Transmission / Overdrive: Tremec T45RS 5 speed swap questions

[BShaw]

I finally carved out a day to start on the engine/tranny swap in my 60 Hawk. Pulled the 3spd OD and got the old 289 ready to come out tomorrow. Going in will be a full flow 289 and a Tremec T-45RS (a modified T45 from Keisler Engineering).

To accommodate the T-45RS my measuring tells me I will have to modify the doghouse and, more importantly, that big crossmember (the one that goes all the way across beneath the front seat).

My question is, can that cross member be removed and worked without screwing up everything? I don't see any way around modding it (for 1-1/4 or so additional bottom clearance) so what precautions/recommendations have you? Thanks.

[Carl Purdy]

I don't remove the cross member I just cut the bottom ring off. For a one piece drive shaft. After I get the drive shaft installed I jack up the rear so that one wheel is off the ground and then measure how far the drive shaft has came down add about a inch and make a U shaped loop and bolt or weld it in. I done my 51 that way back in 1985 and it still working fine. With over 90,000 miles since redone.

[Alan]

Let's see some pictures. I have a TKO 500 in my Avanti and I didn't have to modify the cross member, so it leaves me puzzled.

[Carl Purdy]

Now I am puzzled does the Avanti have a 2 piece drive shaft? I assumed he was talking about a 2 piece and going to a 1 piece.

[PackardV8]

I assumed he was talking about a 2 piece and going to a 1 piece.

In the first post, Bob mentions he has a '60 Hawk, which should be a one-piece driveshaft.

jack vines

[BShaw]

Let's see some pictures. I have a TKO 500 in my Avanti and I didn't have to modify the cross member, so it leaves me puzzled.

The crossmember I am referring to in my 60 Hawk is the big flat one that sits behind the bellhousing support crossmember. It's attached to the bottom each frame rail with 4 bolts and out by the ends at the rocker panels with one bolt. From SBCA96's Avanti/TKO how-to article it looks like the Avanti has an X-member instead of my straight-across member.

[sbca96]

You are refering to the crossmember that goes from A-pillar to A-pillar? I can
not imagine that being in the way, it should be exactly where the tail shaft rear
mount is for GM. I am not familar with how the T-45 differs from the TKO. I'd
assume it was pretty close. I didnt use the rear mount, I simply let the trans
"hang" off the rear of the engine like factory.

Here is a picture of the T-45 .. Doesnt look like it takes any more space than a
TH700-R4 .. which I installed in my old 60 Hawk, and used the crossmember I
describe above as my rear mount.



Tom

[BShaw]

[61Lark]

Bob, can you take a picture of the underneath of your car? To me the crossmember that you are talking about, often referred to as a batwing, should actually be underneth the bellhousing. This crossmember should be closer to the firewall and not the front seat.

Nick

[sbca96]

Nick, the one you are thinking of is the bellhousing crossmember, the one that
Bob is refering to has no driveline bolted to it, its structural, added in 1954 to
stiffen the wobbly frame the '53s had. The Lark uses the one you are refering
to mount the bellhousing AND the A-pillar, the Hawk body has the A-pillar further
back and uses a second crossmember. On the Avanti, the Lark style one is cut
off on the outside of the frame on each side of the car.

Tom

[PlainBrownR2]

The crossmember I think Bob is referring to, is the batwing that is behind the transmission. It is probably like the one I had to reinstall in the '55. It was completely gone when I got it out of the weeds. It is affixed to the lower part of the frame and the lower door posts and if I recall is used to keep the firewall stiff, as well as affixes the firewall underneath the frame. It's not attached to the transmission, that crossmember just goes underneath of it. If I also recall, since the floors were good, it kept the car's body from breaking in two, so the crossmember just provided additional reinforcement. If that is temporarily removed it should not do anything to the frame or chassis. However, if the crossmember in front of the wide flat crossmember is removed, the one that the transmission is attached to, that might cause some problems since that crossmember is what affixes the transmission to the frame, and also provides a place to stiffen the chassis, since that is installed inside the frame rails. In short, if that is temporarily taken out, there shouldn't be any problems, but I would put it back in before taking the car out, so the firewall portion on the car doesn't flex back and forth.

[junior]

Are you refering to what some people call the 'bat wing' crossmember...and by screwing up everything are you refering to door alignment, body flex, cracking of exterior paint, doors being able to open/close etc?? If you are, then you're asking the question I am also seeking an answer to, as I would like to remove this crossmember without disturbing anything else on my car so I can modify it so I can R&R the transmission in my car with out pulling the engine. BTW, nice transmission! Junior

[BShaw]

No, I won't be touching the mount that holds the back of the engine up. It's good to know that I can safely remove the other "batwing" though as I can then more easily fit the T45RS and figure out any mods I might need to make with the tranny in the car.

Junior, I didn't have any problem removing my 3-spd OD by sliding it all the way back through that rearmost "batwing". It's a tight fit through there but a little wriggling did the trick. For a while I thought I'd have to remove the OD solenoid but didn't need to.

[junior]

Junior, I didn't have any problem removing my 3-spd OD by sliding it all the way back through that rearmost "batwing". It's a tight fit through there but a little wriggling did the trick. For a while I thought I'd have to remove the OD solenoid but didn't need to.

My car isn't stock, right now the trans. is a turbo 350, and the rear mount is welded to the 'bat wing'. I'm in the process of converting to a 5spd. as well, and had the same question as you...can the 'bat wing' be removed and replaced without dire consequences. Thanks all the same. Good to know it can be done. Junior.

[PlainBrownR2]

I guess to put it one way was when I pulled the '55 from it's resting place, it required pulling it first with my pickup, and then using the tractor to pull it up by the house. It rolled great, but that meant having to pull it over some pretty rough ground. The batwing was all but disintegrated underneath from years of sitting outside, so the only thing really keeping the car together was the floor, door sills, and the firewall. The body was flopping quite a bit, but that was alleviated when I welded in some 1 inch square thicker metal at the lower front corners of the door sills that connected the floor to the doorpost, and the firewall. That's also how these cars get weak over time, when the lower door sill in that spot rusts out, the batwing, and in my case the torque boxes rust through, the only thing holding the back and front half of the body together is sheetmetal in the floor, and it's not very thick, so it will cause the body to flex quite a bit, lol.
Anyway, once I welded in the 1 inch square metal, even without the batwing or the torque boxes, I could hold a square dance on that floor now, as the little bit of metal reinforced the door sills, and the entire front structure of the car. The underside of that car was now very solid. I still had to build the torque boxes, and I had to buy another batwing. The batwing came from a used 56 Packard Hawk. Due to the age and the level of rust under the frame rails, the old batwing had to be cut out along with the lower part of the frame rail from the underside of the car. The lower half of the frame rail had flood rot in it, so I had to mend the frame rails with fishplate the frame back together anyway. Once the frame rails were repaired, I welded some studs under the frame rail, and welded some studs to the doorposts, and bolted the new batwing up in it's place, without any problems with the car splitting in half while there was no batwing underneath of it. Like I said, the batwing should be able to drop down without any immediate adverse effects, as it's there to tie the firewall and front half of the car to the underside of the frame .