Saginaw 3spd to Super T-10 swap.

[Darwinskeeper]

It looks like I'll finally get back to working on Darwin again. Had been hoping to make a few changes for the past year or two but uncertainty about work and saving to build a garage has put upgrading the little red wagon on the back burner. With Boeing's USAF Tanker win, it looks like I'll have a job for a few years and I'll be able to get started with Dar in a few months. =P~

The general plan involves acquiring a Vortec5000 (L30) V8, installing a GM 14097395 Roller Camshaft (196/206 dur@.050; .431/.451 lift@valves; 109 lobe separation), dropping on an electric choke 750 Quadrajet, an Edelbrock Performer Vortec intake manifold, and a set of 1 1/2 primary full length headers.

I'm tempted to drop a Richmond Super T-10 with Z ratio gears (3.42, 2.28, 1.46, 1.00). My calculations have suggested that the Z ratios will work well with my current 2.41 gears, with 4th being a highway gear and 3rd being just low enough to handle around town work. My concern is that Richmond rates the Z ratio Super T-10 as being able to handle 286 lbft. The 305 may be anything but a power house, but I have estimated that it should be able to churn out about 300-350 lbft. Would the Z ratio Super T-10 be able to handle occasional clutch dumps and passes down the drag strip with 350 lbft and a set of 225/60R15 Radial T/As?

The other question involves the advisability of upgrading the 7.5in rear end with 28 spline axles, an aluminum rear end gurdle cover and a limited slip of some sort. My reading of the driveline forum has shown that there are quite a few 7.5s involved in fairly serious racing out there but most of them use automatics. Is it reasonable to reinforce a 7.5 (which has the advantage of being lighter and having 2.41 gears) to handle the abuse provided by a warmed up 305, a manual transmission and 225/60R15 tires? Is so what would you recommend?

Also, what would be my limited slip options?

 

[kevind]

I tried a 7.5 with a mild 406 and a Muncie in 94. I think I went through ten rearends that summer. They were all stock rearends. I think I broke one or two axles and a couple of posi units. The ring and pinion are the weak link hard shifts would break them. A 2.41 gear is going to be harder on transmisions than something like a 4.10 would be. The 7.5 will last if driven normal.

 

[Darwinskeeper]

Super T-10 swap?

I am looking to finally replace Darwin's aging 3 speed Saginaw. As nice as it would be to have 5 gears, I'm seriously thinking of a Richmond Super T-10. It would be the easiest to replace the Saginaw with as I could use the current clutch mechanism, bellhousing, and crossmember. I do have a couple of concerns.

My calculations suggest the Z ratio ST-10 box (3.42, 2.28, 1.46, 1.00) would be the best fit for my current car. With the 2.41 gears, 4th gear would be an overdrive while 3rd would have a 3.55 final drave ratio and be better for around town work. My concern is that Richmond rates the Z ratio ST-10 as being good for only 286 ftlb. I am planning to replace Darwin's six with a warmed over Vortec 5000 (L30 motor) which should be good for about 300-350 ftlb and am concerned that this little 305 will be too much for the ST-10.

Am I worrying too much about nothing? I don't plan to abuse the box too hard but I would like to occasionally burn rubber with the new engine and may hit a local drag strip for a test and tune night. There may also be a little power shifting (if I ever figure out what power shifting is ). The car currently uses 225/60R15 tires and future plans may call for smaller tires.

Also, would I be able to place the shift lever in the existing Saginaw 3 speed shifter hole in the floor or will I be forced to cut a new hole?

What do you think?

 

[t5montecarlo]

I contemplated a T10 in my wagon. I decided that putting the shifter through the original hole was not going to easy; the reverse lever on the T10 is where the shifter needs to be, so the hole will have to be moved rearward.

 

[kevind]

When I broke all the rearends in the 90's I never had any transmission problems. Napa's clutches were another story I got to where I could change one in 30 minutes. I'd say give it a try the rears will break before the transmission. I probably have some 2.41 gears I can sell You.

 

[Doober]

Well so far my 2.29 stock 7.5 has lasted 2 summers behind a Saginaw which has gearing very similar to the T10 you're looking at. Believe it or not you should be fine with 4th around town. The RPM range on the cam in the 350 I have in the Malibu is 1800-5600, which besides the 1405 Edelbrock & GMPP dual plane (no EGR) intake is a stock Vortec 350 short block, down to the rotating assembly (heads are Vortec, block/rotating assy. is from 1988). I can cruise through town in 4th at 35mph on 255/70/15 tires (~29" tall) without a single issue (~900rpm), I'm sure with a cam much milder than mine you'll have no problems at all in 4th, though it won't accelerate as easily Just remember when you get a flywheel you'll need a 153-tooth unit for a one-piece seal SBC. Late '80s F-Bodies are a good place to look. I believe they are using a different design flywheel now, can't really find the one I have anywhere, the newer style is apparently a lighter weight design from what I can tell.
http://www.oreillyauto.com/site/c/detail/SAC0/NFW1004.oap?keyword=flywheel&pt=02271&ppt=C0338

Far as a 305, personally I don't know if you'll see much of a MPG difference between it and a 350. The EBL I'm using has so far shown me getting pretty much the same MPG with the 383 I just built, 28" tires and 3.08s as I was with the 4.3 it had.

There are 4 posi/limited slip units that come to mind... the gov-lock type that (from what I've read) has kind of a bad reputation for breaking and is more for low traction situations (mud, snow, etc.), a clutch/cone-type unit that uses sprung pressure to keep both wheels turning, lockers that engage after some wheelspin (probably the strongest but I've read reports of some can lock up during freeway use and get a little hairy on wet surfaces), and the Detroit Trutrac units. The Trutrac is probably the one I would want to use because it supposedly has the smoothest operation. I think you could check the axles & see what shape they're in, and if they're ok simply install a support cover for now, unless you really want to upgrade the axles, in which case I would get the cover/carrier/axles and do it all at once.

 

[LS6 Tommy]

The Muncie is a stronger transmission than a the T10, but keep in mind, they run T10s in NASCAR with a LOT more tire & power. We ran a Texas Racing T10 in the GT1 car for years. Granted, you're not dumping the clutch in road racing...

Tommy

 

[Doober]

...and typically not on the street either I think a T10 will be just fine behind whatever you build. Judging from anything I usually read from you DK , you're not especially abusive on parts... that trans should have no problem holding up to your driving habits