Engine/Transmission (1994 - 1998) New Gear Vendors Instal Problems

[CNunema]

I had a Gear Vendors overdrive installed on my 97 dually a couple of months ago. I really like the unit but had to take it back because of a bad driveline vibration. I could tell when I got it home that the front shaft had way too much down angle. They also put in the wrong speed-o-meter gear. Speedo showed 65 at GPS speed of about 57. I changed the gear myself and it is within a couple of MPH now. Drove back to El Cajon and they cut the center bearing bracket and shortened it but I still get a vibration, especially above 60. I put my old drive shaft balancer back on today and noticed that the rear tube is a slightly smaller OD than my original. Anyone else have any problems with the Gear Vendors installation?

 

[LNaugle]

is it possible that since the install the 2 rear shafts are not at the same angle? they should be exactly the same. 1degree is ok. if more than that will cause a vibration on takeoff and at hiway speed

 

[CNunema]

All the information I have ever seen was that with a split drive shaft the front shaft should be within a half degree of level and straight horizontally and the rear shaft should take up difference in height and all the side to side difference. When the front shaft was at an almost equal down angle I had a very noticeable vibration above 60 MPH and a considerable launce shudder. When I convinced them to level the front shaft the launch shutter is completely gone with or without the 5th wheel on the truck but I still have a little vibration at higher speeds and it looks to me that the down angle on the front shaft is more than a half degree although I haven't measured it. I realize that the pinion angle changes a little when I put weight on the truck but the 5th wheel pin weight is only 960 lbs and only lowers the truck about an inch and a half. Sorry for the long post.



Edit: They tried to tell me that the problem was caused because I lowered the truck 3” to get bed clearance for the 5th wheel but there are two problems with that reasoning:

1. I lowered front and rear the same amount.

2. I didn't have any vibration or shudder before they changed the drive shaft.

 

[hsmith]

Don't cut them any slack. I did my own install, 2wd truck, with no issues on vibration. After replacing four units, I took mine out and was able to sell it. Nice unit, mine was smooth shifting with no problems other than could not get one to last long enough for me.

 

[CNunema]

The Gear Vendors looks to be a section of the old Turbo 400 with a sun gear arrangement and an add-on electric hydraulic pump for shifting. It would seem that the old Nash or US Gear unit would be more appropriate behind a standard transmission.



I figured for the $900 installation charge it would be a little more professional, oh well.



What kind of problems did you have with your Gear Vendors?

 

[hsmith]

They just didn't last pulling the fifth wheel. Got only around 55k out of one and it would shell out. Loved the unit, just not the life of it. They have a great exchange plan too.

 

[LNaugle]

Well maybe the shafts are not in sync with each other or just not balanced right

 

[RustyJC]

The Gear Vendors looks to be a section of the old Turbo 400 with a sun gear arrangement and an add-on electric hydraulic pump for shifting. It would seem that the old Nash or US Gear unit would be more appropriate behind a standard transmission.

The Gear Vendors unit is actually derived from the old Laycock de Normanville overdrive used on British cars, Volvos, etc. I agree that the Doug Nash/U. S. Gear overdrive would be more appropriate for standard transmissions, but unfortunately I understand that it's no longer in production.



A history is available HERE.

The vast majority of overdrives in European cars were manufactured by an English company called Laycock de Normanville (later GKN Laycock), at its Little London Road site in Sheffield, which is now demolished and remanufactured in the UK by an ex-Laycock de Normanville employee trading as Overdrive Spares. [2] The system was devised by a Briton, named Captain Edgar J de Normanville (1884-1968),[3] through a chance meeting with a Laycock Products Engineer. De Normanville overdrives were found in vehicles manufactured by Ford, British Leyland, Jaguar, Rootes Group and Volvo to name a few. Another British company, the former aircraft builder Fairey, built a successful all-mechanical unit for the Land Rover, which is still in production in America today.



The first production vehicle to feature the Laycock system was the 1948 Standard Vanguard Saloon. The first unit to be created was the A-type overdrive, which was fitted to many sports cars during the 1950s, and into the late 1960s. Several famous marques used A-type overdrives, including Jaguar, Aston Martin, Ferrari, Austin-Healey, Jensen, Bristol, AC, Armstrong Siddeley and Triumph's TR sports car range, until the end of TR5 & TR250 production in 1969.



In 1959, the Laycock Engineering Company introduced the D-type overdrive, which was fitted to a variety of motor cars including Volvo 120 and 1800s, Sunbeam Alpines and Rapiers, Triumph Spitfires, and also 1962-1967 MGBs (those with 3-synchro transmissions).



From 1967 the LH-type overdrive was introduced, and this featured in a variety of models, including 1968-1980 MGBs, the MGC, the Ford Zephyr, early Reliant Scimitars, TVRs, and Gilberns.



The J-type overdrive was introduced in the late 1960s, and was adapted to fit Volvo, Triumph, Vauxhall/Opel, American Motors and Chrysler motorcars, and Ford Transit vans.



The P-type overdrive marked the last updates and included both a Gear Vendors U. S. version and a Volvo version. The Volvo version kept the same package size as the J-type but with the updated 18 element freewheel and stronger splines through the planet carrier. The Gear Vendors U. S. version uses a larger 1. 375 outer diameter output shaft for higher capacity and a longer rear case.



Over a period of 40 years, Laycock Engineering manufactured over three and a half million overdrive Units, and over one million of these were fitted to Volvo motorcars.



In 2008 the U. S. company Gear Vendors, Inc. [4] of El Cajon, California purchased all the overdrive assets of GKN to continue production of the U. S. version and all spares for J and P types worldwide.



The system features an oil pressure operated device attached to the back of the standard gearbox operating on the gearbox output shaft. Through a system of oil pressure, solenoids and pistons, the overdrive would drop the revs on whatever gears it was used on by 22% (. 778). For instance, the overdrive system applied to a Triumph TR5 operates on 2nd, 3rd and top gear. When engaged, the overdrive would drop the revs from 3000 by 666 RPM, or from 3500 the drop would be 777 RPM to 2723 net. The advantages this reduced rpm had on fuel consumption was most often quite near 22% decrease during highway driving.

Rusty

 

[hsmith]

You are correct about US Gear. They got bought out, don't remember by who. It was a real tough unit for sure.

 

[CNunema]

I put the Balance Master back on the rear shaft and moved it about 7 inches back from the front joint on the rear shaft and now only a very slight vibration so you may be right but the front shaft still has too much of a down angle. When I get some time I'll take it to a drive line shop and have it done right. I also found that the rear tube is noticeably thinner and slightly smaller OD than the original.

 

[CNunema]

The Gear Vendors unit is actually derived from the old Laycock de Normanville overdrive used on British cars, Volvos, etc. I agree that the Doug Nash/U. S. Gear overdrive would be more appropriate for standard transmissions, but unfortunately I understand that it's no longer in production.



A history is available HERE







Rusty

Good find. That's interesting. Thanks