C36 first problem.. hitting rev limiter and not changing up a gear

Page may contain affiliate links. Please see terms for details.

cazyp

Active Member
Joined
Oct 23, 2010
Messages
266
Car
C43, Hilux
Hi, hope someone can offer some advice.
Tonight I floored the throttle as I have just a few times since owning the C36.
All other times the gearbox kicked down, the revs climbed hard and then changed up a gear at around 7000rpm. Excellent.

Tonight it kicked down and climbed hard as before but at around 6500/7000 rpm it seemed to hit the rev limiter and 'bounce' rerr, rerr, rerr (sorry - best I can do lol) almost like a massive misfire and I guess from redlining manual gearbox cars it was hitting the rev limiter rather than changing to the next gear. This would have been in 1st gear.

Foggy tonight so didn't dare see if the same happened in 2nd gear or 3rd :dk:

Any suggestions as to why??
Serviced with mobile 1 and gear oil done very recently - it has changed normally since this was done.
I put £25 of Vmax in about 2 miles previous - always run on Vmax.

Thanks for any help.
 
after doing that did it eventually change up or did it just bounce and completely refuse to change up? You could've manually (accidentally) had it in 1st gear? I'm not sure if the C36 G'boxes have steptronic though.
 
Hi. It was in 'D'.
It 'Bounced 6 or 7 times and I backed off the throttle. It then changed up as the revs dropped (I think - hard to say as it was all a bit of a shock!)
 
7000rpm,,,why. i drive much too fast on public roads but rarely go above 3500rpm no need to
 
I would start with checking the level of fluid in the autobox, see if it needs a top up.
 
7000rpm,,,why. i drive much too fast on public roads but rarely go above 3500rpm no need to

Thanks for the advice. Sadly it wont help in diagnosing the problem though.

I would start with checking the level of fluid in the autobox, see if it needs a top up.

Already done - on the level and at 80c. All is well there...

Perhaps it's not the rev limiter but a misfire? Pretty severe if it is.. and runs smooth at all other times? Not 'limp mode' afterwards either.
 
Last edited:
When you say you changed the gearbox oil , what oil did you use ?

MB boxes are very specific as to what is acceptable.
 
fluid level worth checking
 
As said, fluid level checked. Correct merc ATF fluid used. It has been ok since change about 1000 miles ago, just played up last night. Wondered if it could be a valve/relay type fault?
 
did you check it again, fluid could be leaking since the change, pilot bushing is a common prob worth checking
 
Not sure where pilot bushing is or how hard it is to check? Is this the seal around the electic plug on the drivers side above the gearbox sump? If so it's dry.

Wheels I'm pretty sure were not spinning. Tried it again today on dual carridge way and done the same again in second gear. Hit 6800rmp and then juddered/bounced off rev limiter instead of changing up into 3rd?

Am I right in thinking an auto shouldn't or won't hit rev limiter in D regardless?

No leaks, fluid level at correct level at temp..

Thanks for help so far.
 
Last edited:
You're certain it was in 'D' ??

My old W208 didn't change up when using the Tiptronic feature. It would just bounce on the limiter.
Although that was on a year 2000 car. I think later cars did away with the bouncing thingie (i.e. it would just change up).

So only time it shouldn't change up (on older Mercs, anyway) is when you're using Tiptronic.
 
You're certain it was in 'D' ??

My old W208 didn't change up when using the Tiptronic feature. It would just bounce on the limiter.
Although that was on a year 2000 car. I think later cars did away with the bouncing thingie (i.e. it would just change up).

So only time it shouldn't change up (on older Mercs, anyway) is when you're using Tiptronic.

100% in D. No tiptronic Box, just 2/3/D and a S/E switch for eco(!) and sport.
 
S is for Summer.

Check the level first. You have a dipstick if you have the S/E switch. Check when running at full operating temp. (20min drive)
 
S is for Summer.

Check the level first. You have a dipstick if you have the S/E switch. Check when running at full operating temp. (20min drive)

Ah' Summer! Thanks.

Done that. Level at Max when warmed up after driving today. Can't see any leaks.
I'm wondering is it an electric signal or a vacuum that tells it to change up a gear at 'red line?'
Could this be the fault..?
Thanks
 
I dont know these boxes as well as the newer type. I think there is some adjustment that can be made to them on the side with regards to the vacuum system. It needs some vac guages and some specialist knowlege I think.

I have a very good gearbox man in my area that I can ask if you want.
 
It is worth checking the vac pipes for splits and security.
 
I dont know these boxes as well as the newer type. I think there is some adjustment that can be made to them on the side with regards to the vacuum system. It needs some vac guages and some specialist knowlege I think.

I have a very good gearbox man in my area that I can ask if you want.

That would be good thanks.

It is worth checking the vac pipes for splits and security.

Will do today it it lets up raining! :thumb:
 
I dont know these boxes as well as the newer type. I think there is some adjustment that can be made to them on the side with regards to the vacuum system. It needs some vac guages and some specialist knowlege I think.

I have a very good gearbox man in my area that I can ask if you want.

Hi just wondered if you've had time to ask yet please. Not red lined it since posting but doubt anything has changed. Checked vac lines and all look/feel ok.

Also do you know the model code for my gearbox and what other mercs had this box please? It's just that although it works ok with the exception of the above it's noisy in N and P. No whir or whine in D though.
I'm guessing it may not last forever so on the lookout for a good replacement box or perhaps a rebuild if i can find someone for the future as it's the only thing that's letting this classic down a bit.
Thanks
 

Users who are viewing this thread

Back
Top Bottom