Thinking about a auto to manual swap in my 90 5.7 IROC.
Prefer not to do any cutting to install
Have 3:73 gears.

Looking at the kits from Hawks

 

I had the same question as I dont know how much cutting of the car needs to happen to get the T56 in there. Id also prefer not to cut the floor. Just dont know anyone who has used the TKX though either

 

There is NO way to swap an auto to a manual transmission and not cut the trans tunnel for the the shifter. You got my scratching my head here. There's NO hole at all!

Accept it, you are going to have to cut a hole in the tunnel for the shifter, and you are going to have to drill holes for the clutch.

 

Never did understand the 'I'll spend $5k on xyz speed parts but not $500 on power tools' approach.

 

I should have been more clear in my first post.
I assumed that the modifications for the shifter and clutch would be understood and be done for both.

My question was directed towards the T56 needing more clearance and having to "cut" the tunnel to fit and WHY one would be a better choice over the other.

 

I think it's safe for me to say I have more than "$500 on power tool's"

 

You don't need to cut anything in the tunnel other than a shifter hole for the T56 or derivatives of it (Magnum etc). I believe even the auto cars have an outline in the Sheetmetal where the shifter hole surround plate was welded. I don't have any experience with the TKX, but its hard to go wrong with a T56.

 

Thanks ShiftyCapone

This is the first I've heard of a shifter hole surround plate.
Do you have any Pictures?

 

Yeah, the factory welded a perimeter shallow channel around the hole. Your best bet is to find a junked 5sp car and cut it out of the floor. You could then stitch it into yours.

 

There is no cutting needed other than the shifter hole on the trans tunnel for the t56.

I drilled out the auto shifter bracket spot welds when I did my t56 conversion and I ended up with a VERY small hole, far smaller than the stock t5 hole.

basically perfectly sized.


T56 shifter hole cut.

T56 shifter hole cut.

 

I've started searching for a shifter hole surround plate.

 

I've never seen a "shifter surround plate", as such.

If you look closely at how the car was built, you'll observe that the transmission tunnel is a separate piece from the firewall, floor pans, etc. Whether a stick or auto one, it welds into the same place, but has different features. The auto one has the bracket assy stuff for the auto shifter attached to it, and has a nice ... hole ... (for lack of a better word...) for the shifter cable. The T-5 tunnel has none of that, but instead has a sort of rectangular reinforcing ring welded to the underside, that gives a more secure mount for the "lower boot". More layers of sheet metal for the screws to grab onto.

Having seen any number of these cars in junkyards back when they were plentiful there, and observed carefully, it's obvious you can drill out a few spot welds, and change out THAT WHOLE PIECE and spot-weld it in while filling the holes left from drilling out the original ones, and it would be as if the factory had done it.

There's about 8 or 10 spot welds holding in the "ring" thing around the shifter, that reinforce where the "lower boot" bolts to it. Not "hard" to take one off, but not exactly "eeeeezzzy" either. I'm not positive whether all of the auto trans features (like the shifter cable hole for example) go away if you cut it out to the T-56 hole size, butt it's entirely possible. I'll defer to others who have done a auto –> T-56 swap in this matter. The above pic is somewhat convincing: looks like it left only a few spot weld holes to be filled or covered over. Fairly sanitary if that's the case.

For a T-5 –> T-56 swap, you have to enlarge the shifter hole about ľ" toward the rear; which leaves a certain amount of the reinforcing ring.

You don't really "have to" have the reinforcement for the "lower boot", but it, or something like it, would sure be A Good Idea. The stock boot at least, is pretty stiff, and would eventually crack and break out just the tunnel sheet metal, without anything backing it up. Maybe if you used something a bit cheeeeezzzzyer, like maybe a Mr Gasket boot or some such, there'd be less stress, and the tunnel tinfoil would last a bit longer. Can't say; never done it myself. Only a T-5 –> T-56 swap with minimal invasion.

 

I found someone with a T5 parts car that I could pursue for the floor section and pedal assembly.

Does the T5 shifter hole need to be enlarged to fit the TKX?

 

Pic of my 88 GTA that's factory 5 speed.

 

BigBlock73, I would check the cruise RPM with whatever axle ratio you have with the final drive ratio in the transmission. My GTA has the .73 5th gear with 3.45 ring and pinion and 245/50 tires. On a 4 lane/Interstate it's terrible. Way too many rpms at 80 mph. Just something to think about.

Edit: I'd go T56

 

Brian

Thanks for the picture, it's a great reference.

My car has 3.73 gears and 245/50/16 tires.
The 700r4 that's in it now (as per the internet) 1: 3.059 2: 1.625 3: 1.00 4: 0.696 R: 2.294


The TKX has .72, .81 and .68 options for the final drive

 

FWIW, I went with the .68 fifth gear, so I'm at about the same RPM as I was with the auto transmission. With a 3.73 and .68 fifth gear, you'd be looking at about 2,500 rpm at 75 mph.

 

Or consider the magnum f 6spd. It’s basically a tr6060 in disguise. Significantly stronger, and you can go with a close ratio or wide ratio model.


I’ll always opt for the close ratio,but that’s me and my love for high revving v8.


im thinking of upgrading from my t56 to a magnum f. My ratios are too wide, and it hates me when I shift up a 7000rpm. I can shift hard all day long at 6500, but at 7000 I need to be slow the shifting action down or the synchros will lock me out sometimes.

 

Yup I swapped it over from my manual body to my auto body on my last build. Also added a factory style clutch master support plate

 

midas
Did you cut the hole and then add the surround ring?
Did you make the clutch master support plate?

sofaking

Having seen any number of these cars in junkyards back when they were plentiful there, and observed carefully, it's obvious you can drill out a few spot welds, and change out THAT WHOLE PIECE and spot-weld it in while filling the holes left from drilling out the original ones, and it would be as if the factory had done it.

How much of the tunnel is this section ?

Thanks for everyone's time

 

I had a t5 donor car so I cut the hole from the trans tunnel out of it then used it as a template to cut the new hole. I also ground out the spot welds on the support ring and welded it in factory style to the new body. I made the clutch support from sheet metal it seemed too annoying to cut out of the other car at the time.

 

FWIW you do not need a hole that is nearly as large as what they did in the factory. When I did my swap I cut the hole maybe 3/8" wider in all directions than the base of the shifter plate.

I'd recommend going TKX if you have the money. Smaller, less modifications, plus 1 overdrive gear is plenty haha.

 

So if thats the case I have a manual car now and swapping an LS and Tremec into it. If its currently a manual trans now would a Tremec also go in with no clearance issues and of course needing the proper cross member but should bolt in with no other major modifications to the floor of the car?

 

What modifications over a T56?

If you are starting with an Auto car the mods are basically the same. Some of the parts used change, but the modifications needed for the chassis remain.

Cut the holes for the 3rd pedal and shifter.
Rewire the neutral safety switch from Auto to a manual switch, etc.

The extra gear is worth it so much for highway cruising.

 

I thought that the t56 required tunnel modification to allow it to fit because of the larger case 🤷‍♂️

 

The only T56 fitment issues would be if you have a trans out of a 5th gen camaro or CTSV. In that case, you'd have to swap the tailhousing due to the awkward shifter extension. Otherwise, there is zero fitment issues with the T56 or Tremec Magnum units. If you want a larger selection of crossmembers buy a unit that has an F-body tailhousing so that the torque arm can mount to it. Or, buy a torque arm relocation crossmember such as the Holley Blackheart unit if you opt for a regular magnum. Note: If you go with a Magnum and use the universal tailhousing it comes with, your shifter will be 2.5" forward of stock and will interfere with the console plates/ashtray. They now sell them with the F-Body tailhousing though if you are buying new.

I did have to modify my tunnel slightly because I have the standard magnum with the non F-body housing.

 

Nope, T56 fits just fine no other special modifications.

Which is why, if I was going aftermarket, I'd go Magnum-F Close Ratio.

 

The only problem with the close ratio is the final overdrive is .50 which if you have non steep gears will bog the motor down at highway speeds. I have the stock 3.42 rear with the non close ratio magnum and at 70mph I am running 2k rpm. With the close ratio, I'd be bogging at 1600rpm. Just something to consider. This is how I run with a 305/30/R19 tire and 3.42 gear with the 11009 magnum.

 

If you want to play around with gearing, you can make a copy of this Google sheet. I've preset it to a 94-02 F-Body with 3.42's and 245/40/17 tires ( like the SS and TA came ).
https://docs.google.com/spreadsheets...gid=1747947528

Just make a copy of it, and then you can edit it.

I already have nearly all the T-56, TKX, and thirdgen T-5 combos I know of in there. You can just use the drop downs to select which transmission, and Axle ratio you want, and adjust the tire size to match yours.

 

You can get a close ratio that has a .63 final.
TUET16362 2.66 1.78 1.30 1.00 0.80 0.63

The Google sheet I made lets you switch transmissions, axle ratios, and tire sizes around easily, and then maps out what RPM you'll be doing in each gear up to 8000rpm. It also shows you driveshaft speed for 5th and 6th gears, so you can get an idea if you should bother attempting that at all.

 

Well I'll be......Must be a new offering. I see it as an XL on their site, sans the part number. Good tip! Wish this was available when I bought mine.
Edit: The XL version is not out yet, this is the F-Body version. This indeed is the unit to get IMHO.

 

Personally, I would prefer the RSGear set, SUPER close ratios. But that is my personal preference and probably wouldn't keep many other people happy. But then again, I take my GTA to 7200rp, and it does NOT make good power below 3500rpm at all. And I'd prefer to build an even higher revving engine that peaks in the 8000rpm range. Heck, I can't EVER let my engine fall under 1700rpm on the highway in 6th, or it literally doesn't make enough torque to pull itself out of that hole.. And it shakes/shimmies pretty hard under 2200rpm in 6th too.

 

Not great pics, but more of the extra sheet metal surround. For reference.

 

Saxondale
Thanks for the pictures

Thirdgen89GTA
My car has 3.73 gears and 245/50/16 tires.
The 700r4 that's in it now (as per the internet) 1: 3.059 2: 1.625 3: 1.00 4: 0.696 R: 2.294
Going to put a TKX in.
Will be only used as a cruiser and wondering which TKX to get

 

Look at the google sheet I posted. You can swap the transmission with a single click and see how RPM drops between gears and match that against your powerband.

 

Excuse my computer skills

I can change the trans and gear ratio but the box on the side still has your tire, rim size

 

Can't go wrong with a T56 as long as it doesn't need any work. Used values are pretty high though, so if it needs work it really begs the question should you just buy something else new instead.

Personally I'd get a 6-speed over a 5-speed. Both can have similar power gears (1-4), but the double overdrive makes highway / freeway cruising nicer.

These examples people are giving of how their engine is lugging in overdrive is not because of their transmission, it's because they don't have enough rear gear. They're probably dogs in 1st gear too and desperately need a gear change.

 

You should be able to edit it to match your tire sizes, its not a drop down, so you have to manually enter the numbers in Column N3, through N5.

It doesn't change much though, the tire height difference only goes from 25.66" to 25.65" between 275/40/17 and 245/50/16.

I added a RPM @ 70 in 5th to cell N9, since some people may want to know RPM at 5th.

 

And typically when going from auto to manual trans you will need more rear gear (numerically higher) because the clutch locks up and you lose the advantages of converter slip in 1st gear. Basically you need the extra gear to get the car moving easier in 1st.

 

I know and understand that 4.10's would make my car happier, however, I have specifically not changed my 3.23's out for 4.10's because it allows me to keep my max speed at RA in 4th gear, rather than upshifting to 5th gear. This is because it keeps my drive shaft speed at 160mph around 6800rpm, instead of nearly 9000rpm. And because should I ever decided to stretch its legs to its real limit, I'm not running nearly 11000rpm on the driveshaft.

The OP's engine will never reach these engine RPM or MPH speeds. Its as specific thing to the way I built my car and what it was built to do, which is towards larger high speed tracks like RA or just plain top speed runs. So I sacrificed off the line performance. I primarily use 5th gear for highway cruising unless we are going over 65mph, then I switch to 6th gear.

A stock cammed 305/350 will likely be perfectly happy cruising the highway at 1300rpm with no lugging.

 

I have 3.27’s and my 350 is happy, plenty of power in 1-4 and then a nice shift to 5th to cruise along.

 

Older cars are outfitted with weenie gears compared to modern cars. Look at drive ratio of a modern car and it is shocking how much gearing is there compared to older cars like ours. That is part of why the new cars are so quick and drivable.

That lesson learned can be taken into our cars when you swap in a 6-speed manual with double overdrive. Don't fear the gear! 4.10 axle ratio feels completely natural with a T56. Performance crowd has known this for decades, 4.10 or 4.30 standard in street cars. Better drivability in slow moving traffic, better wheel speed modulation to control wheel spin, and quicker 0-60 mph times, and deep enough overdrive to cruise.

If you're going to get the modern transmission then get the modern mindset too!

 

I'm only 1.5 Hours south of you, if you need any Wiring/ Electrical Work!

 

RPM @ 70 in 5th to cell N9 ?

 

vorteciroc

Stop by if you're ever in the neighborhood !

 

I have 3.73 gears and not interested in changing them.

Thanks for all the info and advice

 

5.7
11:1 compression
ZZ3 heads ported, stock valves
Accel Cam, Intake, Runners, Headers
SLP dual cat. back exhaust

 

I added it to the original sheet, so you’d have to make another copy.

 

 

Nice sheet. FWIW you omitted first gear for all the TKX boxes.