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RC
Joined: 25 Mar 2007
Posts: 2636
Location: Australia
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 Posted: Tue Oct 12, 2010 2:18 am Post subject: Auto tranny hot up thread |
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Welcome to the most useless thread ever.
Who has a slushbox? Who would want one? and even if you had one, why would anyone want to rebuild one, let alone modify it?
Disassembling and cleaning valve body. Pistons were polished.
Pressing new bushes in oil pump. Easiest one of about 6 bushes to remove and replace.
Performance mods time. The clutch plates in the forward clutch drum were increased from the original 4 to 5 friction plates and an additional steel plate. Similar to a motorbike multi plate clutch. The circlip grove in the clutch drum was machined higher internally. The circlip retains the pressure plate. The pressure plate was machined down. A thinner circlip was also fitted and these three modifications combined, allow for the additional plates and set the end float.
This modification blocks the oil flow to the accumulator, a spring loaded piston that resides in the large bore here. It`s purpose is to provide a slow and gentle gear change by allowing the pressurized oil to compress a spring. I don`t want that. Blocking the flow into this chamber permits full pressure to act upon the clutch and band pistons. Faster, firmer, harder shifts.
Most important modification is the oil cooler. The 924 case is not adapted for the cooler fittings like the later 944s and 24S are. Hot oil returns from the torque converter at a sufficient flow and pressure. The case needs to be drilled and tapped for the line take offs. The internal return port needs to be blocked to divert flow via the cooler. Port is drilled, tapped and plugged just like the accumulator port.
That is the transmission part of the transaxle. It simply mates together with the differential portion. After all clearances have been measured and shims calculated and fitted of course. Makes it a bit harder when all the diff carrier and pinion shaft bearings have been replaced as well.
Easiest part, just 4 nuts.
Cheers
_________________
World`s quickest 924 2L slushbox
| Allan @ DTA wrote: | | I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards |
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Rich H
Joined: 10 Jun 2007
Posts: 2665
Location: Preston, Lancs, UK
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| Posted: Tue Oct 12, 2010 2:32 am Post subject: |
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Wow - hope it's worth it...!
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec |
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Tue Oct 12, 2010 3:06 am Post subject: |
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Impressive. And people call me a toofah fanatic! Only a true toofah fan would go to this much trouble  I love it!
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erstwhile owner of just about every 924 variant ever made |
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ic932
Joined: 11 Feb 2005
Posts: 1104
Location: UK
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| Posted: Tue Oct 12, 2010 7:23 am Post subject: Re: Auto tranny hot up thread |
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| RC wrote: | Welcome to the most useless thread ever.
Who has a slushbox? Who would want one? and even if you had one, why would anyone want to rebuild one, let alone modify it? |
Well as it happens  Just took ownership of a 86 944 auto. I'm seriously toying with the idea of mating it up with a S2 engine as a stopgap measure..and for the fun of it too. Might see some limitations on the 3speed so I've got my eyes peeled on your work.  |
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924guy
Joined: 29 Dec 2003
Posts: 2088
Location: Port St. Lucie, FL
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| Posted: Tue Oct 12, 2010 9:35 am Post subject: |
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wow, i didnt know anything about "my grandpa, The Don" before this, THANKS!
but really, i find this interesting. what kind of performance gain are you shooting for?
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Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
Performance by Pasha |
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RC
Joined: 25 Mar 2007
Posts: 2636
Location: Australia
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| Posted: Fri Oct 15, 2010 3:50 am Post subject: Re: Auto tranny hot up thread |
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| ic932 wrote: | | Well as it happens Just took ownership of a 86 944 auto. I'm seriously toying with the idea of mating it up with a S2 engine as a stopgap measure..and for the fun of it too. Might see some limitations on the 3speed so I've got my eyes peeled on your work. |
You know Dave, if you spend a little time driving around in traffic and prefer your hand on your wife`s leg rather than your stick, then you may even enjoy the slushbox.
IMO it`s not only the 924 NA auto that`s gutless, let`s be honest - the 924 NA is gutless. Having not much torque anywhere really, but with low down torque in particular needed for good acceleration in an auto, the anemic little motor is struggling. Especially so in US trim where it is down up to 35Hp to start with. I have found that a supercharger dramatically improves the low down torque (and not only low down) and hence the acceleration rate. Others have discovered a SBC offers greater low RPM torque, and also improves tale off. Am not familiar with the 944 S2 torque curve but reasonably assume it is greater than the 2.5 NA and a good deal more than a 2.0L. Sure that you won`t be too disappointed with the auto behind Dave. Between you and me, the later 944 trannies are the strongest and most desirable. FYI they already have 5 friction plates in the forward clutch and the larger 5" drum that`s also used in Audi 5 pot turbos. A tranny cooler is integral with the radiator and obviously has all the necessary lines and fittings that the 924s don`t. If you haven`t already changed the ATF and filter, do so and prolong the life.
Before I bought this car with an auto I priced a manual trans conversion, around 2K at the wreckers. The more I drove it around in Sydney traffic and up and down the Pacific Highway to the North Coast (600 Km one way, 6 hours at night) the more comfortable it became. Only real limitation is the top speed but will still double the state maximum. Increased fuel consumption due to higher RPM suffers but probably not as much as my heavy right foot contributes anyway. I just love flooring it to kick down. First gear up to 60Kmh and second at 110, which is ideal both on suburban and country roads.
Another incentive to hang on to the slush box now, is that I own the world`s quickest 924 2L auto. An honour that every turbo and manual owner can only dream about and/or poor truckloads of money into.
| 924guy wrote: | | wow, i didnt know anything about "my grandpa, The Don" before this, THANKS! |
Me neither. Thought Warnie was the country`s best cricketer for scoring the most roots ever in one test match.
Performance gains eh?
First priority is reliability. Reliability with double the stock horse power. Double the stock torque actually, which results in the same thing at any specified RPM. Its torque that matters to a transmission, that`s what they do, convert torque and alter RPM accordingly. With an auto there is the TORQUE CONVERTER that has a 2.5:1 ratio, that`s constantly variable feeding into 3 constantly meshed gears that are both selected and changed by hydraulic pressure.
The hydraulic system pressure has been increased. This applies more pressure to rubber lipped pistons that force the multiplate clutches together. Greater torque handling capacity before slipping. Also more pressure holding the band tight on the drum during second gear.
I`ve also modified the centrifugal weights in the governor to raise the shift point. Will post more details with data logs at a later date. It`s rather trial and error this process of machining down weights. Talking fractions of a gram here, and proceeding cautiously. Aiming for around 4-500 RPM more than the stock 5800. Have gained 1-200 RPM by removing 1.4 gms. Fortunately the governor can be removed externally from the trans by dropping the mounts and tilting it.
Picture time. Yeah.
Transaxle Engineering use the same VW 087 transmission in 700HP sand rails. Can you see that it is the diff section in our transaxles that is the weakest link?
After some experimentation and changes they have selected the same oil flow locations for the cooler as Porsche, and myself. That is the return line from the torque converter. Most heat is created in the TC when it is working, like converting torque during a standing start or climbing hills at varied speeds / loads.
This $4 part is a common OE problem. It is the forward clutch diaphragm spring, works on the same principle as a standard single plate clutch. Broke one about 5 years ago that resulted in this tranny`s first basic rebuild.
Activated by this piston that has a steel body with vulcanized rubber lip seals.
After losing all forward drive in this tranny I had expected to find another broken clutch spring or stripped/ damaged friction plates. All looked and measured so good that many dodgy rebuilders would not even have bothered to spend $100 on a rebuild kit containing new clutch plates. It could have gone back together with all the old parts.
Test your diagnostic skills here and help me guess the cause:
_________________
World`s quickest 924 2L slushbox
| Allan @ DTA wrote: | | I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards |
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ic932
Joined: 11 Feb 2005
Posts: 1104
Location: UK
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| Posted: Fri Oct 15, 2010 6:29 am Post subject: |
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Well the hand on the wifes leg is all to true as it happens lol. What I miss the most in an auto is braking though. I like to use the brakes in conjuction with clutch release ect... When you get it just right it just feels good. It might be my imagination but I'm always more cautious about locking up in my auto (bmw e30).
I put a brand new clutch in my S2 and it slipped slightly at the redline in 5th for the first 1K, this almost boost like quailty at the redline makes me wonder how that 3 speed willl cope.
I'm gonna give it a go anyway, the box itself is a so called re-built unit, theres a bill to prove it but I had a look underneath and its been painted silver with a black filter panel....probably just a known good one with a paint job lol. Still nothing to lose as they say...
I'll keep you informed as to its behaviour... for testing purposes how important is it to hook up the cooler lines? Could i just create a short loop and bypass a cooler? Don't want to install those cooler lines and rad at this stage. |
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Arvidw
Joined: 20 Sep 2009
Posts: 227
Location: The Nederlands (Europe)
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| Posted: Fri Oct 15, 2010 7:06 am Post subject: |
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Very cool modification, thanks for sharing 
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Porsche 924 2.0 Kompressor 136.1wHp @ 5650rpm / 201.9wNm @ 3900rpm (dyno @ dp-engineering.nl) |
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Scorpio
Joined: 05 Jul 2007
Posts: 1957
Location: Brisbane, Australia
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| Posted: Fri Oct 15, 2010 9:37 am Post subject: |
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You're a little bit crazy, but all the great one are! Nice work rc
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1979 NA
MS1..EFI..
GARRETT T25 TURBO
BILSTEIN SHOCKS
GT BASED CUSTOM BODYKIT
Brisbane , Australia
Think mean think fast
all youll see is
my Porsches Arse!!! |
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RC
Joined: 25 Mar 2007
Posts: 2636
Location: Australia
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| Posted: Fri Oct 15, 2010 2:11 pm Post subject: |
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| ic932 wrote: | | Well the hand on the wifes leg is all to true as it happens lol. What I miss the most in an auto is braking though. |
Ha, thought so, know where I`d prefer to put my hand and guess most guys feel the same way.
Agree you don`t get the same engine braking as a direct connection. Not a problem in most city driving or cruising but often select 2nd or sometimes 1st when descending hills or mountains.
| ic932 wrote: | | I put a brand new clutch in my S2 and it slipped slightly at the redline in 5th for the first 1K, this almost boost like quailty at the redline makes me wonder how that 3 speed willl cope. |
Well I have boost at redline and since the engine produces less torque than at midrange and there is also less load when the vehicle is moving, there is no problem here really. There is a hell of a lot more load and torque dissipated by dropping the clutch in a manual at 3 or 4K. Remember the torque converter engages relatively slowly, provides slip and torque multiplication from the stall speed. Depends on M/Y but around 2 - 2.5K in a stock car, the later 944 TC stall is quite low, 2K IIRC, as the engine has more low down torque. Stall speed varies with the engine power output. I am running a custom modified TC with a 3 - 3.3K stall, that was a big improvement (for acceleration) with the NA. Now it`s blown it has so much torque it spins the wheels easily if I floor it at the lights. In fact I loose an average 1/2 second in 0-60 time due to wheelspin. Hopefully the sticky 255s I just got will give more traction off the line. Seriously considering reverting back to a lower stall stock converter @ 2.5K though.
During the rebuild I tested the torque holding capacity of the forward clutch. Chucked the housing in the lathe and locked the spindle. Made an adapter to my torque wrench and applied force. Clutch held no worries at 240 ft/lbs, the max on this tool. That`s double the 2.0 NA torque and still lots more than a S2. In fact with a 2' pipe I was hanging off it with all my weight, 85 - 90 KG x 2.2 x 2 = just under 400 foot pounds. Not sure of the max TQ of an Audi 2.2 turbo but these boxes handle that OK anyway, same guts in the later 944 boxes.
| ic932 wrote: | | I'm gonna give it a go anyway, the box itself is a so called re-built unit, theres a bill to prove it but I had a look underneath and its been painted silver with a black filter panel....probably just a known good one with a paint job lol. Still nothing to lose as they say... |
An excellent start anyway. The filters and pan gasket are dirt cheap (if you don`t buy from Porsche) so do a change anyway. Change the fluid also and see what comes out. Only other thing to service is the 2nd gear band adjustment. Piece of cake, only need a torque wrench (accurate at low readings, 7 ft/lbs IIRC), a 17mm spanner and a 5 or 6mm allen key.
| ic932 wrote: | | for testing purposes how important is it to hook up the cooler lines? Could i just create a short loop and bypass a cooler? Don't want to install those cooler lines and rad at this stage. |
No drama at all. I haven`t fitted my cooler yet either and am just using a short loop too. The more heat the faster the tranny wears, so as long as you don`t try multiple stall speed tests or drive up the Alps you have ample time. The A/T radiators have cooler fittings while manual ones don`t. A rad cooler helps warm up but IMO does not dissipate sufficient heat due to the lower temp differential at 80* or so. Am mounting a conventional multiplate oil/trans cooler under the car in a higher air flow area below the stock accumulator position. Also intend to fit a VDO temp sender, same as for engine oil, so can either switch between eng/trans on gauge and also datalog the temperature along with all other engine parameters. Pix to come later.
| Scorpio wrote: | | You're a little bit crazy, but all the great one are! Nice work rc |
Cheers Scorpio. I`ve seen and read about your work and you also fall into the same category. How about more body work pix, especially of your crazy scoop.
We`re all freaks here, anyone who spends their money or time on a 924 must be BONKERS!
_________________
World`s quickest 924 2L slushbox
| Allan @ DTA wrote: | | I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards |
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morghen
Joined: 21 Jan 2005
Posts: 8883
Location: Romania
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gegge
Joined: 27 Jul 2007
Posts: 1124
Location: Sweden
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| Posted: Fri Oct 15, 2010 6:41 pm Post subject: |
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It is totally crazy but very impressive
I have just read about a budget low-tech highboost 2 litre pushrod Volvo B20 with an auto tranny in a Vega: 10.81 sek/207 km/h on the 1/4 mile. In version 4.2 he is adding compound turbo running on methanol
...it makes you reconsider the old slushbox!
This was the previous manual B20 Volvo 140: http://www.youtube.com/watch?v=fqzDCkZh7fM&NR=1
The B20 auto Vega: http://www.youtube.com/watch?v=CXiZPOzsuG4
The Vega at 2:28 http://www.youtube.com/watch?v=kDfYKMoheWc
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Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs
Last edited by gegge on Fri Oct 15, 2010 6:46 pm; edited 1 time in total |
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Rich H
Joined: 10 Jun 2007
Posts: 2665
Location: Preston, Lancs, UK
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| Posted: Fri Oct 15, 2010 6:42 pm Post subject: |
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Nice work.
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec |
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ic932
Joined: 11 Feb 2005
Posts: 1104
Location: UK
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| Posted: Sun Oct 17, 2010 11:49 pm Post subject: |
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Hmmm, I forgot about the 60-2 flywheel teeth on these 16V lumps  |
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RC
Joined: 25 Mar 2007
Posts: 2636
Location: Australia
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| Posted: Tue Oct 19, 2010 1:06 am Post subject: |
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@ Gegge, cool vids and one cool, or is that hot, POS Volvo. Even is registered, would surely make jaws drop at the traffic lights 60' dash or 1/8 mile.
Like that green 9 sec dub. WTF is in that? Fibreglass body probably on a funnycar chassis, but still a rear mount. Porsche perhaps?
Have seriously thought that these are ideal for a 1/4 mile car. I`m running 3.36:1 final drive and would have liked to fit the Euro 3.08 gears for the street/ highway. However the US ones have 3.55 gears that would be ideal. Only done a few 1/4 mile runs a while ago when less tuned and pulled a best 14.2 @101MPH with lots of wheelspin. Now have 3-4 PSI more boost. So tempting to fit 3.55s, nitrous and slicks.
| ic932 wrote: | | Hmmm, I forgot about the 60-2 flywheel teeth on these 16V lumps |
Know virtually nothing about the 16Vs Dave. Need the flywheel for the sensors eh? The 944 88 PET lists 3 or 4 flywheels, including the auto version, that would have to be a thin drive plate. Would also have to have the teeth inserts for the sensors. These 087 slushpuppies were used up to 88 IIRC.
Suppose it`s always possible to mount a 60 tooth wheel at the front crank for a signal, or a full programmable aftermarket ECU. Might be better though to strip the box and sell me the good bits. 
_________________
World`s quickest 924 2L slushbox
| Allan @ DTA wrote: | | I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards |
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