Rattle at top of 2nd gear revs

[DrJeff]

I get a rattle which can be heard and also felt through the gear selector as I get to the upper end of the 2nd gear rev range. It goes away immediately on a change to 3rd gear. It doesn't happen in other gears.

I was hoping someone transmission savvy might recognize this symptom?

Thanks

[justlooking]

I get a rattle which can be heard and also felt through the gear selector as I get to the upper end of the 2nd gear rev range. It goes away immediately on a change to 3rd gear. It doesn't happen in other gears.

I was hoping someone transmission savvy might recognize this symptom?

Thanks

Sounds like detonation to me.

[DrJeff]

Could detonation be so specific? The engine is running great otherwise. Since it only happens as I get to the top of the second gear range I thought for sure I would be transmission related.

How would I check for a detonation problem?

[Spittybug]

At what RPM is your rattle? You say the top of the 2nd gear range, but that can vary.

If you are inclined to test Justlooking's hypothesis, run some premium gas through and see if it still does it. The higher octane should make it go away if it is knock. Do you know where your static timing is set?

[David T]

Check the engine and transmission mounts for cracks. Check the fluid level in the transaxle.
David Teitelbaum

[DrJeff]

At what RPM is your rattle?

I can't tell right now, the car is off the road for a number of things.

[DrJeff]

Check the engine and transmission mounts for cracks. Check the fluid level in the transaxle.
David Teitelbaum

The mounts look old but okay. On a manual there a way to check the transmission fluid level other than through a drain and replace procedure. If so I should refresh the transmission fluid, as I've no idea how old it could be.

The shop manual says spec MIL-L-2105C or API-GLS. What modern equivalent should I ask for?

Thanks

[David T]

There is a level plug on the side. The level should be right up to the bottom of the threads when the car is cold and level. If you don't know what's in there or how long it has been in there, then changing it is a good idea. Just be sure to remove the level plug BEFORE you try removing the drain plug. Use 85W-90 GL-4 hypoid gear oil. Or if you want something better, on Lotus's we are using Redline MT-90 in the UN-1 Renault transaxle.
David Teitelbaum

[Rich W]

I get a rattle which can be heard and also felt through the gear selector as I get to the upper end of the 2nd gear rev range. It goes away immediately on a change to 3rd gear. It doesn't happen in other gears.

I was hoping someone transmission savvy might recognize this symptom?

Thanks

Hi Jeff,

Another part (and area) you may want to check is the heat shield over the top of the exhaust cross-over pipe.
The mounting points for these heat shields tend to rust through, over time (much more quickly in the Rust Belt)
and the easiest way to quiet this down is with one or more oversized stainless hose clamps. Start with one on
the "suspect side" where the shield appears loose or just put one on each end. A good short or long term "fix".

Later.
Rich W.

[DrJeff]

Okay it sounds like I have some weekend work to do. I'm a little curious how I'm going to get under the car while it's still level (so the transmission level is right) given that I only have ramps and jacks?

Fun.

[Spittybug]

Okay it sounds like I have some weekend work to do. I'm a little curious how I'm going to get under the car while it's still level (so the transmission level is right) given that I only have ramps and jacks?

Fun.

Want to put it up on my lift? I'm over here near the Coffee and Cars venue.

[DrJeff]

Want to put it up on my lift? I'm over here near the Coffee and Cars venue.

That would be very cool. Might have to wait a bit as the D isn't road friendly at the moment. I've got her disassembled inside and out to take care of a bunch of pre-EV projects.

Thanks
Jeff