Transmission surgery... need expert advice

[addautomotive]

Hey folks,

After a few months of "nursing" reverse, it finally let go today. It's a 96 1.9TD with an "ATH" tranny. When I first bought the car, I was told the reverse idler was missing a couple teeth. At first it would "click" when you reverse. Gradually became more of a "clank", now it gone completely. I want to tackle this on the weekend, so I have a few days to gather the required artillery.

Here are my options:
Option 1: Transmission Surgery:I could actually disassemble the transmission and swap in a good idler. I have a spare 020 transmission from an '87 that I disassembled today, it has a a good idler. It also has a 0.71 5th, which I plan to put in the '96. :twisted:
Option 1 questions:
a)What do you think the chances are that ONLY the idler is damaged?
b)I need to know the RIGHT way to remove the housing. When I took apart the 87 tranny today, I just removed the shift rod and let the forks fall where they may. What is the proper way to do this, so that I can slide the housing up with all the forks in place? Do I put it in a certain gear, or do I need to remove the shifter mechanism from the housing?

Option 2: Transmission Swap: I could buy a transmission from a friend, but they are from A2 jettas.
Option 2 questions:
a)Will my electric speedo pickup on the 96 mount in an older A2 transmission?
b)Will the axle flagnes be the same?


Option 1 is my preference, because it wouldn't cost me anything and I the tranny is otherwise in great shape. My main concern at this point is finding out the PROPER way to slide the housing off without removing the  shift forks.

Thanks for any help,
Jake

[chrissev]

Hey folks,

After a few months of "nursing" reverse, it finally let go today. It's a 96 1.9TD with an "ATH" tranny. When I first bought the car, I was told the reverse idler was missing a couple teeth. At first it would "click" when you reverse. Gradually became more of a "clank", now it gone completely. I want to tackle this on the weekend, so I have a few days to gather the required artillery.

Here are my options:
Option 1: Transmission Surgery:I could actually disassemble the transmission and swap in a good idler. I have a spare 020 transmission from an '87 that I disassembled today, it has a a good idler. It also has a 0.71 5th, which I plan to put in the '96. :twisted:
Option 1 questions:
a)What do you think the chances are that ONLY the idler is damaged?
b)I need to know the RIGHT way to remove the housing. When I took apart the 87 tranny today, I just removed the shift rod and let the forks fall where they may. What is the proper way to do this, so that I can slide the housing up with all the forks in place? Do I put it in a certain gear, or do I need to remove the shifter mechanism from the housing?

Option 2: Transmission Swap: I could buy a transmission from a friend, but they are from A2 jettas.
Option 2 questions:
a)Will my electric speedo pickup on the 96 mount in an older A2 transmission?
b)Will the axle flagnes be the same?


Option 1 is my preference, because it wouldn't cost me anything and I the tranny is otherwise in great shape. My main concern at this point is finding out the PROPER way to slide the housing off without removing the  shift forks.

Thanks for any help,
Jake

I can't give you much help but I can tell you that there were two different axle flanges used on the 020 transmissions found in the 85 to 92 golf and jetta.  90mm and 100mm.  They are not interchangeable and if you want to put a 90mm flange transmission in a car that originally had a 100mm flange transmission, you need to swap in the correct flanges for the car.  I have really no idea what flanges you would find on a 96 1.9TD but I doubt they would be 90mm.  If you have the tranny out of an 87 car with a .71 fifth it is probably a 7A or a 7D and then it would have the 90mm flanges.  

As far as swapping parts between the ATH and whatever transmission was in the 87 car, I don't know what swaps and what doesn't.  Best way to tell I guess would be to compare the parts.  

Regarding the speedometer.  Unfortunately, the gears are all different on the various transmissions.  This is a problem with swapping transmissions.  The speedometer needle will move, but will not indicate the right speed.  Someone once posted something on here about how to correct this.  I can't remember who or what the topic was.  You might want to do a search.

Your destroyed reverse gear was caused by someone putting the car in reverse when it was still moving.  Reverse is not syncronized.  Don't do this people!

[addautomotive]

Your destroyed reverse gear was caused by someone putting the car in reverse when it was still moving.  Reverse is not syncronized.  Don't do this people!

It was HER! I swear!

Thanks for the help chris! I picked up a Bently today and will post the pics when the job is done.

[vwmike]

90 and 100mm flanges are for the most part interchangeable. The issue is that both need to have the mini-slip differential. The open differential flanges are a bit different. If you got an A2 trans with the mini-slip diff you could swap on the flanges from your other transmission and bolt it in. Your speed sensor will fit in the A2 trans, and so long as it has the same final drive it will read the correct speed.

If you want to do the trans surgery, then there are a couple of ways to get it apart. In both cases, obviously you have to remove 5th gear and the gear selector, as well as the drivers side CV flange. Do no pull the rod out that the forks slide on. When you pull the case halves apart, just push the rod through and the forks will then all be on the rod in the correct order. They will come right off as an assembly. There are 4 small 12 point bolts that retain the input shaft bearing. If you remove those then the bearing will stay on the input shaft and you can tap on the end of the input and pinion shafts while pulling up on the case half. Also, remember to remove the bolt in the bottom of the transmission as that is what holds the reverse idler in place. The other option you have for disassembly is to leave the 12 point bolts in to keep the bearing in the case and then tap or, more likely rig a puller to press down on the input shaft while pulling the case up and off. This will leave the input shaft bearing in the case so that you can then remove the gear stacks from the input shaft.

I would be nervous about taking this on in a weekend. There is always the possibility that one of the chunks from reverse has made it through the ring and pinion or one of the gears which would chip the teeth and eventually cause a problem. If you're lucky, the peices of reverse just got stuck to the magnet though. In any case, be sure you have another trans available to you if you get into a pinch and need something to throw in there so you can get to work on monday morning. Good luck!

[addautomotive]

Great replies... thanks folks. I've completely torn apart my "donor" tranny, and borrowed a Bentley manual. I think I'm on teh right track. I'll piost pics when I'm done.

[chrissev]

90 and 100mm flanges are for the most part interchangeable.

the flanges are interchangeable between the transmissions, but not between the axles.  ie, a 90mm flange will not fit a 100mm axle.  The 100mm flanges are the improved version, so you want them if possible anyway.

[vwmike]

90 and 100mm flanges are for the most part interchangeable.

the flanges are interchangeable between the transmissions, but not between the axles.  ie, a 90mm flange will not fit a 100mm axle.  The 100mm flanges are the improved version, so you want them if possible anyway.

Yes, the inner cv's will not directly interchange. I've heard of people using spacers to take up the slop as 100 CV's are thicker than 90's. 100's are kind of overrated though. I run 90mm cv's in my Rabbit for a couple of reasons. #1-They're plentiful - I can get them for free. #2- I prefer to keep the weak link outside of the transmission if at all possible. I think I've broken one inner CV. It cracked the cage in several places and deformed the inner peice that is splined, splintering the metal around the ball bearings. I installed a reman shaft and the outer cv started clicking within a day. It broke and came apart in a parking lot about a week later. I also completely grenaded an outer CV - it broke the cage into a million peices. I've also broken the input shaft bearing in a trans. Broke the teeth off the ring and pinion, and cracked a 3-4 shift hub. I guess my point is this - You can break just about anything, but even with 90mm CV's it's possible to break something in the transmission. If you go to 100mm CV's for power holding reasons then you're more likely to break the trans and not really likely to improve power holding capabilities.

[VWRacer]

The 100mm flanges are the improved version, so you want them if possible anyway.

Maybe so, but I have used cheap-ass 90mm VW CV's in my 250+ hp Ralt Formula Atlantic since 1997, and have broken exactly one...a 3-yr old one we had turned on a lathe to lighten.  

Fat tires, 10,000+ RPM and 250+ hp...90mm can do the job.  :twisted:

[vwmike]

The 100mm flanges are the improved version, so you want them if possible anyway.

Maybe so, but I have used cheap-ass 90mm VW CV's in my 250+ hp Ralt Formula Atlantic since 1997, and have broken exactly one...a 3-yr old one we had turned on a lathe to lighten.  

Fat tires, 10,000+ RPM and 250+ hp...90mm can do the job.  :twisted:

I think most of the reason they break more on the street is just because of uneven surfaces which can cause a lot of drivetrain shudder. Most of the times I broke CV's, the car was only making about 160-180 whp. I actually haven't broken any since it started putting down 200, but that may change once I get it back together with the new Air/Water intercooler  

[addautomotive]

Thanks for all the help folks, got the transmission back in on Sunday and it works like a dream. I got off REALLY easy... only the idler needed to be replaced. The 1/2 synchro collar had a couple small chips, but nothing severe.

The only problem I ran into was when I got everything buttoned back together. I couldn't get 1, 2 or reverse. Turns out I slightly bent the shift rod when I was manhandling the transmission out. Had to loosen that clamp at the end of the rod and play with the adjustment for a good 1 1/2 hrs before I had the shifter properly centered.

I'll post some pics later.

[srivett]

That's good news.  How did you get the cases apart in the end?  I've tried removing all the external bolts and pounding on the cases but they won't budge.  My 6 mm 12-point Lisle tool broke before loosening the first bolt so those are still in.   :?  I've got an 8 mm Snap-On tool and it is way better than the Lisle.

Cheers, Steve

[addautomotive]

I made a tool that bolts to the case, with a threaded rod that pushes down on the end of the shaft. That way the bearing is left on teh case, and you can disassemble the stack.

I'll post a pic tonight... I made it with about $10 worth of stuff from Canadian Tire... and they welded it for free!