About to order a Kirkham; seeking transmission advice

[Mark Thompson]

I am about to order a Kirkham 427 SC chassis and was looking for some advice. I am planning a 468 aluminum block of around 500 Hp +/-, probably sourced by FE specialties ( I live in the SF bay area). The big as yet unspecified item is transmission. It looks like there a several choices in 4 and 5 speed. What are peoples favorites in terms of durability and shift linkage? Also, what vendors have people had good experience with? What ratios do people recommend? The car will have the standard Kirkham sourced differential (don't know ratio yet). The car will get general road use, occasional autocrossing, and rarely taken on the track.

Many thanks for any help folks can offer.

Mark

[bnewell]

Welcome Mark......Kirkhams are great cars....I sure miss mine. Not sure what my rear end ratio was (bought it used), but I wish it would have been a 5-speed.

Good luck,

B.

[Tom Kirkham]

Mark glad to hear the news. We have had several customers convert from four speeds to five speeds. We have had a few customers change from the .64 to the .82 fifth gear, but we have never had anyone change out a .82 gear box. Most common comment after the conversion was: "why did I wait so long?"

[twobjshelbys]

4.54 rear end with a Tremec TKO600 with .82 5th.

[patrickt]

Originally Posted by twobjshelbys

4.54 rear end with a Tremec TKO600 with .82 5th.

That's a typo, right?

[lemans24]

tko 600. the electronic speedo plugs right up to Kirkham Gauges I got mine from Standard Transmissions w/ short shaft already installed. 5th gear is nice on the
freeway.

[*13*]

For nostalgia sake, I like the four speed. I do, however, find myself reaching for 5 quite often. What's important to you?

[twobjshelbys]

Originally Posted by patrickt

That's a typo, right?

if you say so

[patrickt]

Originally Posted by twobjshelbys

if you say so

You really have a 4.54 rear end?

[twobjshelbys]

Originally Posted by patrickt

You really have a 4.54 rear end?

Yep, 3.54.

I do know some people with 4.10s, not exactly street or highway cars.

[patrickt]

Originally Posted by twobjshelbys

Yep, 3.54.

I do know some people with 4.10s, not exactly street or highway cars.

Well, you had me going alright.

[ratsnst1]

get the 5 speed, you will love it on the freeway, you wont be all tached out.

[twobjshelbys]

Originally Posted by patrickt

Well, you had me going alright.

Just so you know, this config is very torquey. I strongly discourage using the transmission downshifting to slow down. [They used to teach you that in drivers ed.] If you do it, for example, from 3rd to 2nd turning into an intersection, you might find a curios 540* effect in the middle. I've posted a "Transmission Go, Brakes Slow" sticky note on the windshield as a reminder.

[Anthony]

The tremec TKO600 has the same gear ratio's as a wide ratio toploader, but an added overdrive.

With the 2.78 first, you can run a 3.07 rear (what I would recommend with a WR toploader), and have a respectable start-out, and have some cruising benefits.

With the TKO600, you can run the 3.54 rear, and still have a respectable cruising with the OD gear, or you can choose to run a 3.31 to 3.07 rear as well.

With a CR toploder, you pretty much run a 3.54 rear, maybe a 3.77. The gear spread is closer spaced, what I like better, and I don;t use it as a daily driver, so cruising in 4th is tolerable, as all of the muscle cars were back in the sixties. Most ran 3.55, 3.54, 3.73, or something like that, without OD, and using 14" tires. You don't necessarily need an OD, but it's nice. I'll keep my CR toploader.

[Jamo]

WR Toploader with a 3.31. Great for autocrossing (fewer shifts) and open track and not bad at cruising speeds.

Whatever you want...David Kee. The Kirkham(s) of transmissions (or are the Kirkhams the Kees of Cobras?)

[RodKnock]

The standard Kirkham rear end is 3.42. Get the 5-speed TKO600 with the 0.82 5th gear, best of the available choices. Buy from Fortes, or Brent from B2, both Club Cobra sponsors and nice guys.

[pusherfans]

The new standard Kirkham differential ratio is now 3.54. Before that it was the 3.42. There is not a lot of difference between the two.

I like the Tremec TKO 600 (purchased from Joe from Standard Transmission - http://www.standardtransmission.com ) They have been great.

I have the .82 OD, but if I had to do it again, I may change to the .64 OD. I am rarely on the highway and so I rarely use 5th gear as it is (engine likes 2000 RPM and higher due to big cam).

But when I am on the highway, it would be nice to drop the RPM's a little more than the .82 provides. But I think it's a risk, a .55 or so would be perfect in my opinion, but it is not an option.

That being said, I am not spending the money to convert to .64 OD (I was quoted ~$600) since I have doubts that it would be too low a ratio.

Hope that helps.

ps. I made a chart with the different ratios. I could not attach it for some reason, but email me if you want to see it.

[RodKnock]

Originally Posted by pusherfans

The new standard Kirkham differential ratio is now 3.54. Before that it was the 3.42. There is not a lot of difference between the two.

First, bummer. 20/20 hindsight, and I know there's little difference between the 3.42's and the 3.54's, I would prefer the 3.54's. My car feels like it wants more gear, probably because of the cam. At around 70-75 MPH, my car wants just a tad more gear. 2,000-2,200 RPM is works great, but I wouldn't mind being a couple hundred RPM higher.

I like my 3.42's with the 0.82 5th gear. I would NOT like the drop in RPM's, if I had gone to the 0.64.

[FatBoy]

I have a CR Toploader with a 2.88 rear end and I'm happy with it.

80mph is around 3,000 rpm.

Paul

[dcdoug]

I have a TKO 600 with a .82 OD and a 3.31 rear end and am very happy with it.