frankiebdv

Hello everyone!

This is my first post so please forgive me if I am asking something stupid.

Last week I took the plunge and bought a 1984 928 with a 5 speed gearbox. On the drive home, about 140 miles, the car drove very well apart from one or two niggles.

The first thing I noticed was how much free play the gear linkage had when trying to select a gear. Difficult to get into 1st or reverse, 2nd and 3rd almost impossible but 4th and 5th relatively easy. Luckily most of the journey was motorway so hardly needed to change through the gearbox..

After trawling through the most thorough forum I could have wished to find I now know the shift linkage will probably be worn or out of adjustment so will be repairing that as soon as I can.

Another thing I noticed was the Tachometer is only reading around 1400 rpm when travelling at 70 mph, roughly half what I would have expected.

I have searched through many of the previous posts but cannot find any mention of 'under reading Tachos'.

Any thoughts on what may be the problem would be most welcome as I don't know where to start having never come across this problem before. All the other instruments work fine and the Tacho does not have an economy gauge at the bottom.

Apart from that I am well pleased with the car, have ordered a workshop manual and am looking forward to learning how it works and finding out how to keep it running as it should do.

Thanks very much, in advance, for any light you may be able to shed on the subject

Frank.

SeanR

Shift coupler and ball cup will be your main issues on the shifter. Time to upgrade to the Lizard shifter.

Tach wise, sounds about right to me. The car was built for top end cruising.

Welcome and congrats on the purchase.

Fogey1

Here are some notes from a Tx-Cal trip log on my '83. I think we have the same diff. numbers, 2.23, iirc.
2100 @ 75mph
2400 @ 80mph
1700 @ 60mph
3600 @ 80MPH 4TH
2400 @ 80mph
2100 @ 72mph
2100 @ 76mph
2300 @ 78mph
2600 @ 90mph
2800 @ 50mph 3rd
2000 @ 70mph
1800 @ 62mph
2250@ 78mph
3100 @ 70mph 4th
3000 @ 100mph
3000 @ 100mph "car at a fast amble"
2300 @ 80mph

I don't know what the story was at 2100, except the notes were spoken into a recorder and transcribed later. The trip was nonstop in both directions, so maybe my eyes were crossing.

Ducman82

WELCOME!

James Bailey

The 928 engine was designed to not have to rev very high to get the job done.

CatoBT

My 1978 is very difficult to get into reverse/1.st. The other gears are working fine.

I'm planning on taking it to Poland for complete repair of body/gearbox/engine during this winter.

Please let us know the results if you have your car in for repairs.

Rgds

Cato

smiffypr

IF you had a tacho off an early car, you could be seeing half the expected rpm.
The early (single distributor cars) have one tacho pulse per spark, the later cars with siamese or twin distributors only have one tacho pulse for every other spark (one pulse per spark on one distributor). Is your car a "euro" with an M28/21 engine with the siamese distributor?
Smiffy

frankiebdv

Thanks for all the replies and advice.

I have taken the shift coupler off the car, rubber bushes badly worn and the allen screw was loose in the coupler body so will get some bronze bushes knocked up in work this week and put it back together at the weekend.

As for the tacho, I don't think it has been replaced with another from an earlier car but without pulling the instument pod off I can't see any way of testing it.

I did have an idea of attaching another (8 cylinder tacho) but am unsure which wires to connect it to under the dash so maybe time get my thinking cap on.

The revs show less than 000 when it is ticking over and a max of 2,500 or so when giving it some welly.

By the way the car does have a twin distributor ignition set-up but don't know the engine code, is it stamped on the block somewhere?

Thanks again for the response and will let you all know if I manage to cure the tacho issue.

Cheers, Frank.

Landseer

Frank. Where you at?

Mrmerlin

the engine code is about 1 inch forward of the top radiator hose clamp and straight down under the hose on the engine block there is a pad about 2 inches wide and about 1 inch tall with a M28/??
and then an engine serial number possibly 84_ _ _ _

Maleficio

Buy a multimeter with RPM capability and compare readings.

smiffypr

As you have the twin distributor caps (known as a Siamesed distributor to distinguish it from the separate distributors on the cam wheels on the 32 valve engines), and you want an accessory tacho which will read correctly, you will need one suitable for a four cylinder engine.
If you can't find the tacho signal on the wiring diagram, let me know.

Landseer

The 84 tachometers are notorious for scattered behavior.

Dwayne did a write-up on his 84 tach and the things he did to the circuit film / rivets to fix it.

I have 2 84 cars with intermittent tach readings.

Dutch 928 fan

Same problem over here: I changed my instrument cluster with a second hand replacement to fix my speedometer, but now my tacho shows half the revs. Only after reading this thread I understand the issue: the replacement cluster is for a single distributor car and not for my 1984 s2 with twin distributor s...
Question that i have: what if i change to a matching ignition unit that would expect half the pulses? (i noticed my ignition unit, the control box right of the fuse panel) has been switched by the PO as was the instrument pod as well. So i may have to do a double switch of cluster and unit??)

smiffypr

To change your ignition system to the earlier one would involve many parts and many wiring changes, and you would end up with an inferior system.
Much better to change your tachometer to the correct one. If you only needed the new cluster to get the speedo working, why not fit your original tacho to the "new" cluster?