I'd like to hear your thoughts and experiences on ratio spacing as I mentioned, and......

Your thoughts and experiences on 4L60 durability behind a 5.3 V12.

In my previous V12 days I nearly did the 4L60 swap but changed my mind. I asked several experienced GM trans guy and a couple guys specializing (or claiming to) in modifying 4L60/700R4 transmissions about potential problems in the 6000-6500 rpm range the that 5.3 is easily capable of and which I visited rather frequently.

To a man they all strongly cautioned against a stock-spec 4L60/700R4 for use under those conditions. They all suggested upgrades. Their opinion that, in stock form, these transmission are simply not built with enough precision nor are a couple key components (I forget now which ones) capable of reliably staying in one piece at that rpm level.

In the end I abandoned the idea because the conversion kit, trans itself, rebuild, and upgraded parts would've been too expensive for me at that time.

I might revisit the idea now that I have a V12 again.

Thoughts and experiences?

Cheers
DD

 

My 4L60 has been upgraded and all worn parts replaced. I was aware of the short comings of the 4L60 and mine is a 94 so one of the worst for longevity behind a powerful engine. This is why I spend over $1000 just in parts to upgrade it.

Heavy duty clutches and steels
Sonax reaction shell
New reverse input drum with wide band
Genuine Delco 5 pinon rear planet
Sonax 2-3 shift valve (allows engine braking in 1 and 2)
Corvette servo.

And of course all bushes etc were replaced. I had a shift kit installed and I would not do this again 1 2 shift is a little too severe.

It will chirp the tyres into 2nd gear and pulls well. I think the torque of the V12 is wide enough not be an issue with the wide 1st to 2nd ratios. Sonax have a close ratio gear set that raised 1st and lower 2nd gear.

We'll see how it holds up behind the 6.7L with at least 450ftlb torque.

I have heard that the 4L60 does not like to be reved hard and I have set upshifts at 6000rpm.

 

Doug,

I'm a dreamer not an owner. My circumstances prevent me from owning a car. I'm living in Venezuela and my company car is an armoured Ford Explorer driven by a company driver. I've owned some nice cars in Australia and Singapore but not in the last 8 years. But I'm in the US frequently and rent V8 Camaros and Mustangs to get my kicks. The eight speed auto in the Camaro is awesome, 0-60 in 3.9 seconds and shifts faster than a Porsche PDK.

It's going to be very interesting to see how the latest mustang GT performs as it's going from a 6 speed auto to a 10 speed.

GM and Ford 8 and 10 speeds were developed jointly so basically the same boxes.

The big gap between first and second is not an issue I'm guessing because once 1st delivers the torque needed to get a stationary car moving 2nd can be a lot higher. The spread of the ratios is the interesting thing, generally 4 on a 4 speed, 6 on a 6 speed and 7 on a 8 speed. The low 1st on the 6 and 8 speeds really adds punch but need traction control to control things.


4L60 ratios 3.059 1.625 1.000 0.696
6L80/90 ratios 4.027 2.364 1.532 1.152 0.852 0.667
8L80/90 ratios 4.56 2.97 2.08 1.69 1.27 1.00 0.85 0.65

Torque is also an issue for selecting the right transmission and new transmissions are more capable.

4L60 max tq 360ft/lbs
6L80 max tq 430ft/lbs
6L90 max tq 531ft/lbs
8L90 loads - that put it behind the 650ft/lb engines in a caddy and the corvette.

Warren also mentioned the size of the 6L80/90 would create issues. The 8L80/90 is the same size as the 6L80/90.

My interest in Jags stemming from a ride I was given in an XJS when I was 15. I never forgot it.

Cheers
John

 

Broadly I agree but still have reservations. OTOH I realize that my reservations might not actually materialize in real-world driving situations. Warrjon's remarks certainly suggest this.

The V8 Mustangs and Camaros have gobs of lower RPM power/torque. A 5.3 Jag V12....not so much. The 5.3s need to be worked up to a boil, if you get what I mean.

Of course, more aggressive diff gearing may eliminate this concern.

Cheers
DD

 

Wouldn't the steep first gear help put the V12 into its boiling zone quicker? If you take 1st gear to 6,000rpm then 2nd gear should start at 3,000rpm + and on the boil.

 

One thing I forgot to mention is the torque converter, I'm running the stock converter ATM and I think it has an issue with 6000rpm, a better converter is definitely needed.

 

when i made the change from 400 trans. to 700,trans, some things i was aware of,

#1 a rear final drive gear of 3.73-1 that alone almost doubled my rear TIRE torque!

#2 a change of converter size from 12" diameter, down to a 10" diameter, much lighter weight(quicker accell.), and not a problem with RPM issues.

i also use a GM truck 700 trans, 1990 much improved for torque capacity, last yr for cable TV ,before elec. was changed.

B&M shift kit made better shift points firmer. and can hold gears till HP dropoff point.

altho for interest , my 1st to 2nd comes at 6200rpm when full throttle, regardless.

at that point car may go side ways, or you grab another gear, (mark that as FUN).

but at low rpm shift is quite firm, with a chirp from tires!

it can be tuned out by cable adjustment but then other gears are soft,(its some thing i'm used to tho).

but all and all been 22 years and trans is still solid!

 

it would be great to drive a 12 cylinder with an 8L90 trans?

i just cant imagine the experience , but sure would like to try!

would keep right in the perfect peak torque RPM, when full throttle WOWEE.

 

Agreed.

This outfit made up a converter for my old XJS.

https://www.tciauto.com/

Not cheap, and not much help on your neck o' the woods. But they were very helpful and when I mentioned "Jag V12" the guy wasn't fazed a bit and had a good idea of what I would need and want.

Cheers
DD

 

Sure, in first gear you'd scream

3000 rpm is a bit shy of boiling on a 5.3 V12. More like 4000, really.

I'm just judging from my experience with the 400 trans. The ratios were 2.48, 1.48, and 1.00. I remember wishing for closer gear ratio spacing on the 1-2 shift. The 1-2 spread is even wider with the 4L60 so it seems, on paper at least, that I'd be wishing even harder.

Or not.

Judging from what other have said it doesn't sound like it's an actual problem. And my old V12 was hampered by the 2.88 diff....so that definitely enters into the equation.

In my dream world, if limited to 4 speeds, I like something along the lines of 3.00-2.20-1.40-.80

Cheers
DD

 

Sonax have a close ratio set for the 4L60 at 2.84, 1.55 which is closer than the TH400

 

The 6.0L V12 had the GM 4L80E transmission fitted by Jaguar
4 speed auto with lock up torque converter.

This article comparing 4L60E and 4L80E states the latter is much stronger and capable of higher torque and power outputs

4L80E Transmission Swap - GM High-Tech Performance Magazine

 

.

great article, no doubt the 4L80E is a very good trans.

its basicly a 400 with overdrive added(strong).

also there is a shift kit for them that converts the 4 speed to a 6 speed, by manipulation of the overdrive between gears!

but the #1st gear is same ratio, and final overdrive is the same stock ratio.

to each his own?

 

That's fairly common these days. However, it doesn't work for the version Jaguar used, it's a different case that GM used after Jaguar quit using the 4L80E, and not retrofittable.

 

I looked into the 4L80 6x but the PCS valvebpdy is not compatible with all versions o the 4L80e, IIRC it only fits 1996 and up transmissions.

The 4L80e is strong but I think with the modest power from a V12 the 4L60 will live. Ron had his 700R4 in for 20 years or so and this is the same internals as the early 4L60's

 

for a street car, the simple way is have a tire with some limited grip!

that way instead of breaking the transmission ,tires slip a just a bit, and reduces the shock in the drive line!!

just simple old American Hot Rod ideas!

 

I agree.

Plus, the 700/4L60 is quite bit less parasitic than the 400 and 4L80. I remember, a million years ago, some of the hot rodders were building TH350s to take some abuse so they could be used in place of a 400. it was like gaining 15 horsepower.

Cheers
DD