Trans conversion, from auto to man

stick1975 · 12-02-2008, 11:01 AM

I have an 82 928 with an 3 speed auto trans. and I want to change it to 5 speed man. Looked like this would be the place to ask.

Danglerb · 12-02-2008, 11:30 AM

Depending on how you do it, $5k to $8k, or buy a parts donor car and pull it all yourself.

Parts list (off the top of my head)

Tranny, ideally a rebuilt 85+ with better syncros.
Torque tube to match, again ideally rebuilt.
Clutch, ideally a rebuilt 80 to 86
Flywheel for manual.
Clutch master and slave, hoses etc.
Brake and clutch pedals.
Firewall bracket for clutch.
5 spd instrument cluster.

Unless you have a really special car generally you are MUCH better off to buy another with a 5 spd already in it. Converted cars don't get the same bump in value as factory 5 spds either.

stick1975 · 12-02-2008, 12:08 PM

Thanks for the info. I bought this car with a broken timing belt, and disassembled so I'm not so much worried about resale. I know this may make some of you sick, but I would also like to put a 6.0 liter LS1 motor in it. I just would not be happy with the 3 speed auto.

MPDano · MPDano's Garage

Quote:

Originally Posted by stick1975

Thanks for the info. I bought this car with a broken timing belt, and disassembled so I'm not so much worried about resale. I know this may make some of you sick, but I would also like to put a 6.0 liter LS1 motor in it. I just would not be happy with the 3 speed auto.

Doesn't make feel ill at all. Go for it!

Danglerb · 12-02-2008, 02:15 PM

The place with conversion info is http://www.porschehybrids.com/php/ I'm there with same name.

Drop in a Chevy eh?

I don't recommend a 5 spd at all in that case, it won't handle the torque for long. Much better option is to beef up a 4 spd auto from a newer 928 with AMG/Mercedes parts.

Unless your 82 is a Euro S its non interference, broken timing belt just means new water pump (what likely broke the belt) and a new belt. No need to pull the heads or anything else internal. As little as $200 in parts, maybe $600 if everything related is replaced, compared to about $12k to make Chevy power a reliable daily driver.

What do you plan to use the car for?

What state are you in?

stick1975 · 12-03-2008, 10:39 AM

Well I just want a quick street car. I already have the 6.0, and I know I can install GM per parts L92 heads ($1200 complete), intake ($300), hyd roller cam ($300), MSD ing controller ($300). Headers and all I think I can have the motor ready to set in for less than $4000. That would be 550 hp and with a good wide street power band on pump gas. I don't know how much more I would need with the Renegade kit that's around $2000, but I think I could complete the swap for well under $10,000, and almost have ZR-1 Corvette performance. Don't get me wrong, I like the 928 motor, hell I have another 1984 928 4spd auto car that I r&r the heads and timing belt, and water pump. I don't think I can fix the other car and make as much power as I can with LS motor without boost. I looked at the twin turbo 928. It looks like a work of art to me. Don't think I have seen many cars taken to that level. That's why I'm here, maybe I can learn something.

stick1975 · 12-03-2008, 11:09 AM

I'm in GA. Has anyone thought about trying to use a trans axle out of a C7 Corvette? Might be the hot setup for some of the 600 hp super cars I've seen on here.

Danglerb · 12-03-2008, 12:31 PM

Vette tranny has been kicked around, but it doesn't have the right dimensions for the place it needs to go without some serious cutting, and then I think there are still issues with input and output shaft locations. The 4 spd auto is a tank, and plenty of torque and HP usually gloss over all its weak points.

If you already have a motor, then around $10k might be right for the conversion. Lots of little $300 to $500 bits creep in, and many stages are pay for expertise or fab it yourself. After the conversion you still have most of the usual expenses of keeping a 26 year old 928 running well.

The catch with 550 hp is that you won't be able to put more than about 400 to the ground below 100 mph. In my book tires spinning from 350 hp are about the same as tires spinning from 1000 hp. On the drag strip where sticky tires can hook up, expensive things will break. One of the local guys breaks a lot axles, but decided he can't afford what might break if he made the axles stronger.

I'm still kicking it around, so don't take me as all negative, its just more expensive than it looks outside of the water.

stick1975 · 12-04-2008, 05:53 AM

Yea, I can see how the little things could add up quick. I know you said the 4spd auto is a good trans, what about the 3 spd auto? I might put the motor in then up grade to the 4 spd. Does Mrec. make the three spd auto too? Does the 3 spd or the 4 spd have a lock-up converter? Nobody around here really knows much about these cars in area. Guess this is the cost of trying not to be a belly-button Camaro or Mustang.

stick1975 · 12-04-2008, 06:10 AM

Is the V8 Porsche motor worth anything? All I know about is the timing belt was broken when I bought it. Most of the covers and componets were in the back of the car. The car come from Fla. Looks like it had a rough life. Thought maybe somebody on the east cost might see this and have a use for it. I know it can't be worth much. Just thought I would put that out there.

Danglerb · 12-04-2008, 07:51 AM

Both auto boxes are MB, with a Porsche designed differential tacked on. Starting with the 3 spd and switching as needed to the 4 spd should work. The catch with any transmission choice is whether or not you take a chance with a used vs rebuilding. An early 5 spd is cheap, like $600 used, but almost always will need a rebuild. 85+ 5 spd is more like $1500, but may not need a rebuild, or as much replaced. Used 3 and 4 spd auto boxes often less than $500 (they are more common and rarely break), but $2k easy for a rebuild.

Did you ever follow the link I gave you, LOTS of the conversion guys are in the SE, but NONE of them post here. Most of the swaps are with cheaper 944's, but still plenty of 928 guys.

Stock running US 82 motor is worth maybe $500 (hint hint, $500 and you could drop in a working motor and drive it now). Half a dozen of parts will still be worth $50 to $100, heads, cams, intake, distributor, oil pan, rest scrap mostly.

OTOH it may not have a stock, US, or 82 motor, so best to check the motor ID, and/or post some pictures. Motor ID is on the top of the front of the block. Look straight down just to the right of the passenger side radiator hose and you should see M28/ xx xxxxxx and those xx are what tells what it is.

stick1975 · 12-04-2008, 09:24 AM

Thanks for the info. Yes, I went to the link. Saw allot of sharks there. Read allot on the trans axle swaps, even seen my vette question mentioned. I'm kind of new to this whole "on-line" thing. I try to sit back, listen and learn. I might try posting some questions on that other link you showed me. I liked looking at the pics, some wild stuff on there. Have allot of respect for the builder's who aren't scared to try stuff like that, and make it work. Did you have any pics on there? Like I said, I'm new to the whole on-line thing, don't know what I'm looking at half the time.

Danglerb · 12-04-2008, 09:46 AM

Make a few posts and maybe you can hook up with somebody local for a ride. That can be VERY eye opening.

Two years ago I was planning on a conversion, then visited Renegade in Las Vegas, and the more I dug into it, the more it looked like it was going to cost. The killer is that I live in Calif and the smog inspection for an engine swap is extremely strict, which typically means it takes several attempts with fixes in between before a car that seemed "perfect" will actually pass, and that costs a bunch. Now that I have worked on my 928 and others for a couple years I think I am getting a clearer picture of what I might do and how, but so far it seems much cheaper to keep a Porsche engine for the performance level that suits me.

stick1975 · 12-04-2008, 10:17 AM

Well, I live back in the woods here in GA. My county has no emissions laws. I know they can be a real pain. If we did, I would just have to move. The only thing I got that would pass would be my daily driver 1500 Silverado. When you put a timing belt on the 928 engines did buy one of those high price gages to set the tension? Since I did my on my 84 928 I have not run it much at all. I've put timing belts on Honda's, Toyota's, Subaru's, and a bunch of other things, but I know read on Aldatta that it was a "must". I do not like the set up. I R&R the heads, timing belt and water pump because the car came in a shop I worked at with a tank busted on the rad. with no coolant. I replaced just the rad. and did a CO test on the cooling sys. and combustion was getting in. Not long after that, I bought it.

Danglerb · 12-04-2008, 05:08 PM

Most people just use the Kempf tool, about $60 new plus shipping from all the usual vendors.
http://www.928gt.com/ps-35-68-tool-9131--timing-belt-tensioner-tool.aspx

My personal technique for putting on a timing belt is to say, "Greg put timing belt on that one." Not at all my plan, but the damn thing broke when I absolutely had no time to fix it myself. When I put my next motor together pretty sure I will do it myself, but can't say for sure if I will use my Kempf tool or borrow the "real" Porsche gauge. If I can I will try both.

I think the main reason timing belts fail is improper tensioning, and it may not show up for some time later.

Xlot · 12-04-2008, 05:32 PM

Quote:

Originally Posted by stick1975

I have an 82 928 with an 3 speed auto trans. and I want to change it to 5 speed man. Looked like this would be the place to ask.

Here's a link to auto-to-manual conversion.. of a RHD car, but no drive-train differences other than which side of the car the pedals go

http://www.landsharkoz.com/tech/stu/conversion.htm

Includes parts list, photos etc.

stick1975 · 12-05-2008, 08:38 AM

I appreciate the info. Good link. Showed me allot of things that I didn't know... Maybe rethink my swap, or try and find a good donor car. Looks like it takes more than just pedals, trans, and a clutch! Nothing like the the F-bodies I've done.

Danglerb · 12-05-2008, 09:41 AM

Nice cars with with any trans type you like show up with bad motors often enough there just isn't any point in starting with less.

stick1975 · 12-05-2008, 10:17 AM

Maybe. I have not seen many cars reasonable around here. I bought the 82 928 as a parts car for the 84 928 because it was dirt cheap. It had some kind of 17 in wheels on it that looked good too, but the interior was trashed and the front of the motor was in the back. I've had both cars for like 7 years and just not had time to mess with them. I know its a buyer's market right now, so I was just looking and dreaming. Still want a 5 spd though.