Bad 5th to 4th gear "grind"

[Leland Pate]

I've got a buddy with a '79 SC coupe. He is internetless so I wanted to post this to help him out.

His 915 won't shift from fifth to fourth gear... I even tried it and it just plain ole won't go... "grind... grind"...

I know the first suggestion is going to be toying with the shift coupler, but my gut instinct tells me that isn't the culprit. If the coupler were out of whack, it wouldn't shift from fourth to fifth, right? His gearbox just won't downshift from fifth to fourth. Very strange.

The 915 in question was apart no more than two years ago for a fist and second rebuild. It was done by another friend of his who suposedly knows Porsches, but I don't really want to say it was a professional job, you know.

I would hope if there had been serious wear on the fourth gear synchros (I can't speel today) they would have addressed it then and there.

So, what are the possibilities?

Could this be indeed a shift coupler problem?

Could it be related to the fact that his clutch cable is way out of adjustment?

Could an out of adjustment cable have ruined his fourth gear (only on the downshift???) ?

I told him, we'd fist try to adjust the coupler and the clutch cable, then if that didn't help, we'd drain the tranny fluid and look for signs of disaster etc.

Failing that, I'm not sure what to do.


Ideas are welcome.

[GrindingGears]

I like your first and second step.

GrindingGears suck!

[Joe Bob]

Look at the bushing and adjustments....then do the oil drain and check for debris.

Will it downshift if double clutched?

[Leland Pate]

Nope, it's like it's not even there... when you pull the lever back to where 4th should be, you get that horrible sound of very fast moving gears (that are showing no signs of even trying to slow down).

Not a bad idea to check the shift lever bushings too, thanks Mike.

I'm just really hoping it isn't a major failure. This guy really doesn't have the cash to go trowing around.

[Zeke]

Another thing to do is put the rear of the car safely on stands and go thru the gears. With no load, sometimes you can figure things out. For instance, I had a trans that would go into a gear, but wouldn't stay. Driving, it didn't even want to go inot that gear. On that deal, it was the dog teeth on the slider. They get to a certain point and then they just won't work anymore.

[Vipergrün]

Leland, are you sure it's not nicking reverse? Definately adjust the coupler/linkage/shifter. I had an issue with this. You should verify the R lockout is working as intended.

-b

[surflvr911sc]

I think Brad is on the right track. Do everything, bushings, coupler adjustment, clutch cable adjustment, engine/trans mounts.

On my Dads car, I did almost everything, still couldn't get it to stop nicking reverse. Ended up the mounts were allowing too much movement in the drive train. When they were changed the shifting was 100% better and the fifth to fourth grind was gone.

[Joe Bob]

Yeah....sounds like reverse is getting in the act here....

[DANNOV]

I had a similar problem once and discovered that the screws that hold the gearshift base had loosened and a slight movement of the base was affecting my shifts. This may not be the solution to his problem but any looseness in the base or coupler can have a huge effect on shifting and I would not jump to conclusions too early and assume the worst. Use the principle of "Ockham's Razor", i.e. the simplest explanation is probably correct. In this case the simplest explanation is some kind of misadjustment in the linkage. Its easy to troubleshoot the linkage to either solve the problem or eliminate this possibility. Why don't you install that coupler I sent you and see if that makes a difference.

[Leland Pate]

Thank you thank you thank you guys so much... I never thought about it actually hitting reverse.

That is a very likely culprit.

Plus it fits into the story of "it didn't used to do this until after Joe blow R&R'ed the tranny.

I bet/ hope it is just the coupler.

His clutch is way out of whack too.

When you disengage the clutch, the pedal feels like it doesn't quite disengage. Or rather, it doesn't feel like it's getting the intended travel when depressed.

Hard to explain.

I'm gonna get this guys car running like a top. We've already done a load of work to it. In fact, I've wrenched on Ken's car more than mine!

[Rondinone]

It certainly can be the shift coupler. When I first bought mine, it would not downshift from 5th to 4th, but was fine from 3rd to 4th. Adjusted the shift coupler, grinding went away.

[al lkosmal]

I had the same symptoms. I was nicking reverse. This happened after I had replaced all the bushings and put it back together. Took me a few tries, but it adjusted out.

[74-911]

Ater installing all new bushings in the shift linkage, I experienced the same problem with clashing reverse when downshifting from 5th to 4th....

This procedure for adjusting the shift linkage is in the 911 Tech articles and it works.

http://www.pelicanparts.com/techarticles/911_shifting_improvements/911_shifting_improvements.htm

[nostatic]

Originally posted by Leland Pate
In fact, I've wrenched on Ken's car more than mine!

that's a good thing, right?

[bit]

Hi Guys,

I created a similar problem when I installed a short shift kit into my car. I removed the Shift Coupler and replaced the bushings and then re-installed it. and installed it and installed it. I kept getting problems with 4th and 5th. I was certainly clipping reverse. I fugured out that it is best to align your shift coupler in 4th gear (not 1st like it stats in the 101 book and Haynes manuals).

My $.02

.Steven
1980 911SC