I'm buying a 68 Sprint. It currently has a 3-speed manual. I believe this is a Saginaw gear box. I want to install a Muncie 4-speed. I'm hoping the Muncie will slide right into the bellhousing, fork arm, clutch and flywheel. Is this the case? I realize a new throw out bearing may be necessary as well as warranted. The drive shaft may need altering or replacing too. Other than this, is this swap a bolt in? Thanks.
Someone else can chime in, but I think it is a simple swap. Unbolt the Sag and bolt in the Muncie. You shouldn't even have to touch the throwout bearing or anything in the clutch unless you want to. The driveshaft should work fine. You obviously need to have a 4 sp shifter.
An original sprint six would be floor shift not column so that part is easy. the hole in the bellhousing may be smaller for the three speed bearing retainer and the Muncie may have the larger fine spline input shaft if it is a later one. the shifter and install kit are specific to first gen cars.
I'm still researching this SAG 3 to Muncie 4 swap. All indications are that it is a direct bolt in swap...with one possible exception. I found one source that says the SAG bearing retainer is 4 10/16" ø, while the Muncie is 4 11/16" ø. If this is right that ain't gonna work. The spines are the same at 1 1/8"ø 10/27 (earlier Muncies). The input shaft length match at 6½". The pilot diameters are .590". The pilot length is 1".
So Neill your warning is well taken. The bearing retainers have to be the same diameter. Maybe I have to find another bellhousing. I'll keep researching.
No, I don't know if the current 3-speed is a Saginaw or a Muncie. I'll find out for sure in a week or two. (Why? I take possession of the car in a week or so.)
A Saginaw 4-speed? No. Everything I've read advises not for performance applications. While the Sprint may not over power a Saginaw 4, I'm not entirely sure I'll keep the OHC 6. I want improvements to the car to be future proof. A Saginaw 4 won't hold up to an LS...the likely transplant.
If I do change the engine I'm in no hurry. Everything else about the car needs to be upgraded before installing a healthy modern V8.
I thought this site automatically censored foul language but it let LS through? If your going to put in a 'censored' engine why would you think about a muncie? Must be some trannys more suited to "future proof engines" than a 46 year old Muncie. A Tremec or similar. The overdrive itself is a good enough reason if you're going to swap trannys anyway, I like the TKO in my 68.
The Muncie is a fine transmission. It doesn't need to be the best. It only needs to work and a Muncie fills that bill nicely. It's what I grew up with as well. Overdrive would be nice and that is on my wish list. Instead of a transmission with just a single overdrive, I like the GearVendors under/overdrive unit. This unit provides an overdrive for each gear, not just the 1:1 gear. Essentially you have an 8-speed transmission though you would't be shifting through all 8 speeds all the time if ever at all. The GV is great for when you wish had something between gears. A modern transmission would be fine, but for somethings I want something a little different.
The Sprint engine is running fine, but the day will come when I want more. I'll hand the car over to the kids one day too. They may or may not be into working on cars. The Sprint engine will just get harder and harder to keep operating. If I didn't go with an LS, I'd go with a Chevy engine. I'm not partial to Pontiac. I just think the Firebird is far better looking than the Camaro. You'll always be able to get parts for a Chevy.