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930 Transmission rebuild and gears!!

Hi,

The transmission in my 930 shifts well enough, but grinds sometimes on 2nd and more frequently on 3td. I can live with it and if I shift gingerly it doesn't grind. However I want to replace the synchronizers in 2 and 3. Basically I want to make the car as perfect for me as possible, enjoy it and then either make the decision to keep or sell it. If I take the trans out for a rebuild I would very much like to swap gears for something sensible.

Problem is when I start to look at prices I am seeing $500 - $800 per gear! Any ideas? Maybe I don't need to replace all of the gears?
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Old 10-30-2017, 04:52 PM
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There are several threads here on this topic. You may want to do a search on gear ratio to pull some up. There are a few that intrigue me, as I also want to swap out gears but have never felt ready to invest in it.

Here is one thread, and I will go find the other and post it to. There are more.

I think one interesting thread to me are the proposed changes to bring fourth down a bit to roughly the same as a 915 5th, then spread 1,2,3 to allow good start from stop while avoiding too much rpm loss/torque loss between gears. Matt offers a 2nd gear that sounds good for back road corners, etc.

Here is one:
930 Transmission, Gear Selection
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Old 10-30-2017, 05:32 PM
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Here is another:

If you had to...
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1988 930 coupe - Silver Metallic
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Old 10-30-2017, 05:46 PM
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Ummm...what do you mean by the term sensible, we are talking about a 930 here. Not too many folks out there would ever use the term sensible and 930 in the same context.

If you are working with a basically stock 930, then changing out the final drive ratio (ring-n-pinion) to a lower ratio would be the least expensive option. This will give you better low speed acceleration at only a slight loss in top end speed. Really, who needs to do 160 in a street car anyway. If you track the car then trans gear swaps might make better sense.

A bolt on set of headers and an upgraded turbo with larger intercooler really wakes these cars up as well.

So you've got to ask yourself what it is you want out of the machine....hell it only costs money :}

Mark

Last edited by full quack; 10-30-2017 at 08:20 PM..
Old 10-30-2017, 08:18 PM
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Mark,
Excellent point, a Ring and Pinion might be better. My car has a K27 and a 964Turbo Intercooler. It is nowhere near stock! I don't track the car. I am also looking at a shorter 2nd and 3rd gear.
Really there is no easy option concerning price!
Thanks Chris
Old 11-01-2017, 05:32 AM
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What is it that people don't like about the stock gearing?

I like it just the way it is. If it were a track car that would be different. But that tall second gear is like having an automatic. I'm in first or second around town 80% of the time. Just run the RPM's up a little.
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Old 11-01-2017, 07:04 AM
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Wink

^

I would say it just the opposite. The stock 930 transmission is good for the track if it is a more open track having few or no corners under 60mph. The only way to keep the cams and turbocharger "on the pipe" is to redline to 6,700rpm in each gear. Not good for back road twisties.

Now , if you are just going to the store to get some bread or milk what difference does it make?

Rahl

Last edited by 356911930; 11-01-2017 at 08:45 AM..
Old 11-01-2017, 08:42 AM
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$500-800 per gear set is reasonable, especially if these are street gears with the standard gear tooth design (iow not high strength but noisy race gears). If you are swapping out 2nd and 3rd, then you're talking about only $1000-1600. Slide them onto the shafts

In contrast, a proper made ring & pinion is a lot more money, and cost a lot more to set up. An 8:41 seems to be the most common short R&P, and IMO it turns your 4-speed into a 3-speed by making 1st so short it's nearly useless -- think stump-pulling granny gear in an older pickup).
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Old 11-01-2017, 10:27 AM
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Quote:
Originally Posted by full quack View Post
. . .

If you are working with a basically stock 930, then changing out the final drive ratio (ring-n-pinion) to a lower ratio would be the least expensive option. This will give you better low speed acceleration at only a slight loss in top end speed. Really, who needs to do 160 in a street car anyway. If you track the car then trans gear swaps might make better sense.

. . .

Mark
Quote:
Originally Posted by Carbster09 View Post
Mark,
Excellent point, a Ring and Pinion might be better. My car has a K27 and a 964Turbo Intercooler. It is nowhere near stock! I don't track the car. I am also looking at a shorter 2nd and 3rd gear.
Really there is no easy option concerning price!
Thanks Chris

One thing to consider about a final drive ratio change is if you use the car for a lot highway driving (like me) . . . cruising at 80mph with +/- 3K RPM (70 is about 27-2800) is absolute bliss - I couldn't tolerate higher RPM cruising.
Old 11-01-2017, 10:34 AM
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One thing to consider about a final drive ratio change is if you use the car for a lot highway driving (like me) . . . cruising at 80mph with +/- 3K RPM (70 is about 27-2800) is absolute bliss - I couldn't tolerate higher RPM cruising.
Agreed -- another argument for changing individual gear sets and not the R&P.
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Old 11-01-2017, 10:35 AM
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gears

Ring and pinion would be cheaper and would give you a 'boost' in all 4 gears.
I know the problem. I constantly go back and forth between 3rd and 4th.
My 4th will last forever, because it gets very little use.
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Old 11-01-2017, 10:43 AM
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Ring and pinion would be cheaper and would give you a 'boost' in all 4 gears.
I know the problem. I constantly go back and forth between 3rd and 4th.
My 4th will last forever, because it gets very little use.
Ha ha - you and I are just the opposite; most of my driving is highway (part of the nature of where I live), so it is in 4th the majority of the time.
Old 11-01-2017, 10:46 AM
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Piggybacking on here a bit... you didn't mention 1st gear sychros? That seems to be the one that needs love 99% of the time...

Can anyone chime in on how much work it is to just change the first gear synchros if needed, assuming you do it yourself? Is that an easy to get to gear, or is it buried and other gears need to be removed first?

Is it possible to own a 930 that allows downshifts into first at 30-40 mph without double clutching/grinding? Mine is fine on the street and at stops, but downshifting on the track at speed is more questionable....

Bo
Old 11-01-2017, 12:47 PM
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Yeh, I guess I didn't think thru my replay very well, and was only thinking about how I use the car.
I only drive open country roads where the posted {sic} speed limits are 35-45mph. Which is ideal for hard 2nd and 3rd gear romps, don't see much of 4th or 1st.

To answer Bo's question "down shift into 1st at 30-40 mph"...with a 930 4spd...umm...not likely, maybe with a G50 5spd trans???

Next your going to ask if you can smoothly find reverse too....

Mark

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Old 11-01-2017, 03:12 PM
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Quote:
Originally Posted by full quack View Post
To answer Bo's question "down shift into 1st at 30-40 mph"...with a 930 4spd...umm...not likely, maybe with a G50 5spd
Nope, no way. IIRC, a G50/00-01-02 hits redline at 35MPH. Maybe a G50/52 will do 40, but still, ain't gonna happen.

BTW, grinding gears doesn't mean the gears themselves are actually grinding. If they were grinding, they'd be destroyed.
Old 11-01-2017, 03:17 PM
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Is it possible to own a 930 that allows downshifts into first at 30-40 mph without double clutching/grinding? Mine is fine on the street and at stops, but downshifting on the track at speed is more questionable....

Bo
What's wrong with a bit of double clutching? I do it almost every time and the gears slide in like butter if you hit it right (slightly higher RPM for slightly longer than my gut tells me). On the other hand without it.....griiiiinnnnnddddd
Old 11-02-2017, 10:27 AM
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What's wrong with a bit of double clutching? I do it almost every time and the gears slide in like butter if you hit it right (slightly higher RPM for slightly longer than my gut tells me). On the other hand without it.....griiiiinnnnnddddd
My synchros are brand new and I still blip shift, up and down. Makes the gears come together liked butter.

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Old 11-02-2017, 08:08 PM
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Years ago I added the Andial 8:39 R&P to what was mostly my track car. Economical upgrade that I'm still happy with today. MPH changes from the 9:38 to the 8:39 are below:

1st gear @ 6.5k rpm - 52mph to 45mph
2nd gear @ 6.5k rpm - 90mph to 78mph
3rd gear @ 6.5k rpm - 132mph to 114mph
4th gear @ 6.5k rpm - 188mph to 163mph

A buddy years later built a big hp 930 and re-geared his to match 2nd-5th on a 915 box iirc. 1st gear was good to 72mph @ 7k rpm and riding with him as he geared down to 1st for turn 3A at Pacific Raceways was pretty cool. He shifted a lot more than I did each lap but had an "active" 4-speed. On the street his 1st gear was not much fun...

Paul Guard also suggested ratios for me before I went the 8:39 route. I did add his GT 50/80 LSD and sold the GT TB diff I had been running. That 80% lock really settled the rear down under heavy braking.

Factory
1st 2.250
2nd 1.304
3rd 0.893
4th 0.625

Paul Guard
1st 2.780
2nd 1.737
3rd 1.038
4th 0.767

Rob's monster
1st 1.736
2nd 1.303
3rd 1.000
4th 0.767
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Old 11-03-2017, 12:06 PM
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Originally Posted by flightlead404 View Post
What's wrong with a bit of double clutching? I do it almost every time and the gears slide in like butter if you hit it right (slightly higher RPM for slightly longer than my gut tells me). On the other hand without it.....griiiiinnnnnddddd
Shifting the 930 trans on the track takes paleological time periods to do... I tried double clutching... that took EVEN longer. The instructor looked at me like I was nuts...

Anyone who can quickly double clutch a tail heavy 930 through (or even close to) a turn in ANY gear at speed is my hero .

I just wanted to make sure my experience is normal. Down shifting into 1st approaching a stop sign at 10-15 mph is no problem. Reverse, no problem...

But heaven forbid I come to a slow turn where the car slows down to 30 mph, I fall off the boost, and miatas fly by... Shifting to first gear would be awesome... But the gearbox doesn't like it...
Old 11-03-2017, 01:46 PM
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Just a couple points. The aftermarket ring and pinions currently available make way more noise than any of the new gears on the market. Those old Andial ones have been gone for years. I sold my last Ricardo made one to a Pelican about six months ago. Buyer beware if you care about noise.

My gears run $1095. Albins recently dropped their prices to $936.

Expect installing a ring and pinion to be about 12 hours of labor. Expect gears to be around 8. The pinion depth and backlash set up, if done well and with the right tools will be about 4 hours to do. At an average shop rate of $100, that’s $400. Ring and pinions are usually around $2500-2800. If you do the math that puts gears and a ring and pinion at about the same cost. This assumes you do 3 gears.
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