Transmission findings!

[Vangruver]

So as some of you may or  may not know, I lost 5th gear on my transmission from a 90 TD with just shy of 490km. The head's been rebuilt and the car is running pretty good in all consideration.

I've been searching for a suitable diesel transmission with some luck, but in all honesty the more I looked and the more I calculated costs I found that it's not as simple as it seems.

What I've been winding up with is calculating ratio's and final drives with gasser trans versus diesel trans through this site http://www.scirocco.org/gears/ I've found that there is a lesser RPM if I go through an 8v transmission. Even with a 16v transmission I found that my engine's RPM will spin less with a gas trans,  than a diesel trans.

I've calculated it at 100kph, with a tire size of 195.50.15. That tire size is what I'll be using when I switch over to the summer tires in the next couple weeks.

Here are my findings.

Diesel Transmissions

Current [no 5th gear] transmission 020 4y
FD of 3.941 and a 5th gear of 0.894 = 3245RPM [+/-]

020 ACH [transmission I'm considering buying from another member]
FD of  3.941 and a 5th gear of .0745 = 2704RPM [+/-]

Gasser 8v & 16v Transmissions

020 ACN,AON,ASF,ASL
FD of 3.667 and a 5th gear of .0745 = 2516RPM [+/-]

020 AUG,9A,ACD,AEN
FD of 3.667 and a 5th gear of .894 = 3019RPM [+/-]

020 AGB,2Y
FD of 3.667 and a 5th gear of .912 = 3080RPM [+/-]


____________________________________________________________

Keep in mind that all these transmissions have the same first gear, and various ratios that are different from 2nd to 5th. So starting and cruising will be a little different.

My goal of this car is to convert it to become a commuter, with jaunts on the highway that cruise nicely at roughly 100-120km/h So far it looks like that ACN,AON,ASF,and ASL prove to have a lower cruising rpm than any of the remainder transmissions!

If it comes down to changing the way I drive in the city, then so be it. But fact of the matter is......there is a plethora of 8v gasser cars in this city, and I'm sure that I can source a fairly reliable transmission quicker than having to hunt for a exact or similar replacement diesel trans.

thoughts?

[Quantum TD]

I've gone over my opinions several times on the topic. I've tried a variety on my Rabbit over the years, and they conclusions are always the same.


1.5-1.6NA. If your motor is tired/weak, I'd stick to 7A, AGS, AOP, ACH or AVX (if you really want grunt). If you have a MK1, then you may also try these:  FF, FO, FN. They will only fit MK1.

1.6TD: Again, the same suite as above if you want to keep it in the power band, but if you want MPG, then ASF, ACN, ACL, AON, ASL. These are great for top speed. I wouldn't recommend them for an NA, because you won't have the torque to get moving in 1st or reverse (especially). The CHD and later MK3 transmissions that we really didn't see in the USA are also an option. They all have 3.67 R&P and a .75 5th gear.

1.9TD. You have to go with the 3.67 and .75 or .71 5th gear. Anything else would be a waste of power and you'd lose MPG.

[R.O.R-2.0]

So as some of you may or  may not know, I lost 5th gear on my transmission from a 90 TD with just shy of 490km. The head's been rebuilt and the car is running pretty good in all consideration.

I've been searching for a suitable diesel transmission with some luck, but in all honesty the more I looked and the more I calculated costs I found that it's not as simple as it seems.

What I've been winding up with is calculating ratio's and final drives with gasser trans versus diesel trans through this site http://www.scirocco.org/gears/ I've found that there is a lesser RPM if I go through an 8v transmission. Even with a 16v transmission I found that my engine's RPM will spin less with a gas trans,  than a diesel trans.

I've calculated it at 100kph, with a tire size of 195.50.15. That tire size is what I'll be using when I switch over to the summer tires in the next couple weeks.

Here are my findings.

Diesel Transmissions

Current [no 5th gear] transmission 020 4y
FD of 3.941 and a 5th gear of 0.894 = 3245RPM [+/-]

020 ACH [transmission I'm considering buying from another member]
FD of  3.941 and a 5th gear of .0745 = 2704RPM [+/-]

Gasser 8v & 16v Transmissions

020 ACN,AON,ASF,ASL
FD of 3.667 and a 5th gear of .0745 = 2516RPM [+/-]

020 AUG,9A,ACD,AEN
FD of 3.667 and a 5th gear of .894 = 3019RPM [+/-]

020 AGB,2Y
FD of 3.667 and a 5th gear of .912 = 3080RPM [+/-]


____________________________________________________________

Keep in mind that all these transmissions have the same first gear, and various ratios that are different from 2nd to 5th. So starting and cruising will be a little different.

My goal of this car is to convert it to become a commuter, with jaunts on the highway that cruise nicely at roughly 100-120km/h So far it looks like that ACN,AON,ASF,and ASL prove to have a lower cruising rpm than any of the remainder transmissions!

If it comes down to changing the way I drive in the city, then so be it. But fact of the matter is......there is a plethora of 8v gasser cars in this city, and I'm sure that I can source a fairly reliable transmission quicker than having to hunt for a exact or similar replacement diesel trans.

thoughts?

i, personally, love the ACN style trannies. i have 2 ACNs currently, one is in my wrecked GTI, its going to bet bolted into my 92 jetta with a TD in front of it..

the other one is in my 86 Golf. lots of VWs from 85-87 came with ASF, AON, ACN, ACL, and the diesel cars had an ACH (same as an ACN, but with 3.94 final) im sure you can find an 85-87 golf/jetta GL trans.. its gotta be from a GL or lower trimmed car tho, the GLI/GTI got close ratio trannies..

if you do nothing but city driving, i personally would stick a close ratio trans in there and be done..

[Vangruver]

it will be a lot easier for me to source a gasser transmission, even If I have to buy the entire car just for the transmission it will be easier.

Here in Vancouver, friends are practically giving away 8v gasser cars for 2-500 bucks. and they all have a resulted rusted through strut tower or haven't passed emissions.

i'll just buy it, strip it, and leave it!

[burn_your_money]

You should also do calculations at whatever speed you usually drive at in the city. When I am picking a gearbox I go with the 3 most common speeds I drive at and find the best box for those speeds.

I put a ACN in my golf and quite liked it, although acceleration is notably slower. If you do a lot of stop and go the taller final will likely hurt mileage.

Be careful when buying a box about the axle size. I see you listed the 9A in your list. That has 100mm flanges and you will need to change driveshafts. I would stay away from 100mm flanges because they are a lot harder to find and usually more expensive.

[Vangruver]

Be careful when buying a box about the axle size. I see you listed the 9A in your list. That has 100mm flanges and you will need to change driveshafts. I would stay away from 100mm flanges because they are a lot harder to find and usually more expensive.

didn't think about the city driving too too much, as my work commute is really short, and stop and go isn't in abundance.

As for the flanges....i took that into consideration, but the list I compiled for the calculations was based on a page I sourced and copied from. When it comes down to the details I'll look into the specifics with a magnifying glass

[rallydiesel]

I have an ACN in my 1.6td and I think it is the best trans for this engine. Especially if you have the fuel turned up moderately with the governor mod. I lost 5th gear on this trans and swapped in a .71 5th and it's even better but it's really only a minor difference.

[Vangruver]

I have an ACN in my 1.6td and I think it is the best trans for this engine. Especially if you have the fuel turned up moderately with the governor mod. I lost 5th gear on this trans and swapped in a .71 5th and it's even better but it's really only a minor difference.

Even more good news.

I'm kinda stoked now to have this all done!

[R.O.R-2.0]

ACN trannies are RELATIVELY easy to find also..

i just bought my 86 golf for $200, manual steering, no a/c, ACN trans.. it was a gold mine of parts. now im actually driving the car.

[Vangruver]

Posting up a "looking for" thread on my local forum had a friend save the day!

I picked up a 7A transmission last night, greasy, but its got all 5 gears and reverse working.

And I checked the ratio's, and they seem really good!

3.45/1.94/1.29/0.91/0.71 with FD of 3.94

Excited to put this in.

[stewardc]

I just bought and rebuilt a CHD from a Mk 3 TD for my Caddy. It's the ultimate 020 IMHO.

[Quantum TD]

I just bought and rebuilt a CHD from a Mk 3 TD for my Caddy. It's the ultimate 020 IMHO.

Except for that weak reverse gear on ALL MK3 transmissions.

[stewardc]

I just bought and rebuilt a CHD from a Mk 3 TD for my Caddy. It's the ultimate 020 IMHO.

Except for that weak reverse gear on ALL MK3 transmissions.

That's OK, I'm not  going back  . 

[R.O.R-2.0]

I just bought and rebuilt a CHD from a Mk 3 TD for my Caddy. It's the ultimate 020 IMHO.

Except for that weak reverse gear on ALL MK3 transmissions.

That's OK, I'm not  going back  . 

just put the reverse and idler gear from a 4 spd in there..

[Quantum TD]

just put the reverse and idler gear from a 4 spd in there..

I used to toss 4-speed transmissions. Now when i get them, I split them apart for the reverse gears, and toss the rest of the internals. The bell housings make a great, lightweight too for setting the timing on engines on the floor of your shop, and a way to test compression and start motors without having to lug an entire trans around the shop floor.