Manual trans noise

[Lokahir]

My 87 FWD wagon recently started to make this tapping noise that has something to do with the drive train. I first noticed it tapping from my gear shifter in could feel the tapping. After about a week I could hear the tapping when I drove around. The tapping is in synchro with the rpm of the motor and only taps when drive is engaged. Pushing the clutch stops the tapping. The clutch works fine and it shifts smoothly through all five gears. Any ideas on what this could be?

The wheel bearings, half shaft, clutch plate, throw bearing are all new ( within last two years). Maybe some ideas where to check for the noise or how to troubleshoot. I am handy mechanically but slow on diagnostics.

Any help would be really appreciated. Thanks in advance.

[marlinh]

Does the noise occur when you are moving or stationary? Is it a light metallic sound? Does it increase in frequency with rpm's or road speed? Please give us as much info as you can so we can hep you.

[dlb]

welcome, lokahir.

you said the tapping does not occur when the clutch pedal is depressed, and that it occurs when driving in time with the RPM. so my question is: if the shifter is in neutral and you let the clutch pedal up, is the tapping present? if so, that would indicate a worn out input shaft bearing.

[Lokahir]

Thanks for your quick replies. The noise only occurs when you are moving. If you are in neutral with clutch up there is not a noise. Once engaged the noise is tapping in sync with speed of car regardless of gear. It seems louder in fourth and fifth gear. The noise decreases when going uphill though.

The tapping is metallic and when coasting in gear is almost nonexistent ( flats, downhill ). I am still able to feel the vibration in stick shift. Does not tap in reverse.

Hope this helps. Is there a way to check the input bearing? Thanks again.

[dlb]

if you don't hear the tapping in neutral with the clutch up, it's not likely the ISB. since it's only when moving it might be as simple as a a CV axle. is it better or worse when turning or accelerating? either or both of those would point to CV axle.

it might be an idea to check the gear oil level in your trans too. check the FSM available for download here for instructions. there will probably be a 24-mm plug bolt that you will remove while the car is relatively flat. oil should dribble out, or you should at least be able to put your finger in the hole and feel the oil just below the hole. if you can't, it's possible your gear oil level is low enough to have damaged some other bearings in the trans. take a look and see to rule it out.

[Lokahir]

Thanks again. The half shaft was replaced when the noise first started because I thought it could be culprit. Drained and refilled transmission but neither seemed to help. The tapping seems to be coming from passenger side of car. Hard to tell where tapping is occurring because it only does it when moving. I am at a loss and don't want to drop trans unless necessary. Any other ideas would be helpful. Thanks

[dlb]

what about jacking up the front end and spinning each wheel to see if you can hear or feel the tapping then? might try with the trans both in gear and neutral. you might be able to pinpoint where the sound is coming from them. this doesn't sound like a typical wheel bearing presentation but it's possible, and would be a much easier fix than taking the trans apart or replacing it.

another question i just thought of: what if you are coasting with the clutch in, or shifter in neutral with the clutch pedal up? does it tap then?

[Petros]

it almost sounds like the input idler gear in the trans is missing some teeth. it would clip or tap everytime the gear comes around when the car is moving, it would be more noticeable when under load like acceleration. This gear engages the gear on the input shaft, from there is goes to the main cluster.

I have seen this problem several times, once on a 2wd tercel trans. It means the trans has to come almost all the way apart to replace it. If it is just the input shaft bearing, or even the input shaft gear, that can be replaced by lowering the back of the trans (by removing the bolts on the cross member) and than remove the cover plate on the back of the bell housing and extract the inputs shaft. the bearing race can get real pitted, or the gear could be missing teeth. That is easy enogh to replace if you can find a good one.

hopefully it is not the idler gear, that too can be inspected once you get the input shaft out by truning the trans and watching the teeth on the idler gear with a flash light.

Good luck.

[Lokahir]

There is no noise when in neutral and clutch up. I will spin wheels to try and pinpoint exactly where the noise is coming from. Thanks for all the good info, will let you know what I find.

Sunny 80F
Trades ENE at 15-20 mph
Surf flat

[dlb]

There is no noise when in neutral and clutch up.

just to clarify: even while coasting?

[Lokahir]

Hi again, we'll I finally got some time to check out the noise . I jacked up the front end as suggested and found where the noise was coming from. It was on the passenger side of trans right above where the half shaft inputs to trans. With no load on front end the noise was more of a clunking ( like something loose or broken ) instead of tapping.

In gear the wheel did not turn smoothly but would rotate a little then stop and then suddenly start turning again. It was like it was slipping.

Obviously something internal is not good. Any insight would really help, like is it worth repairing or just replace.

Thanks again,

78F Sunny w trade showers
Trades ENE at 15-25 mph
Surf NNE 3-5 ft

[Petros]

sounds like it might need a new diff, or the spider gears on the front diff. slight chance it is the inner cv axle.

do not drive it or it might completely bundle up and damage the trans too.

take the front cover off the diff (drain the gear oil first) and have a careful look at the front diff. and spider gears. If that checks out than remove the cv axle and rotate the joint around by hand and see if you can feel a clunk or too much loose play in the joint.

Both of these should just get replaced. the CV axle is easy, replacing the front diff requires removing the transmission, I would replace the whole assembly, including the front bell housing and diff, as a unit. to replace internal parts in the diff requires resetting the ring and pinion lash and is a very sensitive and difficult operation unless you have done it before. Easiest to just replace the front diff assembly (that includes the integral bell housing).