I've got a 51'GMC 3/4 Ton with a chevy 235 and a saginaw 4 speed.Rear cross member is missing.I havn't driven this truck yet but the more I think about it, this can't be good.It's an older conversion 70's?/80's? I don't know,But I don't like the idea of the trans hanging off the bell housing with out support to the rear.Is this the way this is,or am I missing somthing. thanks Jimmy
The truck didn't have a tranny cross member when it had the GMC engine and stock tranny. It is supported by the bell housing mounts. I'm sure your 235 is mounted the same way.
You still have 3 mounting points, front and sides. There is nothing "can't be good" about it.
"It's just a phase. He'll grow out of it." Mama, 1964
Thats right Cletis! Just the front mount and the two on the bell housing.I've got a 53'chevy bell behind a 62'235 and it all fits good,but on the frame at about where the trans ends are some holes that look like they may have been for a cross member.
Up through '53 there was a transmission crossmember on 1/2-ton trucks. When the bellhousing crossmember design changed starting in '54 they discontinued the transmission crossmember.
That's on 1/2-ton trucks. I don't know about 3/4-ton trucks.
1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more... It's true. I really don't do anything but browse the Internet looking for trouble...
The "universal" crossmembers I've seen require welding after fit-up. My '65 C10 has no crossmember, except a light one for the e-brake. My old 3-speed tranny doesn't even have any holes or boss for mounting. The 4-speed is out of a '74 car...I had to mill off some of the rear mounting to clear the e-brake! My understanding is that if you use a cast iron bellhousing (as opposed to aluminum) you'll be OK for a manual trans. If you're mounting an automatic, you NEED a rear crossmember.
cm
If you can't fix it with a hammer and screwdriver, you need a bigger hammer. 1965 Chevy C10
What year(s) are you referring to regarding 3-speed and 4-speed manual transmission rear-mounts?
The frame cross-member at the rear of the transmissions was commonly removed from 1947-1953 trucks - for more convenient removal/installation of transmissions (especially the heavy 4-speed transmission). This is probably not a good thing, if the transmission rear mount served a good purpose?
From 1947-1953, ALL 1/2 ton Chevrolet trucks (and, I think all 47-53 GMC 1/2 ton trucks) came with a cross member at the rear of the transmission (and had a mount for the rear of the transmission). This was the case for 3-speed and 4-speed manual transmissions (and for the 4-speed Hydra-Matic transmission in a 1953 GMC 1/2 ton long-bed and short-bed).
I do not know about transmission rear-mounts for 3/4 ton and larger trucks.
In 1954, the 1/2 ton frame cross-member for the rear MOTOR-mounts changed. And, the clutch housing and rear MOTOR-mounts changed. This stronger mounting-arrangement from 1954 onwards resulted in no need for a manual-transmission rear mount (or for a frame cross-member for the TRANSMISSION rear-mount) - this was the case for both 3-speed and 4-speed manual transmissions (on the 1/2 ton - I do not know about the 3/4 ton).
In 1954, the new Hydra-Matic transmission (on a Chevrolet truck) was used with a frame that had two different cross-members than was used on other 1/2 ton 1954 frames: (1) the rear MOTOR-mount cross-member was different (different from earlier years and different for other 1954 1/2 frames); and, (2) a frame cross-member and a TRANSMISSION-mount were at the rear of the massive Hydra-Matic transmission.
I can only speak from my own experience with a '50 3100 4 speed. It did have a rear tranny cross member, but it also had a torque tube rear end that I believe was the basis for the rear cross member. In about 1978 I replaced the rear end with an open drive line and ditched the cross member. In 30 years I have not had any problems here. I will let you know if I do in the future.
I have a 53 3100. When I dragged it home it had the tranny cross member and the 3 speed on the column. The transmission was in the truck on the floor. The support plate was also in the truck but the rubber pad is gone. I am not sure if this is repairable or if I need to buy a new one. I am converting it to a 4 on the floor because that is what I want. And will keep the enclosed driveshaft.
So, I should use the cross member when I put the truck back together? Will I need to purchase a new support plate?
TIA
Dennis -there is nothing stronger than the heart of a volunteer-
All the 3800 AD trucks I've ever been under did not have a crossmember or rear trans mount. I'm inclined to think the rear mount might have more to do with the torque tube than the trans itself.
All the 3800 AD trucks I've ever been under did not have a crossmember or rear trans mount. I'm inclined to think the rear mount might have more to do with the torque tube than the trans itself.
I agree...neither my 3600 (3 speed) or my 3800 (4 speed) has a trans crossmember.
Most likely the stronger engine mount cross member made a rear transmission mount unnecessary in larger trucks. That cross member was beefed up in 1954 1/2 ton trucks.
here is a hydramatic out of a 55 that was behind a 235 and there was no facility for a rear mount http://yfrog.com/12dscn2074lj sorry forgot to add the link before ron
My 1951 3100 Chevy had the crossmember under the three speed.I modified it to fit my T-5.
My 1951 3100 Chevy suburban with 4 speed has the same crossmember .
1951 3100 Chevrolet 1951 Chevrolet Suburban Carryall Image "A house is built with boards and beams. A home is built with love and dreams." "Look deep before you leap !!!" / "Everything is Everything" "If I say a mouse can pull a house, hitch him up"
I just installed one on my ‘52 3100 which was missing. I bought one from Classic Parts, which to my surprise fit perfectly. One issue I had installing it was I needed to loosen the two rear motor mounts and jack the tranny up a little bit in order to get it to slide into place.
Phil Moderator, The Engine Shop, Interiors and Project Journals
1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube Updated to: ‘59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc Brakes Project Journals Stovebolt Gallery Forum
There has to be some type of torque tube ball housing support for 1953 and earlier manual transmission trucks with a torque tube (edited). The torque tube ball housing needs to fixed in place with the truck frame. Inside the ball housing, the inner ball swivels with the motion of the rear axle and the splined shaft coupling moves in-out direction also with the motion of the rear axle.
If you have an open driveshaft transmission/rear axle, you don't need the torque tube support if the rear engine mounts/support are capable (strong enough) to support the transmission weight. Being that the rear motor mount was improved in 1954, I would think 1953 and older trucks may benefit with a transmission support.
Last edited by buoymaker; 12/04/20208:31 PM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
In case someone only quickly reads your first sentence, you might want to edit it it to read:
"There has to be some type of torque tube ball housing support for 1953 and earlier manual transmission trucks with a torque tube."
For the sake of "completeness":
1954 trucks with the Hydra-Matic transmission that attached to a torque-tube have a rear transmission mount and two additional (and removable) frame cross members. The Hydra-Matic is a long and very heavy transmission.
The 47-55 1st. Factory Assembly Manual shows the second member 2296067 for 3100 with RPO 314 Automatic Transmission. The Master Parts List (7.011, Member, Frame Cross, Second) says 2296067 for 1954-55 with HT (7.011, Member, Frame Cross, Second). However Master Parts also lists another second member 1948-53, 1/2 ton, 3686848.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
Well, after spending some time looking at the Factory Assembly Manual and re-education myself to the proper terms for the cross members of an AD truck (yes I fell like a dummy) I have to start from scratch. For a 3100 there are 4 cross members. The front cross member, the rear engine support, the second cross member and the rear cross member. In my previous post I said the second cross member but that was wrong. I should have said the transmission support or even a propeller shaft support. Attached are examples collected from searching.
Last edited by buoymaker; 12/08/20209:06 PM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
Continuing, attached is a sales brochure and the part needed to extend the propeller shaft to make a 8 foot 1/2 ton truck. Except for propeller shafts with universal joints, I'm back to thinking that the torque tube (closed type propeller shaft) ball and slide type joint needs support of some kind.
Last edited by buoymaker; 12/08/20209:07 PM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
There has to be some type of torque tube ball housing support for 1953 and earlier manual transmission trucks with a torque tube (edited). The torque tube ball housing needs to fixed in place with the truck frame. Inside the ball housing, the inner ball swivels with the motion of the rear axle and the splined shaft coupling moves in-out direction also with the motion of the rear axle.
I think you said it all with that statement. The torque tube moves allot and creates allot of additional forces, all at the tail of the transmission. Without that support you would multiply those forces by the length of the tranny to the rear motor mounts. You only find the rear transmission crossmember on torque tubes so I think you hit the nail on the head!
Phil Moderator, The Engine Shop, Interiors and Project Journals
1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube Updated to: ‘59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc Brakes Project Journals Stovebolt Gallery Forum
Saginaw 4 speeds have a very rugged cast iron case- - - -you probably don't need a rear crossmember unless you just want it to be there for some reason. Even the aluminum case Muncie 4 speeds worked OK without a rear mount on some applications. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Saginaw 4 speeds have a very rugged cast iron case- - - -you probably don't need a rear crossmember unless you just want it to be there for some reason. Even the aluminum case Muncie 4 speeds worked OK without a rear mount on some applications. Jerry
Tim, I try to be accurate even to the point of "ad naseaum" because readers use this forum for reference. The picture above with the green engine is a 1954. It has the support, So to me it would be accurate to say 1954 1/2 ton trucks and earlier, with original 3 speed or 4 speed with torque-tube tail housings, have this support.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
