way once the synchroniser has equalised the speeds.

The steel synchros were on the last of the cars, possibly all BJ8s.

Andy.

 

[pkmh]

Andy, You explained it better than I did. Thanks! Yes, it is like a knock and not like a clash. So, is this normal? My first Healey was better behaved, no knocking, unless I revved higher and shifted too quickly. So, steel synchros were used on the later BJ's or maybe all. Any thoughts on the bronze ones out there being as good or should one stay away from. Thanks!

 

[57_BN4]

There are definitely junk quality brass synchros being sold- they are machined badly so the contact between the braking cone and synchro inside is limited to the high spots and they just bypass (crunch). I vaguely remember seeing the steel ones available too.

The notchy-ness of a gearbox really comes down to the shape of the engagement teeth if everything else is ok. When they were new and sharp they probably slid past each other more easily but now after 50 odd years they are rounded and are no longer at the optimum angle which requires a little more push to get them to move. If the synchros are worn they'll baulk which adds to the effort required to change. Redline oil might give some improvement but it has a well earned reputation for escaping at a great rate.

A quick check of the clutch is to get everything hot and with the engine idling, *gently* nudge the stick towards 1st until the gears are just buzzing together, then press the clutch. The buzzing should stop fairly quickly. If it slows down and doesn't stop cleanly your clutch might be dragging or pilot bushing dry which will make shifting difficult.

Andy.

 

[PeterB]

Andy,
I am kinda experiencing thesame issues on a transmission that was rebuilt not too long ago. Can youexplain the clutch dragging or dry pilot bushing a little more in detail. Byclutch dragging do you mean not fully engaging from a bad slave cylinder or poorlybleed line?
Thanks

 

[57_BN4]

Hi Peter,

There are a number of reasons why a clutch won't disengage fully (pedal pressed) and a quick way to test if it is working ok is to check if the gears stop rotating cleanly when the oil is stinking hot.

The pilot bearing can transmit engine torque to the input shaft if it is dry, air in the hydraulics can prevent the clutch opening fully, missing dowel bolts can mean the gearbox is not aligned with engine, damaged lining can rub on the flywheel, disc can stick on input splines, worn out release bearing... there are a heap of possibilities that can be eliminated by one quick test. If the clutch checks out ok then the problem is more likely to be in the gearbox itself.

We often hear about a "reconditioned engine" but almost always a "rebuilt transmission". That may be a liability issue in that it is relatively easy to repair to new-condition all wearing surfaces in an engine but to do the same in a gearbox requires replacement of pretty much everything but the case. The engagement teeth that cause notchy shifting are on the gears which are unavailable today so however many miles your car has done will determine how nicely it shifts.

If you are experiencing baulking (refusing to engage a gear) or crunching then you may be a victim of junk quality synchros. The acceptable quality ones are CNC machined on all surfaces whereas the others are smooth/diecast looking on the outside.

Andy.

 

[pkmh]

Thank you Andy for all that info. It seems my clutch itself is behaving as it should. Still, I will go ahead and replace the slave, the flexible hose, slave pin and re-bleed. If my knocking of gears still exists, then I will probe into those areas as you mentioned above. I see there is a drop of brake fluid (assuming it's brake fluid) always dangling from one point of the flexible hose which at least tells me there is either a weakening in the seal (hose or slave bushing) or the hose has become fatigued. Since the previous owner informed me no work was ever done on the clutch and that I do have all these parts I ordered a short while ago, might as well do this as routine maintenance. I also have a new clutch, throw out bearing and pressure plate and as needed, ready. But if you can, please elaborate a little bit more in detail more about synchros "CNC" machined. I also want to inquire my thoughts about a company in mind and would PM you about it. Thanks! Paul

 

[57_BN4]

Hi Paul,

It might not be fair to say all repro synchros with smooth outer surfaces are of substandard quality but at least some are and that is good enough reason to be extra vigilant or pay the higher price for known good ones. The effort and trouble to find out whether they are any good after the gearbox is back in the car is just not worth it IMO.

I believe Dennis Welch makes the CNC machined ones, they have tiny machining markings all over every surface and are hugely more expensive than the others. I don't know what quality issues the steel ones of the later gearboxes may have.

The key to getting the synchros to work is having them bite onto the mating surface so firmly you need a screwdriver to pry them off again. This can only be achieved if the inner grooved braking surface makes very good contact with the mating surface on the gear. Lapping with fine valve grinding paste and marking with engineers blue (or a felt pen marker) will quickly show up how good the contact is. Even the DW ones I got needed a bit of lapping before I was happy with them.


Here is one of the lesser quality cones after being blackened with a pen and rubbed onto the gear- you can see how little is touching

A DW cone after the same treatment- pretty good even contact

Incidentally I found a pic showing the engagement tooth wear on a Triumph gearbox. The original pointed shape has been worn rounded over the years

Andy.

 

[pkmh]

Thanks, Andy. You've given me a lot to go on here. It will be a while before all is investigated, but I will proceed. Drove her today and enjoyed all the knocking she had to offered.