catfishjack

I have a 1979 L 82 4 speed. Can someone tell me the type of transmission Currently in the car, Borg-Warner?
and the gear ratio as I would like to get a new one from Richmond Gear but am not sure what to order?
All info appreciated. Thanks

KenSny

Yes, It's a BW and with the L82 it could have been the M20 (wide ratio) or the M21 (close ratio). Look at the codes on the tranny case.

MikeC

I have heard that 500 rpm between gears is a close ratio and a wide ratio has a larger rpm drop from 3-4.
Maybe someone will stumble onto this thread and confirm or deny what I just said.

PRNDL

I think.... let me rephrase that, I THINK the change in rpm will depend on your speed because we are dealing with ratios. 4th gear is 1:1, so if you downshift to 3rd keeping road speed constant obviously your rpm will increase. If you have the M20 wide ratio you likely have a 1.46:1 3rd gear, so if you are putt-putting along at 2000 rpm in 4th, your rpm will jump to 2920 in 3rd. M21 close ratio with a 1.28:1 3rd gear will jump from 2000 in 4th to 2560 in 3rd, which is close to your guess. But if you are cruising at 3500 rpm in 4th, the M21 will jump to 4480 rpm when you downshift into 3rd keeping your road speed constant.

i think! :)

MJ


[Modified by MNJack, 7:49 PM 1/21/2002]

VegasJen

catfishjack, my corvette black book shows only one listing for a 4-speed transmission option in '79. i do not believe that muncies were even still in production at that time. i thought that muncie production ended in the early/mid '70s and the switch to the borg warner was the next step. if yours is indeed a borg warner, you should be able to identify it as such by looking on the passenger side of the transmission underneath the car. above the centerline of the transmission it will have among other cast in characters: W G DIV which, of course stands for Warner Gear Division indicating without a doubt that it is a borg warner. as we all know, borg warners are no longer in production by warner gear so you have to go to richmond gear for replacement parts. if yours is a B/W, it will most likely be the "super t-10" which had a host of "improvements" over the earlier variations. the easiest way to tell if it is would be to count the number of splines on the input shaft. if you have ever replaced the clutch and still have the alignment tool, that would work as well. the "regular" t-10 had a ten spline input shaft like the saginaws and, i believe, the muncies. the "super" variety had the 26 spline input. if you know it's the original tranny and confirm it's a B/W, then you can pretty much assume it's a super t-10.
unless the factory changed the gearing in the 4-speed cars between '79 and '81 yours should be 2.88-1st, 1.74-2nd, 1.33-3rd, 1.00-4th. i know, because i just rebuilt mine in november. BTW, if your going to replace the entire tranny, go with the richmond five.
if i remember right corvettemagazine.com had an article when they first started about identifying the different 4-speeds and you can get more information on the super t-10 (now the richmond t-10) at richmondgear.com :chevy

Allan71

The Black Book usually only shows OPTIONS, which means that the standard equipment including engine and tranny is not often shown. Actually, there were 3 different manual trannys used in 1979. RPO M20 when used with the L48 was a Saginaw with ratios of 2.85, 2.02, 1.35 and 1.00 to 1. It was only used in 1978 and 1979 and was the only manual tranny available with the L48. RPO M20 when used with the L82 was a Warner T10, and had ratios of 2.64, 1.75, 1.34 and 1.00 to 1. This was the same Wide Ratio tranny that replaced the Muncie in mid-74 when the Muncies were phased out. The M21 in 79 was another Warner, with ratios of 2.43, 1.61, 1.23 and 1.00 to 1 and this was the same Close Ratio tranny that had also been used since mid-74. The RPO M18 used in 80 and 81 had ratios of 2.88, 1.91, 1.33 and 1.00 to 1. It's not as easy to use the 4th to 3rd gear trick on the Warner as it is with the Muncie, becasue the Muncie M20 has that huge spread between 3rd and 4th (1.46 to 1.00) compared to the Muncie M21 (1.28 to 1.00). The Warner spread between the two trannys is much closer; (M20 1.34 to 1.00 vs 1.23 to 1.00 for the M21). I was thinking it might be easier just to run the numbers in first gear. With the stock 3.70 axle with the M20, running 30mph in 1st should be about 3600 rpm, and with the M21 about 3300.

Paul L

The Black Book info does come up somewhat short in this area. In 1979 there were 8,291 M20s and 4,062 close-ratio M21s (the latter only available with the L-82). Four-speed manual transmissions used in all 1978-1981 Corvettes are Borg-Warner's Super T-10 units.

In the production code, the first letter is "W" to indicate Borg-Warner. The next letter indicates the month of production, with "A" representing January, "B" representing February, and so on to "L" representing December. The month codes are followed by one or two numbers denoting the day. Next comes a single number to indicate the year. And finally the last number indicates whether the transmission is a close- or wide-ratio unit. For example, a code of "WG2791" translates to a Borg-Warner four-speed, built on July 27, 1979. The final "1" indicates that it is a wide-ratio unit.

Ref: Richard Prince, "Corvette Restoration Guide-1968-1982." p. 223. MBI Publishing, ISBN 0-7603-0657-5.

Paul L

Allan,
You beat me to the punch!

VegasJen

interesting info, guys. i haven't committed to memory all the ins and outs yet but i'm learning! it's a slow day on the forum when i only learn one new thing! :cheers:

Allan71

Hey Paul, that's good info on the Warner codes. I don'thave Prince's book.

Does he give the code for the close ratio? Wonder if it could be a 2?