May have diff problem

[jasonhepp]

Calvin and others, I need some help.

Got my car back last week, wow so good to go for a drive. I missed her so much. Had to go for a plane trip and drive the car to the airport which is a lovely 30 min drive 100KMH all the way. The car feels so good with the CD playing, doesnt get any better.

Anyway, I have noticed that when changing gears after sharp acceleration as soon as I take my foot off the gas the back end feels like it hits a small bump and then again (although not as noticeable) on re-acceleration. I thought it may be a suspension problem but this seems O.K. I've never had a car with diff problems but I suspect this may be the cause. Does any of this ring a bell with anyone. If it is the diff, whats the best way to get it fixed, ie can you get a reconditioned one, new one or try to fix ??

Otherwise, car is going really well. Still enjoying the site.

Calvin, now I am back with Esprit wheels I will contact the people you referred me to.

Thanks

Jason

[cnh1990]

It might not be tranny problems. Check the easy things first. I would look at the half shafts. Rotate the rear wheels forward and backwards, have a look at the play or feel for the play that might cause the bump as you let off the accelerator. If you are not familiar with how to check it enlist the aid of some familiar with worn universal joints or drive shafts.
Calvin
PS Forgot to mention to jack the car up or have the rear on stands with front wheels chocked before you rotate the wheels.

[lotusguy]

Calvin and others, I need some help.

Got my car back last week, wow so good to go for a drive. I missed her so much. Had to go for a plane trip and drive the car to the airport which is a lovely 30 min drive 100KMH all the way. The car feels so good with the CD playing, doesnt get any better.

Anyway, I have noticed that when changing gears after sharp acceleration as soon as I take my foot off the gas the back end feels like it hits a small bump and then again (although not as noticeable) on re-acceleration. I thought it may be a suspension problem but this seems O.K. I've never had a car with diff problems but I suspect this may be the cause. Does any of this ring a bell with anyone. If it is the diff, whats the best way to get it fixed, ie can you get a reconditioned one, new one or try to fix ??

Otherwise, car is going really well. Still enjoying the site.

Calvin, now I am back with Esprit wheels I will contact the people you referred me to.

Thanks

Jason

Jason,

Before you go all crazy trying to track down the culprit. Your symptoms sounds suspiciously like Motor or Tranny Mount problems. These aren't really the best engineered items I've seen, and it's not unheard of to see them fail relatively early due to the harsh environment they live in. Although Lotus uses all sorts of heatshielding, the motor mounts, especially on the engine exhaust side are subject to great amounts of heat which shortens the rubber mount's life tremendously.

To check for these, have someone else rev your car from idle to say, 3k or 4k RPM and then lift off suddenly while you observe the engine/tranny from both above and below for excess movement or shaking. Also, the bolts securing the engine/tranny to the mounts have been known to frequently come loose, so check these and torque them to their proper settings as well.

If it turns out to be the mounts, these can be replaced relatively simply without removing the engine /tranny using a floorjack to raise them up sufficiently to slip the old ones out and the new ones in. Hope this helps...Jim '85TE

>> Edited by lotusguy on Tuesday 17th December 18:28

[cnh1990]

Good one Jim, engine mounts could also make a bump.
Calvin

[lotusguy]

cnh1990 said: Good one Jim, engine mounts could also make a bump.
Calvin

Calvin,

Thanks for your kind words. Your suggestions regarding the half-shafts and CV joints is a good thought, but I would think these, as any rotational parts, would produce vibrations somewhat continuously, although they may not be noticeable at higher RPMs.

The reason I suspect the motor/tranny mounts is firstly their reputation for failure and secondly, the symptoms Jason is experiencing are exactly what happens when these fail. Jason's descrption is not very empirical, being somewhat subjective in nature.
The mounts, if faulty, are just starting to go because I have heard failed mounts produce an extremely loud clunk when the engine settles back down from the torque which lifted it and have actually seen an engine move sufficiently as to pop the engine cover off...Jim '85TE

[jasonhepp]

Guys,

Checked the mounts. The RHS one looks fine, the LHS doesnt look like it been tightened enough as there is about 1/8" gap from the rubber mount to the clamping plate (you can see the mount bolt). I have tried to tighten but both sides are absolutely stuck. Could not move at all. The bolts dont look rusted. The most I could do was rotate the whole bolt/nut but even this required an extension lever. I wouldnt do any harder without worrying about shearing the bolt or rounding the nuts (which is already starting to happen).

Tried to put some packing rope wrapped tightly around the bolt to help take up any movement, this has reduced but not stopped the tail end kick. Could not see anything else so I am thinking this is the problem. Any further suggestions?.

Compliments of the season to all and I hope you all had a safe time most of all. For me I took the family for a 3 day drive (no lotus unfortunately) to see the south cost of Victoria (state in Australia) - route is called the Great Ocean Road. Lovely travelling trip, Lotus would love it. Spectacular scenery but a bit chilly - 15degC for a summer in Oz is cold. Must be hard for you guys with the snow. our main problem is the heat although in Victoria not too bad, will only get the occasionaly really hot (40degC) day.

Cheers

Jason

[cnh1990]

Let's have a working descrption. Off the side of the engine is the mounting leg held on to the engine with (3) M8 X 35 caphead bolts with washer/lock washers. At the bottom of this leg is a single M12 X 100 that holds the leg to rubber mount. There are (2) buffer washers, one in between leg and the rubber. The other on the bottom of the rubber held on with a nut for the M12 bolt. Then there are (2) M8 X 20 bolts with washers that hold the rubber mount assembly to the frame through the mounting flanges of the rubber mount. Check to see all buffer washer and other washers are there. Also the correct length of bolts. Check the for rubber falling apart as the left side is the exhaust side and old mounts eem to fail on that side the most. Now has the engine ever been removed before? The mounts are for specific sides and can not be swaped as they do have different part numbers with a color code. They call out for engine mounting rubber RH blue and LH pink. Has the car been in a wreck on that side? If so you may want to take some string and do a dimensional check of the measure points to see if the frame is square if you suspect the car has been in a crash that would affect the mounts to shift.
Good luck,
Calvin

[lotusguy]

jasonhepp said: Guys,

Checked the mounts. The RHS one looks fine, the LHS doesnt look like it been tightened enough as there is about 1/8" gap from the rubber mount to the clamping plate (you can see the mount bolt). I have tried to tighten but both sides are absolutely stuck. Could not move at all. The bolts dont look rusted. The most I could do was rotate the whole bolt/nut but even this required an extension lever. I wouldnt do any harder without worrying about shearing the bolt or rounding the nuts (which is already starting to happen).

Any further suggestions?.

Cheers

Jason

Jason,

It sounds as if your left side motor mount has deteriorated and should be replaced. The rubber is subject to extreme heat on the left side due to it's close proximity to the heat of the manifold and exhaust, this can cause it to 'set' in a compressed state revealing the 1/8" clearance you see.

As I mentioned in an earlier post, you can loosen all the mounts, engine and tranny, and by placing a floorjack and a 2X4 piece of wood under the sump, you can raise the engine sufficiently to remove and replace the mounts. It will be a tight fit as you can only raise the engine a couple inches at most. Be sure that all your rubber coated washers and heatshields are intact as these do offer reasonable protection to the mounts.

You failed to mention your tranny mounts at all. These should be checked and serious consideration made toward replacing them as well as they will certainly have been distorted (possibly permanently) by the movement of the engine. Again, you can get just enough clearance to swap these out as well using the methods described above. Of course, you don't want to torque anything down til all the mounts are changed. Hope this helps...Jim '85TE