: toeing? um, towing!



Richard Miller
06-14-06, 09:06 PM
I really cant find any info on this. I would like to be able to tow with my 1979 deville. the trailer will most likely weigh in around 5000 lbs. give or take. I have a manual rear shocks, but would like to add the auto level. can anyone give me any advice on this. It seems that the tranny is up to the challenge. The wheelbase should be fine. la te da... I do not want to get a truck, or a suv when I already have a frame on v8 with rwd!

thanks

Night Wolf
06-15-06, 02:05 AM
Heh... whatta know.

First up, the 425 is up to the task, the TH400 is up to the task, as well as the 8.5" 10-bolt rear end. With a chassis good to the tune of 7,000lbs, you are set. Does your car have the factory towing package? The only real thing that helps it in towing would be better gears... if you don't have it, then you have 2.28 gears.

Now she'll tow fine witht he 2.28 gears, the 425 really dosn't care... but it just wont be fast....

My father had a '79 Coupe DeVille and towed his 18' Sea Ray. The boat, trailer and supplies were around 5,000lbs.

The car towed the boat fine, my father said it was like it wasn't even pulling anything. What that setup was really bad for, was pulling the boat out of the water... it was quite the smoke show. That car is since long gone, his last tow vehicle was a '85 Bronco 351 HO 4bbl factory towing package (beefy truck.... C6, 4.11's, 9" rear etc...) The Caddy did a better job at towing... both with more power and the longer wheelbase.... where the Bronco with the 4x4 shines is pulling the boat out of the water.... no more smoke shows and spending an hour trying to do it.

That Coupe was mostly stock, the tranny was rebuilt with a shift kit, the cat was removed, and my father tweaked with it a bit for more power.... I'd reccomend getting a shift kit and a tranny cooler in there tho, you don't wanna be towing 5,000lbs and keeping the stock 3 second shift patterns... thats not good.

Otherwise, shes good to go.... these are awesome tow vehicles :).

Richard Miller
06-15-06, 08:10 AM
where could I find more info on the shift kit? any place /brand better than the next?

I~LUV~Caddys8792
06-15-06, 10:20 AM
That Coupe was mostly stock, the tranny was rebuilt with a shift kit, the cat was removed, and my father tweaked with it a bit for more power.... I'd reccomend getting a shift kit and a tranny cooler in there tho, you don't wanna be towing 5,000lbs and keeping the stock 3 second shift patterns... thats not good.


A shift kit for a '79 Cadillac?! So it'll chirp the tires when you're doing that 1-2 shift in the middle of your drag race?!

Can I get one for the '92? It's shifts are getting sloppy and I wanna quicken them up? How does it work? How do I install it?

Night Wolf
06-15-06, 11:04 AM
where could I find more info on the shift kit? any place /brand better than the next?

lol..... any hot rod supplier or store.... its a TH400, short tail, BOP-C bell housing (not that it makes a difference) you can get shift kits all over.... go to a good local shop, probably get one installed for 100 bucks.

Night Wolf
06-15-06, 11:09 AM
A shift kit for a '79 Cadillac?! So it'll chirp the tires when you're doing that 1-2 shift in the middle of your drag race?!

Can I get one for the '92? It's shifts are getting sloppy and I wanna quicken them up? How does it work? How do I install it?

lol... with the 425 being near stock, and 2.28 gears, and the 1-2 shift around 55mph... there will be no chriping of the tires :).

The transmission slips wayyy too much to begin with, that is the factory calibration so you don't feel the shifts at all.. that is excessive slippage on the clutches.... normally its not TOO bad... but start putting something that weighs as much as the '79 Cadillac, behind the '79 Cadillac... and.... its better to eliminate the extra stress... you'd be bruning up those clutches every time it shifts.

Yup, there are shift kits for the 4T60E..... LSD's too :). Your best bet would be to go to a local tranny shop and have them do it... for the 4T60E it may be around $150-$200... still, not too bad.

The 4T60E dosn't "need" it tho... by its design, the electronic part, and t shifts more firm then the Cadillac TH400. The Cadillacs with the TH400 had smoother shifting calibrations then the Rolls Royce cars that used them (Yup, RR had a contract with GM to run them) anything less then WOT and you could barely feel the shift.... WOT and "firm" dosn't exsist, it just... shifts.... while the RPM kinda fluently slides back and fourth between gears.

I~LUV~Caddys8792
06-16-06, 12:13 AM
A shift kit and a LSD in my '92?! Finally I could beat my friend's '93 Maxima SE thru a road course!

Night Wolf
06-16-06, 03:04 AM
I'll be putting both in the Coupe if (when) I get around to rebuilding the transmission later this year....

CadiJeff
06-16-06, 03:47 AM
hey Rick did something happen to your tranny or is it just "time for a rebuild"

The Ape Man
06-16-06, 06:07 AM
I have towed boats with this bodystyle over the years. It will pull the load just fine. Look online for Class 3 or 4 hitches. Make sure the radiator is clean inside and the clutch fan works properly. It's a good idea to have air shocks in order to adjust ride height while adjusting tongue weight. The factory auto level system is not going to be enough for higher tongue weights. Major concerns with anything over 4000 lbs will be sway and braking. You can pull plenty but it also has to stop. I once pulled a U-Haul trailer with another Cadillac loaded form Florida to NJ. A 4000 pound car pulling a 2000 lb trailer with another 4000 lb car on it. The whole trip was a nightmare. With weight balanced to eliminate sway, the assend of the lead vehicle was only 2 inches from the pavement. Factory level ride didn't lift it enough. There are online guides which give towing info from those who rent trailers etc.

Richard Miller
06-16-06, 08:16 AM
Ape Man, the factory auto level did not work that well, My car has the manual adjustment. Fill it up by the gas cap. Is that a better soulution than the auto? Are there heavy duty shocks to help with this.


thanks for the replies!

N0DIH
06-16-06, 01:15 PM
Olds had factory air pressure gauge and manual level adjust in 1976. Cadillac retained the auto level. Might be a nice touch, but hard to find these days.

Problem with auto level is if it is too heavy, the compressor will run and run and burn up, and I don't know if it is possible, but it could damage the shocks air chambers. Manual is best. Make sure the springs are up to the task, don't make the air shocks do all the work. This puts undesired stress on the shock mounts. I have heard of some breaking, although it is rare in my book.

GM spec'd my 94 Fleetwood with the factory towing package @ 840 lbs tongue weight max and up to 7000 lbs. If you have the factory 12in front brakes and 11inx2in rear drums, your brakes are up to the task. Your trans should be a THM400, that is excellent and the gears are the only weak point. I am not sure which gears you have, but the Fleetwoods had 2.28's and a 8.875" ring gear, and they don't have enough gear surface area to do heavy towing long, it could overstress the ring and pinion and cause breakage. I would recommend a 8.5" (you should have) with 3.08's to 3.42's minimum. This will cause some high rpms at cruise without OD though. So be mindful of the forces young padawan....

The Ape Man
06-16-06, 02:38 PM
Ape Man, the factory auto level did not work that well, My car has the manual adjustment. Fill it up by the gas cap. Is that a better soulution than the auto? Are there heavy duty shocks to help with this.


thanks for the replies!

Sounds like you already have the shocks that you need.

The Ape Man
06-16-06, 02:48 PM
Olds had factory air pressure gauge and manual level adjust in 1976. Cadillac retained the auto level. Might be a nice touch, but hard to find these days.

Problem with auto level is if it is too heavy, the compressor will run and run and burn up, and I don't know if it is possible, but it could damage the shocks air chambers. Manual is best. Make sure the springs are up to the task, don't make the air shocks do all the work. This puts undesired stress on the shock mounts. I have heard of some breaking, although it is rare in my book.

GM spec'd my 94 Fleetwood with the factory towing package @ 840 lbs tongue weight max and up to 7000 lbs. If you have the factory 12in front brakes and 11inx2in rear drums, your brakes are up to the task. Your trans should be a THM400, that is excellent and the gears are the only weak point. I am not sure which gears you have, but the Fleetwoods had 2.28's and a 8.875" ring gear, and they don't have enough gear surface area to do heavy towing long, it could overstress the ring and pinion and cause breakage. I would recommend a 8.5" (you should have) with 3.08's to 3.42's minimum. This will cause some high rpms at cruise without OD though. So be mindful of the forces young padawan....

Velly interesting. So the 8-7/8" ring and pinion has less surface area than other axles that fit these cars. Not heard this one before. Maybe the 8.5" is some sort of later truck gearset. Those cars will pull quite well with the factory 2.28:1. There is plenty of torque. Dropping in even a 2.73 will kill the cruise mileage. Been there. The 8-7/8" axle weighs at least 20 lbs more than the lighter units from comparable years.
I'd expect a later Brougham to be able to tow more as they are about 10% heavier than the average earlier 425 models. If the tow vehicle is too light then a sway problem might not adjust away so easily.
40 metres isn't working too well right now. Not much going on there. Lose that coax fed dipole for a good balanced tuner and heavy ladder line. You can get on 75/80 with a short antenna that way. The Z thing does work but any unbalance in the system will probably land you in TVI hell.

N0DIH
06-17-06, 12:27 PM
I didn't mean the 8.875(8 7/8) in has smaller, the uber tall gears do. There is so many less ring gear teeth on it and so many more on the pinion there is less actual surface to put load on and the ring gear is thinner. So it is more prone to breakage.

The guys with C/K1500 Suburbans/Tahoes/Pickups say the 8.5" ring gear is good for up to 6000 lbs on those vehicles (GM limit on the Sub), but when towing at that limit, they also see a lot of failures (they didn't say what failure though, from RV.net). The 8.5" isn't as strong as we would like. Even GM put the 8.6 in the pickups eventually, but not the Sub/Tahoe. The 9.5" semi floater came in the K2500 light truck with 7200 GVW. It is a 14 bolt and a LOT tougher than the 8.5/8.6 (aka 8 5/8"). There is also a 10.5" full floater 14 bolt too, but never for a car...

If you are serious about towing, get a 9.5" rear out of a limo. Katshot might remember what gearing they had on those.

I'll try to see if I can figure out something on 80M this weekend. I would lvoe to get on 160M.... Maybe my neighbors would let me run a wire from my yard to thiers!


Velly interesting. So the 8-7/8" ring and pinion has less surface area than other axles that fit these cars. Not heard this one before. Maybe the 8.5" is some sort of later truck gearset. Those cars will pull quite well with the factory 2.28:1. There is plenty of torque. Dropping in even a 2.73 will kill the cruise mileage. Been there. The 8-7/8" axle weighs at least 20 lbs more than the lighter units from comparable years.
I'd expect a later Brougham to be able to tow more as they are about 10% heavier than the average earlier 425 models. If the tow vehicle is too light then a sway problem might not adjust away so easily.
40 metres isn't working too well right now. Not much going on there. Lose that coax fed dipole for a good balanced tuner and heavy ladder line. You can get on 75/80 with a short antenna that way. The Z thing does work but any unbalance in the system will probably land you in TVI hell.

The Ape Man
06-18-06, 01:31 PM
I didn't mean the 8.875(8 7/8) in has smaller, the uber tall gears do. There is so many less ring gear teeth on it and so many more on the pinion there is less actual surface to put load on and the ring gear is thinner. So it is more prone to breakage.



Maybe. AFAIK The low numerical gears have less mechanical advantage and place less stress in the contact area. Torque isn't being multiplied at the expense of distance as much.

N0DIH
06-18-06, 03:28 PM
Under high loads on tall gears, as I understand it, the pinion really tries hard to climb up the ring gear. With a shorter gear, the pinion has less ability to do it, as the mechanical advantage is better, so it won't try to climb as much. A tough design like a Ford 9in is excellent for that, as it has a pinion bearing on both ends of the pinion, but the less desirable pinion to ring gear relationship makes the 9in not as efficient rear as a 10 bolt GM or 12 bolt GM.

Night Wolf
06-19-06, 12:51 AM
hey Rick did something happen to your tranny or is it just "time for a rebuild"

Well, it hasn't happened yet, but shes showing early signs of failure.... this failure may be 5k-50k away.... I am thinking more along the lines of 25k or so... which, isn't too bad if it did, I'd have the means to repair it by then

Tho as it is now, I am averaging 500miles/week or more.... miles are getting tacked in like nothing now.