Well, I have a 78 corvette, and my reverse went out of it a couple months back. Finally got to take it out this morning and after taking it to my friends shop to have it looked at this is the information he gave me....

It's a Saginaw, its junk. And this occurrence will continue to happen as long as it's what I have in the car. Apparently the whole lower spline is all one piece and amongst that, the rest of the gears are all pretty well chewed up. Due to this, he says parts will be between $700-$900, then another $300 in labor(upwards of $500 at any other shop).

Now, The motor is a stock rebuild right now. He knows my plans are to put a little bigger cam, new intake and carb, and ignition system on it over winter to wake it up and make it a little healthier. Knowing this, he highly suggests not putting a Saginaw back in. He suggested I go to Summit Racing and purchase a brand new Richmond SuperT10 for $1700 and put in it. He says my clutch and bellhousing will all stay the same. He says this will never give me a problem and will hold up to a more healthier motor.

NOW, to my questions. If anyone has done something similar or had similar issues. What transmission did you use? Was the stand alone,reverse locking, stock shifter linkage able to be used, or is the new T10 transmission mounted shifter a direct fit? Money isn't a concern, doing it right however is. And I want a straight replacement, no console modification or anything like that. All information and opinions is helpful at this point!!

RYAN,

 

Autogear 4 speed.

This is my new M22W. Steel mid plate. It can take a lot of abuse.



I got mine from here, http://www.wrightconnection.net/trans-muncie.php but there are several vendors that build Autogear transmissions. The M20 is under $2K

My rebuild quotes were almost the same as a complete new transmission.

 

I just converted my 78 auto to a 4 speed with a Richmond Super T-10 from Summit.

Also rebuilt motor with forged crank, h section rods, flat top forged aluminum pistons, comp cams 274h cam, 750 cfm quadrajet from Summit, re-curved distributor, new intake, etc... And car runs great so far.

Only 300 miles on rebuilt motor and new Richmond box, but so far so good.

 

The tranny in my 80 is a stock Warner, it's a wide ratio with a 2:88 to 1 first gear. It's an aluminum case and I think yours was a cast iron case?
I believe it's the same tranny used in a 79 just upgraded, so it should fit, but I am not positive. The 80 has a bolt in tranny support. You would need at least the correct shifter with the linkage bars, reverse light switch bracket and switch. I've have a 383 since last fall and haven't broken the tranny yet, either has my son (he's better at spinning the tires than me). But, the stock rear is either the 3.07 or 3.08 and I would like to move to something like a 3.55/3.73 gears. Moving to different gears, the Warner will rev high on the open road. So, a 5 speed is a better tranny with those gears! What you really need is a plan for were you want to be with it. The Warner will work for now, but you speak of upgrades, so now it starts to get more involved.

 

No money worries ? Get the Tremec TKO 600 w/ .64 OD, vendors sell them so they fit right in to a C3.
If I am not mistaken the Richmond 5 speed is not an OD transmission. I get over 20mpg on the highway with my TKO 600

 

I would call silver sport transmission and get a new 5 speed. you'll be very happy with it.

 

The Saginaw was used with the L-48 in some 78-79 Corvettes. L-82's, and some L-48's, came with the better Super T-10. The Super T-10 was used in all other 75-77 and 81 4 speed Corvettes.

I'm not overly familiar with the Richmond Super T-10, but the Saginaw and OEM Super T-10, both used the same crossmember mounted shifter.

As others have said, an overdrive 5 or 6 speed, is a great way to go, though also a bit more expensive. There are also plenty of used original Super T-10's floating around.

 

the Borg Warner Super T-10 and the Richmond Super T-10 are basically the same trans, they are now ( and for a while now) made by Richmond Gear.

 

PM sent to OP...

 

Interesting! I looked and the final 5th gear is 1.0. But the first gear is 3.28 and may work with 3.08 rear? Also, the Richmond doesn't come with the shifter, but the Tremec does? With the Richmond, it's a tight ratio, lots of shifting. The Tremec's are wide ratio, better around town. Lots of factors, I guess the OP needs to think about what he wants.

 

I have a Richmond Super T10 with a Hurst shifter in my '78 L82. No compliants at all.

 

My L48 came with a BW super t10. I replaced it with a close radio Richmond super t10, and it was a direct replacement.

 

If you can even find those parts. The Saginaw used a 10.5" clutch and mated to the 168 tooth flywheel. The B/Ws used an 11.0" clutch with the 168 flywheel. Two sets of holes were drilled to accommodate both configurations. While using the less expensive Saginaw, GM was still able to use the same flywheel/starter configuration without the need for new parts for the L48/M20 setup.

Another oddball part was the use of the 10-spline input shaft typically used in th 1960s with four-speeds. In the 1970's four-speeds used a 26-spline shaft. So this makes me curious how rushell made his application work unless he used the 10.5 clutch setup. Sounds a like a previous made the switch.

I have corresponded with many a Saginaw owner frustrated with the inability to locate replacement parts whether it be clutch, shift linkage or some internal part. Under the circumstances...sounds like you're on the right path.

 

Short answer. A super T10 will hold up to the mods you'll be making. Shop around and be sure to check shipping costs. Places like SDparts and Pace can have better deals than Summit, etc.
The autogear Muncie is a nice upgrade but probably not needed for a mild engine.
As pointed out, you'll probably be changing your flywheel clutch. The new T10s are only available in 26 spline. They are available with 4 different ratios, with 1st gear from 3.42:1 to 2.2:1. The best choice will depend on your rear end ratio and what you'll use the car for.
The saginaw shift rods might be able to be modded to work on the T10, but I would suggest the tailhousing mounted hurst shifter. You'll also need to rig your reverse switch on the trans.