Manual Transmission Swap_Issues

[Sean C]

Hey all! Sorry I've been posting so much, but you guys are just too helpful!

So, I'm going with an EFI system for my truck. The motor only has around 3000 on her, same for the TH350. I want to do an LS swap, but for now the EFI and a manual will make me plenty happy.

The issues...
From what I've read, the T56 is the best option, but having a bench seat, I'm wondering how I can have the shifter placement adjusted? I heard of a kit for the adjustment, but couldn't find much more on what it is or where to buy, so any help there would be great.

Also, the previous owner of my truck had the original rear end rebuilt. I believe it's a 3.02? Some clarification on that would be great The reason I bring that up is because I'm concerned the T56 being double overdrive would not pair well with the 3.02. Is this an issue? New gears?

Thanks for all your help so far guys! I'm doing my best to gain as much knowledge from previous forums as I possibly can and very much appreciate your direct responses.


Sean

[Lugnutz65]

I think the kit to relocate the T56 shifter to the forward location is pretty pricey, but that's just going from memory.

Four things are involved when matching up a transmission to your driveline. They are:
tire diameter
rear end gearing
transmission gearing
engine RPMs

You really need to run some calculations before you spend money on an expensive transmission. Also, your engine will need to have enough HP to run the OD gears.

I'll talk about examples I am familiar with. The 1989 Camaro with a 2.8L V6 had a manual transmission with a 4.03 1st gear and a 0.76 5th gear, a 3.42 rear diff and a 26" tire. The 4.03 gave it enough power to get going in 1st gear. The 0.76 5th gear gave the engine 2351 RPMs at 70 MPH for nice cruising. The 2.8L engine needed those 2351 RPMs to maintain the proper horsepower.

If you run a 3.08 rear end, then you really don't want a 5th gear that is too tall or your engine will lug because of low RPMs.

Here's an example from my own build. I recently sold a really terrific transmission because I realized the 5th gear would likely lug my engine. It was a T5 from a V8 Camaro and it had a 0.63 5th gear. Calculations showed that my engine would only be doing 1974 RPMs at 70 MPH with a 28" tire and a 3.73 rear. That seemed OK. However, the engine would likely lug with only 1692 RPMs at 60 MPH and I'd end up downshifting a lot. If I had more horsepower, it would have been just fine. So basically, the 5th gear was only useful for 70 MPH and up. I don't plan to drive my truck much over 70 MPH so I sold that tranny and got one with a 0.73 5th gear. A much better match for my 28" tire, 3.73 rear and L6 engine.

Choosing a smaller tire would fix my problem but would look funny on my truck. For me, getting a lower rear end would have been a lot more work than finding a different transmission. Same would be true for getting a stronger engine.

I can't stress enough how important it is to run some calculations incorporating all 4 factors.

[Captainfab]

If your truck does has a 3.07 rear gear, I would not recommend going with an OD trans. As mentioned above, too low of rpm's is not a good thing. The engine needs to run in a rpm range where it is efficient. IMO a good rear gear for an OD trans is 3.42 to 4.11, depending on the size of tire being run, the OD ratio and the intended usage of the truck.

[Sean C]

Originally Posted by Lugnutz65

I think the kit to relocate the T56 shifter to the forward location is pretty pricey, but that's just going from memory.

Any idea where to find it?

Awesome info! I thought the RPMs would be too low, but was just making an educated guess. What would the calculations be? Are there formulas somewhere? I think switching to a taller rear end gear would be a good option here, especially since I wanted to put in a taller one anyway. I'll have to figure out my tire size and I'll look around for more info on those calculations.

Sean

[Rich 5150 69]

Here you go....
http://www.gtsparkplugs.com/GearCalc.html

[Sean C]

Originally Posted by Rich 5150 69

Here you go....
http://www.gtsparkplugs.com/GearCalc.html

Thanks!

[Lugnutz65]

I must not look at the T-56 too long, . . . . . . because I want one. Not really useful to my application . . . . . . but I want one anyway!

This link shows what the midshift relocation kit can do to move the shifter forward. LINK

For RPMs - I use the calculator all the way down at the bottom of the page of THIS RPM CALCULATOR LINK.

I like THIS LINK too. Pretty easy to use. You can play around and figure out at what speed you'll need to shift for each gear.

[kieth]

Originally Posted by Sean C

Hey all! Sorry I've been posting so much, but you guys are just too helpful!

So, I'm going with an EFI system for my truck. The motor only has around 3000 on her, same for the TH350. I want to do an LS swap, but for now the EFI and a manual will make me plenty happy.

The issues...
From what I've read, the T56 is the best option, but having a bench seat, I'm wondering how I can have the shifter placement adjusted? I heard of a kit for the adjustment, but couldn't find much more on what it is or where to buy, so any help there would be great.

Also, the previous owner of my truck had the original rear end rebuilt. I believe it's a 3.02? Some clarification on that would be great The reason I bring that up is because I'm concerned the T56 being double overdrive would not pair well with the 3.02. Is this an issue? New gears?

Thanks for all your help so far guys! I'm doing my best to gain as much knowledge from previous forums as I possibly can and very much appreciate your direct responses.


Sean

before you dive off into this conversion lets see how your truck is going to perform with the changes you are talking about.

I need the following information, just send be a private message here with the info and your email address (I cannot send a excel spreadsheet to the board.)

1. engine

2. tire diameter from ground to top of the rear tire

3. rear axle ratio

4. transmission with final od ratio, t5s have around 4 ratios

then I will send you back a spreadsheet that shows:

1. torque within a usable range of speeds for all available rear axle ratios and common engines.

2. speed at 1500, 2000, 3000, rpms for all rear axle ratios



this way you will not end up with a engine, trans, tire diameter , rear axle ratio that will fall on its face........Kieth

[Lugnutz65]

Originally Posted by kieth

before you dive off into this conversion lets see how your truck is going to perform with the changes you are talking about.

I need the following information, just send be a private message here with the info and your email address (I cannot send a excel spreadsheet to the board.)

1. engine

2. tire diameter from ground to top of the rear tire

3. rear axle ratio

4. transmission with final od ratio, t5s have around 4 ratios

then I will send you back a spreadsheet that shows:

1. torque within a usable range of speeds for all available rear axle ratios and common engines.

2. speed at 1500, 2000, 3000, rpms for all rear axle ratios



this way you will not end up with a engine, trans, tire diameter , rear axle ratio that will fall on its face........Kieth

Listen to Kieth ^^^^^^^^

He knows what he's talking about. His info and spreadsheet will be very helpful and get you headed in the right direction.