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Gm 4 Speed

Discussion in 'Early CJ5 and CJ6 Tech' started by jeepstar, Nov 15, 2018.

  1. Nov 15, 2018
    jeepstar

    jeepstar Sponsor Sponsor

    Sheboygan
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    Last edited by a moderator: Nov 17, 2018
  2. Nov 15, 2018
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    It's a Saginaw 4spd. It was offered in passenger cars like novas, monzas...

    The desirable version has 3 rings cut into the input splines. They have the deepest first gear ratio, around 3.5:1 if I remember.

    I have had 2 of them behind v6s. I love them. They are smooth shifters with a great ratio spread. Some complain that the shifter comes out at an undesirable location, but it never bothered me.

    Advance Adapters still offers this adapter.
     
  3. Nov 15, 2018
    jeepstar

    jeepstar Sponsor Sponsor

    Sheboygan
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    so it could bolt up to any GM engine?

    also, the price on the sticker in his picture says 200 bucks.
     
  4. Nov 15, 2018
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    I will add this...
    One of mine lost (or never had?) its hardness on the Advance Adapters main shaft needle bearing surface. I had to tear it down every 10,000 miles or so and take the shaft to a machine shop to have them resurface it. PITA

    If you're going to check it out, pull the side cover and check for play where the main shaft joins the input shaft. I dunno if it was a common problem, or just mine. The other one I had was fine, but I didn't have that one nearly as long.

    I don't remember bearing retainer dimensions off the top of my head, but I'm thinking this should bolt in place behind a V6? Guys, correct me if I'm wrong. The Buick bell with the GM trans pattern is what you want. I can't remember clutch disc, throwout bearing or pilot bushing specs. I haven't owned one of these for close to 25 years.

    I'd only give that price if it's in perfect condition, has the three-ring input, and it comes with the shifter assembly. This setup is easy to nickel-and-dime you to death if it doesn't come with all the parts you need.

    Reselling it would be tough- it's a limited audience.

    This is the 3-ring input:
    [​IMG]
     
  5. Nov 15, 2018
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    Here's the gearing judging by the input shaft grooves:

    Saginaw 4-speed 1st 2nd 3rd 4th
    No lines (grooves) 2.84 2.01 1.35 1.00
    1 Line (groove ) 2.54 1.80 1.44 1.00
    2 Lines (grooves) 3.11 2.20 1.47 1.00
    3 Lines (grooves) 3.50 2.47 1.65 1.00
     
  6. Nov 15, 2018
    garage gnome

    garage gnome Rust polisher Sponsor

    Western MA
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    I have a Saginaw with the 3 rings. :D Bought years ago for a future unknown project. They are weak trannys. My buddy blew his up in a gasser with a mild 350. Muncie m21 or m22 is what you want. Also known as a rock crusher.
     
  7. Nov 15, 2018
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    The Muncie M's have terrible first gear ratios though. 2.56:1 was the best you could get. I ran one of them for a bit too, and I despised it. I felt like I was rowing through gears and not gaining any speed after I finally got moving in first. And Noisy! The aluminum case transmitted every little whine straight through it.

    The Saginaws are plenty strong behind a v-6. You'd have to beat the tar out of it to kill it in a stock jeep. They came from the factory behind many v8s. The 3-ring versions were mostly in 4-cyl Vegas.
     
  8. Nov 15, 2018
    Daryl

    Daryl Sponsor Sponsor

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    I wouldn't turn it down if it was free but certainly wouldn't pay anything for it. I have sold a couple GM 4 speeds this year, both to GM car guys that just wanted the transmission for parts. Sold both for $100 or less as there just isn't a market for these things anymore. As mentioned above, if you are over 5 foot 6 or 120 pounds the shifter really is horrible.
     
  9. Nov 15, 2018
    garage gnome

    garage gnome Rust polisher Sponsor

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    I would just go with a new tremec 5 speed if you want that style of transmission. Beefy and you get overdrive.
     
  10. Nov 15, 2018
    colojeepguy

    colojeepguy Colorado Springs Sponsor 2019 Sponsor

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    I'm sure that would be too long for a short wheelbase Jeep.
    I think a 4 speed with a 3.50 first would be nice for anything other than a hard core crawler (I've been 4wheeling with a 2.79 1st gear 3 speed for 20 years)
    If you get the shifter made for a Jeep conversion, it has a big dog leg in the stick do its not coming up under your right leg.
     
    ITLKSEZ likes this.
  11. Nov 15, 2018
    Keys5a

    Keys5a Sponsor Sponsor

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    I think the advertised transmission/adapter is for a small-hole D18. I'm not a huge fan of the Saginaw 4 speed. I've seen too many shuck all the teeth on the cluster gear from the input shaft mesh, and thats with 283's or 327's.
    A T10 or Muncie is much stronger, but they don't offer the lower 1st gears. I have Jeeps with both the beefier transmissions and never really needed lower 1st gears for my use, and the closer ratios work better in deep sand where most of my experience was.
    -Donny
     
  12. Nov 16, 2018
    nickmil

    nickmil In mothballs. Sponsor

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    Ive been running 3 groove Saginaw four speeds for 30 years in my '59-5. Trail running, Sand running, Search and Rescue, and racing. I was in Rescue at the Oregon National Dunes and ran paddle tires, Terra Tires, and trail tires. No issues. Behind a dyno'd 220hp Buick V-6 at the rear tires.

    I've rebuilt many of them and repaired many of them for myself and customers. There are certain things that need addressed with these when converting them to a Jeep transfer case.
    First is the vent. The stock Saginaw vents through the tailhousing. People convert but don't move the vent. What happens is the pressure builds up in the transmission as it warms up and forces the lubricant through the rear output bearing into the transfer case dropping the transmission level and overfilling the transfer case. A problem of the conversion and person doing it, not a design issue.
    Second is the drain on the stock transmission is the bottom tailhousing bolt. Remove it to drain the fluid for a change. When converted you cannot do this and yet people don't add a drain so the fluid cannot be properly changed. Again, a conversion/converter issue, not a design flaw.
    The blocking rings are smaller than on a Muncie M- series or Borg-Warner T-10 so will wear out faster under hard use. Some of this is due to lack of lube changes (see above) and some to being designed for less horsepower. Yes, substandard compared to the Muncies and BW-T-10's.
    The biggest weak point I've found is the 3-4 synchronizer hub. Under very hard use they will crack radially not allowing the 3-4 sleeve to shift back into 3rd gear. I've cracked 2 in this area in 30 years. I've never broken a gear in any of them but have worn out several. Typically second gear.
    Typically when the transmission breaks it's because the bearings have worn to a point the gears can spread apart and there isn't enough tooth contact between the gears and they shear. I've found this on T-90's, T-86's, T-14's, T-15's, etc.

    Muncies wear out the case bores for the counter gear shaft. The aluminum case gets elongated in this area due to thrust loads. I actually shattered an aluminum T-10 case and never broke a gear in the Race Jeep due to thrust and radial loads from the gears. I drove it back to camp and re-cased it with a cast steel case with new seals and all the same gears. Worked great for another racing season.

    The later Tremec's won't fit in an early CJ GarageNome. They are simply too long. In a Jeepster or CJ-6, no problem.

    Daryl, I'll give you $100 for every 3 groove Saginaw 4speed that has good gears inside.

    I doubt they are still available but at one time there were stronger gears available for the Saginaw 4 speed for short track stock car racing. That should say something.
    My biggest complaint about the 3 groove Saginaw is the jump from 1st gear to 2nd gear with 5.38 diff gears. Too big a jump but works great off road and a good compromise if you don't need a real deep first gear.
     
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  13. Nov 16, 2018
    colojeepguy

    colojeepguy Colorado Springs Sponsor 2019 Sponsor

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    Question for Nick or anyone else who has one, whats the length on one of these with the TC adapter?
     
  14. Nov 16, 2018
    Wmi68CJ5

    Wmi68CJ5 Let the Sun Shine!

    Twin Lake MI
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    I have one in my '71 '5 and I love it also. Very smooth and almost scary how fast you can run through the gears. Behind my v6 it makes for a very quick combo. Great info from Nickmil btw. If I remember correctly the adapter was made as thin as it is so this swap is a drop in with out drive shaft length changes. Correct me if I'm wrong Nick.

    Todd
     
  15. Nov 16, 2018
    wheelie

    wheelie beeg dummy Sponsor 2019 Sponsor

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    Yea, my '71 had a Saginaw in it when I bought it. Didn't know squat about this stuff back then. 3.73 axles and 33's. Didn't do any rock crawling back then but it worked okay on trails and was actually pretty nice around town. The shifter was long and kinda goofy but not hateful. I guess what I didn't like about it was the external shift linkage. Playing in the mud and the creeks and stuff gave me fear of crap getting crammed into the linkage. Never actually happened so my fears now seem unfounded.

    In short, I'd probably be fine with another one........ that Nick rebuilt for me. (y)
     
  16. Nov 16, 2018
    nickmil

    nickmil In mothballs. Sponsor

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    I can crawl under mine tomorrow and take a measurement if not raining. Very compact though.
     
  17. Nov 16, 2018
    nickmil

    nickmil In mothballs. Sponsor

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    Yeah, very thin. Depending on who produced the adapter and what generation between 3/4" and 1" thick. I went to studs instead of bolts as I was pulling the threads out of the adapters under racing conditions. It eliminated the problem altogether.
    The other issue I found is poor shifter mount design. It would put uneven pressure on the bolts and pull the threads out of the aluminum adapter. I had the same issue (my fault) until I properly spaced the mount. This also fixed the problem.
    The adapter was designed to mimic the Intermediate plate like used on Muncie's and T-10's. Actually a good design with minor upgrades.
     
  18. Nov 16, 2018
    nickmil

    nickmil In mothballs. Sponsor

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    Why thank you! :).
     
  19. Nov 17, 2018
    termin8ed

    termin8ed I didn't do it Staff Member Sponsor

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    I moved this thread to the tech section. Some good info here
     
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