Bolt-in installation of T5 5-speed in a C1-C2-C3 for $1500

[Joe R.]

Attached is a pair of articles that I wrote for the New England NCRS Chapter newsletter (Part 1 in 2021 and Part 2 in 2023). These document my "research project" to develop a bolt-in solution for installing a T5 5-speed in a C2 with no cutting of the transmission tunnel. I believe the same solution will work for a C1 or a C3, provided that the C2 rear mount is replaced with a version that mates with the C1 or C3 frame mounting points.

The Part 1 article describes the key problem that has to be solved (shifter position), and a clever adaptation of a Camaro T5 that was described by Tom Austin on Corvette Forum. Tom's solution requires only a small amount of cutting the shifter opening in the fiberglass tunnel. The stock C2 console cover and boot conceal the cut.

I was surprised at how close Tom's installation came to requiring no cutting at all. Being an NCRS guy, I became interested in trying to come up with a no-cutting solution that might be attractive to other NCRS members.

At present, the only no-cutting 5-speed solution is a modified TKX. This is a very nice solution but it costs about $4000.

Since the T5 is a more budget-friendly 5-speed, I decided to take on the challenge of developing a no-cutting, bolt-in T5 solution for budget conscious owners who do not want to make any permanent changes to their C2.

The Part 2 article describes the no-cutting solution I developed, with a particular focus on low cost. My reasoning was that if you don't mind the cost of a modified TKX, there is no down side to just buying a modified TKX from Silver Sport Transmissions. The only reason to consider a T5 is that it is less expensive.

I used my '67 as a test mule for working out design alternatives and test fitting the prototype parts. Solidworks CAD files for all of the custom parts are available at no charge.

My hope is that the lower cost of the T5 option will persuade more C2 owners to enjoy the dual benefits of a 5-speed. Compared to a Muncie 4-speed, you get a lower first gear for better launch, and an overdrive top gear highway cruising.

If there are any C1 or C3 owners who want to make this conversion, I'd be happy to cooperate on developing suitable bolt-in rear mounts for the C1 and C3.

[Terry D.]

Re: Bolt-in installation of T5 5-speed in a C1-C2-C3 for $1500

So how much does a more budjet friendly 5-speed cost?

[Gary B.]

[Joe R.]

Re: Bolt-in installation of T5 5-speed in a C1-C2-C3 for $1500

Yes, as described the Part 2 article, I think that $1500 total can be achieved if you use a $300 Mustang T5 from a junkyard (remember, the focus for the project was low cost).

If you want a rebuilt T5, that adds another $200 to $1000 to the $1500 estimate, depending on how extensive the rebuild is and whether you rebuild it yourself or have it rebuilt professionally.

If the expenses for a rebuilt T5 get past $1500, I would suggest considering a brand new M-7003-Z T5 made by Ford Performance Parts and available at Summit Racing for about $1950. The M-7003-Z is the strongest production T5 ever made (about 10% stronger than the Mustang version that I used). And, it has a first gear ratio of 2.95, which some people prefer over the 3.35 first gear in the version that I used.

Another way to look at this is to separate the cost of the T5 from all of the other necessary conversion parts. In the minimum-cost conversion that I described, the properly-configured T5 cost $550 ($300 for the transmission, $100 to change the input shaft, and $150 to change the tailhousing). I think this is about the lowest cost that can be achieved to get the desired T5 configuration shown in Figure 2 of the Part 2 article.

So, for a properly-configured T5, the low end is the $550 that I spent, and the high end is the brand new 7003-M-Z for $1950 at Summit Racing. In between those two limits would be a range of other used or rebuilt T5 transmissions.

[Patrick H.]

Re: Bolt-in installation of T5 5-speed in a C1-C2-C3 for $1500

Excellent articles. I just read them both.
I look forward to Part 3.

I understand the desire not to get into selling kits to do this, but if "someone" did, I think they would be popular.

[Mark E.]

Re: Bolt-in installation of T5 5-speed in a C1-C2-C3 for $1500

When I looked into this a few years ago for my 1970, I identified these problems that companies with conversion kits didn't address:

- Insufficient tunnel clearance because of the battery cable
- No provision for the reverse gear/steering column interlock
- No provision for TCS.

As anyone made this work for C3?

[Joe R.]

Re: Bolt-in installation of T5 5-speed in a C1-C2-C3 for $1500

Hi Mark:

I'm interested in learnng more about possible C3 issues. In general, my impression is that there is slightly MORE room for a T5 in a C3 than in a C2. Having worked out a C2 solution, I had expected that a C3 solution would be easier.

Regarding the C3 battery cable clearance, is the cable in the transmmission tunnel? The T5 has very good tunnel clearance everywhere except right above the shifter. That area is the limiting factor for T5 tunnel clearance.

I'm not sure what the C3 "reverse gear/steering column interlock" is, but if it is electronic, there may be some versions of the T5 that support it. To my knowledge, all T5 transmissions have a switch that closes when the transmission is in reverse. And, all but the latest versions also have a switch to indicate that the transmission is in neutral. If you can clarify what is required, I will look into it.

Regarding "TCS," I don't know what that is. Can you clarify what that is?

[Mark E.]

Re: Bolt-in installation of T5 5-speed in a C1-C2-C3 for $1500

The positive battery cable runs along the tunnel from the battery box to the starter. It starts at the 2 o'clock position on the tunnel (looking from the front) and snakes to the 11 o'clock position as it travels forward. It's been years, but I remember a Tremec kit vendor saying to me that clearance is very tight in a few spots with C3 and when I asked about the cable, he didn't know if it would fit without mods.

The reverse interlock cable is connected to the Muncie's reverse shift lever on one end and a lever on the steering column near the firewall on the other end. This connection limits removal of the ignition key when in reverse gear, and locks the transmission in that gear using the column lock. With its internal shift linkage, it may be a challenge to connect the Tremec to this... but maybe someone has already done this?

Screenshot 2023-07-21 122825.jpg


Transmission Controlled Spark is an emissions control device that blocks vacuum advance in gears 1-3, and provides full vacuum in 4th. It includes a wire that attaches to a screw-in terminal on the side of the Muncie. This terminal is grounded when in 4th which trips a relay that allows vacuum to the VAC. This is for 1970; some of the other years have this or a similar system, but the technology changed over time. Many including myself bypass TCS so not accommodating this system may not be a deal breaker.

[Joe R.]

Re: Bolt-in installation of T5 5-speed in a C1-C2-C3 for $1500

The positive battery cable runs along the tunnel from the battery box to the starter. It starts at the 2 o'clock position on the tunnel (looking from the front) and snakes to the 11 o'clock position as it travels forward. It's been years, but I remember a Tremec kit vendor saying to me that clearance is very tight in a few spots with C3 and when I asked about the cable, he didn't know if it would fit without mods.

The reverse interlock cable is connected to the Muncie's reverse shift lever on one end and a lever on the steering column near the firewall on the other end. This connection limits removal of the ignition key when in reverse gear, and locks the transmission in that gear using the column lock. With its internal shift linkage, it may be a challenge to connect the Tremec to this... but maybe someone has already done this?

Transmission Controlled Spark is an emissions control device that blocks vacuum advance in gears 1-3, and provides full vacuum in 4th. It includes a wire that attaches to a screw-in terminal on the side of the Muncie. This terminal is grounded when in 4th which trips a relay that allows vacuum to the VAC. This is for 1970; some of the other years have this or a similar system, but the technology changed over time. Many including myself bypass TCS so not accommodating this system may not be a deal breaker.

Hi Mark:

Thanks for the detailed explanation of these 1970 C3 characteristics. I think that two of the three issues you describe can be successfully addressed. Following are some initial thoughts:


MECHANICAL REVERSE INTERLOCK

The mechanical linkage for the reverse interlock cable would be pretty challenging to support. There is no external shift linkage on the T5 (or the TKX) 5-speeds. It might be possible to add a mechanical sensor to the shifter that activates the interlock cable when the shift lever is in the reverse position, but there is very little room to work with between the shifter and the tunnel.

Inside the T5, there are a few points where the internal linkage moves into a unique position when the transmission is in reverse. It might be possible to drill and thread a hole in a strategic position in the transmission case to mechanically sense the reverse position and activate the reverse interlock cable.

It might be easier to simply not use the reverse interlock feature.



BATTERY CABLE ROUTING

If you talked to a Tremec kit vendor a few years ago about possible problems with battery cable fitment, the transmission that was being used at that time was the TKO 5-speed. That transmission is definitely a tight fit in the tunnel.

The T5 fits easily in the tunnel everywhere except the immediate area around the shift lever. And by the way, the new Tremec TKX five speed that is now being used by Tremec 5-speed kit vendors also has a lot more tunnel clearance than the older TKO that was being used up until the TKX came out.



TRANSMISSION CONTROLLED SPARK

Denying vacuum advance to the engine in gears 1-3 was an emissions hack that GM used to help pass the emissions tests. It compromised engine performance in exchange for slightly better results in emissions testing. I think you did the right thing to disable it. I can't think of any reason to retain that function.



Joe Randolph

[Joe R.]

Re: Bolt-in installation of T5 5-speed in a C1-C2-C3 for $1500

Excellent articles. I just read them both.
I look forward to Part 3.

I understand the desire not to get into selling kits to do this, but if "someone" did, I think they would be popular.

Patrick pinged me the other day to ask if "Part 3" of my T5 swap series was near completion. This reminded me that I should update this thread.

While I don't recall mentioning a future Part 3, I did say that I was working on a detailed set of installation instructions, with lots of photos. These instructions describe the "clamshell method" for installing the T5 without removing the engine. Even though it involves a number of non-obvious steps, I think the clamshell method is far less work than removing the engine just to install a transmission.

My draft divides the clamshell method installation into 23 small steps (the last step is to fill the transmission to the proper level of ATF), but I only have text and photos for the first 18 steps. I will try to get this finished and post it. Anyone who wants the see the current draft as it stands can send me a PM with their email address.

The good news is that in addition to the T5 swap I did in my own C2, four more of these T5 conversions have now been completed by others with good results. These conversions were done using my draft instructions and some phone/email support from me. All of these conversions used the above-mentioned "clamshell method" to install the T5 without removing the engine.

Three of these conversions used the stock GM bellhousing and my adapter plate to install a Mustang T5. The other two used the Camaro tilted bellhousing to install a Camaro T5 that was modified to use the Mustang tailhousing. All five installations were performed using the clamshell method that keeps the engine in the car.

Overall, I think it's simpler to keep the stock C2 bellhousing and use an adapter plate with a Mustang T5, but I can now provide technical support for installations that use the Camaro tilted bellhousing.

On Corvette Forum, there is a very long thread about the T5 conversion that I started back in 2019. Anyone who has read my Part 1 and Part 2 articles can skip the older posts and start reading at post #93 to get an update on what has been happening in 2024. Corvette Forum members MR14 and L78 both installed T5s in their C2s, and they posted a lot of photos. Here is a link to the thread:

Article on installing a T5 5-speed in a C2 - Page 2 - CorvetteForum - Chevrolet Corvette Forum Discussion

Going forward, I think my C2 conversion is pretty well developed now and proven in. I remain interested in working with someone who wants to try the T5 conversion in a C1 or a C3. I think the only thing that needs to change is the rear mount.